IPAC2011 - List of Keywords (electron)

Paper	Title	Other Keywords	Page
MOYBA01	Present Status of the ILC Project and Developments	cavity, linac, linear-collider, collider	16
	M.C. Ross Fermilab, Batavia, USA N.J. Walker DESY, Hamburg, Germany A. Yamamoto KEK, Ibaraki, Japan
	Funding: FNAL is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The Technical Design of the ILC Project will be finished in late 2012. The Technical Design Report will include a description of the updated design, with a cost estimate and a project plan, and the results of R & D done in support of the ILC. Results from directed ILC R & D are used to reduce the cost and risk associated with the ILC design. We present a summary of key challenges and show how the global R & D effort has addressed them. The most important activity has been in pursuit of very high gradient superconducting RF linac technology. There has been excellent progress toward the goal of practical industrial production of niobium sheet-metal cavities with gradient performance in excess of 35 MV/m. In addition, three purpose-built beam test facilities have been constructed and used to study and demonstrate high current linac performance, electron-cloud beam dynamics and precision beam control. The report also includes a summary of component design studies and conventional facilities cost optimization design studies.
	Slides MOYBA01 [9.755 MB]

MOYCA01	Status Report on the Commissioning of the Japanese XFEL at SPring-8	laser, undulator, acceleration, FEL	21
	H. Tanaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	The Japanese XFEL at SPring-8, which was named SACLA (Spring-8 Angstrom Compact free electron LAser), was completed in FY2010. After RF full-power aging for about four months the beam commissioning of SACLA has been started since 21 February 2011. About one month later, in 23 March a design beam energy of 8 GeV was achieved and a spontaneous undulator radiation of 0.8 Angstrom was observed at the beam-line optical hutch by closing XFEL undulator gaps down to 5 mm in full-width. The beam commissioning has proceeded smoothly and since the middle of April we have entered to a tuning phase towards SASE lasing, which is at least one month ahead of schedule. This talk will report the beam commissioning overview of SACLA including SASE XFEL performance, key tuning-processes and critical issues for achieving the lasing.
	Slides MOYCA01 [37.840 MB]

MOOCA03	Updates to the International Linear Collider Damping Rings Baseline Design	lattice, damping, positron, cavity	32
	S. Guiducci, M.E. Biagini INFN/LNF, Frascati (Roma), Italy G. Dugan, M.A. Palmer, D. L. Rubin CLASSE, Ithaca, New York, USA J. Gao, D. Wang IHEP Beijing, Beijing, People's Republic of China M.T.F. Pivi, Y. Sun SLAC, Menlo Park, California, USA J. Urakawa KEK, Ibaraki, Japan
	A new baseline design for the International Linear Collider (ILC) damping rings has been adopted which reduces the ring circumference to 3.2 km from 6.4 km. This design change is associated with a revised plan to operate the ILC with one half the beam current originally specified in the ILC Reference Design Report. We describe the new layout and lattice that has been developed for the shorter ring. In addition, we discuss features of the new design that will allow operation at a 10Hz repetition rate which is twice the rate specified for baseline operation. Finally, we examine the implications for restoring operation with the originally specified beam current while maintaining the smaller ring circumference.
	Slides MOOCA03 [2.381 MB]

MOOCB02	Commissioning and Performance of the Beam Monitor System for XFEL/SPring-8 “SACLA”	cavity, undulator, bunching, FEL	47
	Y. Otake, C. Kondo, H. Maesaka RIKEN Spring-8 Harima, Hyogo, Japan H. Ego, S. Matsubara, T. Matsumoto, T. Sakurai, H. Tomizawa, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan S.I. Inoue SES, Hyogo-pref., Japan
	The construction of a beam monitor system for XFEL/SPring 8 “SACLA” was completed. The system was developed to realize a spatial resolution of less than 3 um to align a beam orbit for an undulator section with about 100 m long and a temporal resolution to measure bunch lengths from 1 ns to 30 fs to maintain a constant peak beam current conducting stable SASE lasing. The system principally comprises cavity type beam position monitors (BPM), current monitors (CT), screen monitors (SCM) and bunch length measurement instruments, such as an rf deflector and CSR detectors. Commissioning of SACLA started from March 2011, and the monitors performed sufficient roles to tune beams for the lasing. The achieved over-all performances of the system including DAQ are: the BPM have spatial resolution of 300 nm, the bunch length monitors observe bunch lengths from 1ns in an injector with velocity bunching to less than 30 fs after three-stage bunch compressors. The less than a 3 um spatial resolution of the SCM was also confirmed in practical beam operation. By these fulfilled performances, the stable lasing of SACLA will be achieved. This report describes commissioning, performance of the system.
	Slides MOOCB02 [7.516 MB]

MOODB02	RF Modeling Plans for the European Spallation Source	cavity, HOM, beam-losses, linac	56
	S. Molloy, M. Lindroos, S. Peggs ESS, Lund, Sweden R. Ainsworth Royal Holloway, University of London, Surrey, United Kingdom R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden
	The European Spallation Source (ESS) will be the world's most powerful next generation neutron source. The ESS linac is designed to accelerate highly charged bunches of protons to a final energy of 2.5 GeV, with a design beam power of 5 MW, for collision with a target used to produce the high neutron flux. In order to achieve this several stages of RF acceleration are required, each using a different technology. The high beam current and power require a high degree of control of the accelerating RF, and the specification that no more than 1 W/m of losses will be experienced means that the excitation and decay of the HOMs must be very well understood. Experience at other high power machines also implies that an understanding of the generation and subsequent trajectories of any field-emitted electrons should be understood. Thermal detuning of the HOM couplers due to multipacting is a serious concern here. This paper will outline the RF modeling plans - including the construction of mathematical models, simulations of HOMs, and multipacting - during the current Accelerator Design Update phase, and will discuss several of the more important issues for ESS.
	Slides MOODB02 [48.641 MB]

MOPC009	Design of a Pi/2 Mode S-Band Low Energy TW Electron Linear Accelerator	coupling, acceleration, linac, simulation	80
	H. Shaker IPM, Tehran, Iran F. Ghasemi sbu, Tehran, Iran H. Shaker CERN, Geneva, Switzerland
	This design is related to a Pi/2 mode S-Band low energy TW electron linear accelerator which is in the construction stage. This project is supported by the school of particles and accelerators, institute for research in fundamental sciences (IPM), Tehran, Iran. This design consists of a buncher and an accelerating structure that are joined and two couplers for the input/output feedings. At each design stage, different methods (analytical or numerical) are used to confirm the results and also to have a better understanding.

MOPC018	Operation Status of C-band High Gradient Accelerator for XFEL/SPring-8 (SACLA)	accelerating-gradient, klystron, acceleration, target	104
	T. Inagaki, C. Kondo, T. Ohshima, Y. Otake, T. Sakurai, K. Shirasawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Shintake RIKEN Spring-8 Harima, Hyogo, Japan
	XFEL project in SPring-8 have constructed a compact XFEL facility. In order to shorten an accelerator length, a C-band (5712 MHz) accelerator was employed due to a higher accelerating gradient than that of an S-band accelerator. Since a C-band accelerating structure generates a gradient of higher than 35 MV/m, the total length of an 8 GeV accelerator fits within 400 m, including 64 C-band RF units, 4 S-band RF units, an injector and three bunch compressors. The accelerator components were carefully installed by September 2010. Then we have performed high power RF conditioning. After 500 hours of the conditioning, the accelerating gradient of each C-band structure was reached up to 35 MV/m without any particular problem. The RF breakdown rate is low enough for an accelerator operation. Since February 2011, we started the beam commissioning for XFEL. The C-band accelerator has accelerated the electron beam up to 8 GeV, with an accelerating gradient of 33-35 MV/m in average. The energy and the trajectory of the electron beam was stable, thanks to the stabilization of a klystron voltage of 350 kV within 0.01% by a high precision high voltage charger. The facility was recently named SACLA (SPring-8 Angstrom Compact free electron LAser).

MOPC020	Development of an S-band Multi-cell Accelerating Cavity for RF Gun and Booster Linac	gun, cavity, booster, linac	110
	T. Aoki, K. Sakaue, M. Washio RISE, Tokyo, Japan A. Deshpande SAMEER, Mumbai, India M.K. Fukuda, N.K. Kudo, T. Takatomi, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by JST Quantum Beam Program We have been developing a photocathode rf gun. The rf gun with multi cell can produce a high energy electron beam, so it may be used for numerous applications such as medicine and industry. At Laser Undulator Compact X-ray source (LUCX), we have developed a compact X-ray source based on inverse Compton scattering. Using a multi cell rf gun will make possible for the X-ray source to use for such applications. S-band 3.5 cell rf electron gun which is 20 cm long can produce more than 10 MeV electron beam. According to the simulation, it is said that the emittance of 3.5 cell rf gun is as low as that of 1.6 cell rf gun. The electromagnetic design has been performed with the code SuperFish, and the particle tracing by Parmela. The new rf gun is already installed and produced a high quality electron beam with energy of more than 10 MeV. As a consequence of the substantial efforts of developing rf cavity, we decide to make a compact RF accelerating structure with more cell for achieving a smaller system. The measurement results of using the 3.5 cell rf gun, the design of 12 cell booster cavity, and current status of 12 cell cavity manufacturing will be presented at the conference.

MOPC022	Development of a Compact C-band Photocathode RF Gun	gun, cathode, injection, emittance	116
	X.H. Liu, H. Chen, W.-H. Huang, H.J. Qian, C.-X. Tang, Z. Zhang TUB, Beijing, People's Republic of China
	Funding: This work is supported by National Natural Science Foundation of China and National Basic Research Program of China (973 Program). A C-band photocathode RF gun for a compact electron diffraction facility is developed in Tsinghua University, which is designed to work at the frequency of 5.712GHz. This paper presents the physics and structure design of this C-band RF gun, and the comparison on beam dynamics of S-band and C-band photoinjector has been done. Some new structure design will be adopted in this gun, including the optimized cavity length and elliptical iris, which is helpful to achieve lower emittance and larger mode separation.

MOPC023	Design of a C-band 6 MeV Standing-wave Linear Accelerating Structure	coupling, bunching, impedance, simulation	119
	J.H. Shao, H. Chen, Q.Z. Xing TUB, Beijing, People's Republic of China
	We design a C-band standing-wave biperiodic on-axis coupled linear accelerating structure for industrial and medical applications. It’s less than 300mm long; consists of 3 bunching cells and 9 normal cells. It can accelerate electrons to 6MeV and the pulsed beam current is 100mA. The RF power source is a 2.5MW magnetron. We implement 2D cells geometry optimization by SUPERFISH, beam dynamics study by PARMELA and full scale 3D calculations by MAFIA codes.

MOPC029	Development of Injector for Compact FEL Tera-hertz Source in CAEP	gun, FEL, booster, simulation	131
	W. Bai, M. Li, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	This paper introducs the development of a injector for compact FEL tera-hertz source at Institute of Applied Electronics in China Academy of Engineering Physics (IAE/CAEP). The injector consist of a main accelerator for energy booster section and a multicavity thermionic-cathode rf gun with low back bombardment, with total length no more than one meter. Numerical simulation result shows that the back bombardment power is less for the thermionic-cathode rf gun of the injector and the main accelerator has a good performance, which can provide high quality electron beam with emittance about 10 pi mm mrad, energy about 7 MeV and energy spread about 1%. At present, the preliminary hot test experiment on the injector has been done. The test results indicate that the mainly tested parameters agree well with the theoretical design ones. The process of the preliminary hot test experiment on the injector is present in this paper.

MOPC034	Design of a 0.6-cell Cell Photocathode RF Gun for FED	gun, simulation, cathode, solenoid	145
	Y.W. Parc, M.S. Chae, I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea
	Final goal of this study is the development of single cell radio-frequency (RF) electron gun which is optimized to the femotosecond electron diffraction. This study will open new technology basis for the laboratory research in the femto-second (fs) chemistry at the university. RF electron gun will be fabricated with single cell which will reduce the cost and effort. We will also conduct a simulation study to find an optimized operation condition of the RF gun to provide the best electron beam to the femtosecond electron diffraction experimentalist. In this presentation, we will show the status of the RF gun development. The results with the simulation code PARMELA will be presented to find the optimal operation condition of the single cell RF gun for FED.

MOPC035	Design and Machine Features of 2.2-m C-band Accelerating Structure	cavity, accelerating-gradient, linac, vacuum	148
	C.H. Yi, M.-H. Cho, S.H. Kim, H. Lee POSTECH, Pohang, Kyungbuk, Republic of Korea W. Namkung PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This work is partly supported by the MEST, Korea and POSTECH BK21 Program. And this work was supported by the Korea Student Aid Foundation (KOSAF) grant funded by the Korea government. A compact linac system is designed using a longer accelerating column in a C-band linac. It reduces the total number of RF units for the given linac beam energy and results in the cost-effective use of RF powers. For the 10 GeV PAL-XFEL project, a C-band accelerating column of 2.2-m long is investigated, which is 22% longer than 1.8-m for the SACLA at SPring-8. The detailed RF and thermal characteristics are presented by an analytic model.

MOPC041	Cross-Field Multipactor Discharge in the X-Band Cylindrical Cavity	cavity, multipactoring, vacuum, radiation	166
	S.V. Kuzikov, E.V. Ilyakov, I.S. Kulagin, A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia D. Lee NSRRC, Hsinchu, Taiwan
	The paper represents the experimental study of one-sided cross-field multipactor discharge in the copper cavity with the operating mode TM01 in external DC magnetic field. It was shown that discharge is very sensible to magnitudes of the external magnetic field and rf fields as well. At proper fields the multipactor discharge can be developed for 15 ns and the electron concentration can be comparable with critical one for the given rf frequency. As a result of discharging, the cavity changes its own resonant frequency and can play a role of a switch which can substitute full transmission by full reflection. Switching parameters could be controlled by DC magnetic field as well as by additional rf radiation at different frequency than operating frequency. The high rf absorption of multipactor discharge also can be used in electrically controlled powerful loads and attenuators.

MOPC050	Multipacting Analysis for the Superconducting RF Cavity HOM Couplers in ESS	cavity, simulation, HOM, superconducting-RF	190
	S. Molloy ESS, Lund, Sweden R. Ainsworth Royal Holloway, University of London, Surrey, United Kingdom R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden
	The European Spallation Source (ESS) linac will consist of three families superconducting RF cavities to accelerate protons to the required 5 MW for collision with the target. If it is determined that HOM damping is required to limit the effect of beam induced modes, it is quite likely that HOM couplers will be installed. Multipacting in these couplers is a concern as thermally induced detuning of the fundamental notch filter has limited the achievable gradient in other high power machines. It is therefore important to avoid potential multipacting conditions during the design phase. Presented here are simulations using the Track3P code developed at SLAC. Multipacting regions are highlighted, electron trajectories are shown, and suitability of the proposed HOM coupler design is discussed.

MOPC059	The Plane Wave Transformer Linac Development at NSRRC	linac, simulation, impedance, cavity	217
	A. Sadeghipanah, J.-Y. Hwang, W.K. Lau NSRRC, Hsinchu, Taiwan T.H. Chang NTHU, Hsinchu, Taiwan
	A Plane-Wave-Transformer (PWT), standing wave linac operating at S-band frequency (2.9979 GHz) is being developed at NSRRC. This structure offers the advantages of high efficiency, compactness, fabrication simplicity and cost. The PWT prototype at NSRRC consists of three cells with two half-cells at the ends, separated by a set of four flat disks suspended and cooled by four water tubes inside a large cylindrical tank. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 2-D code SUPERFISH and 3-D code MAFIA. In this paper, we describe the principle properties of this structure, the electric parameters obtained from numerical simulations, and heat dissipation calculation. The mechanical design for prototype linac is also reported.

MOPC060	Bunching-frequency Multiplication for a THz Pulse-train Photoinjector	bunching, linac, laser, acceleration	220
	Y.-C. Huang, F.H. Chao, C.H. Chen, K.Y. Huang NTHU, Hsinchu, Taiwan
	Funding: This work is supported by National Science Council under Contract NSC 99-2112-M-007 -013 -MY3. A THz-pulse-train photoinjector* employs a THz-pulse-train laser as its driver laser to generate a beam with a bunching frequency in the THz range. However a laser frequency is on the order of a few hundred THz. It is not possible to generate a beam from the pulse-train photoinjector with a bunching frequency exceeding the laser’s carrier frequency. In view of the strong demand for a compact x-ray free-electron laser (FEL), it is highly desirable to multiply the bunching frequency of the beam from a pulse-train injector to the x-ray frequencies. We propose to chirp the energy of the THz electron pulse train in an accelerator and compress the whole beam in a magnet to increase the electron bunching frequency. Our study shows a compression ratio or a bunching-frequency multiplication factor of a few tens is achievable from a properly designed magnetic chicane compressor. The bunching factor, however, is unfortunately degraded due to the energy chirp, emittance growth, and wake-field generation. In the conference, we will show that a bunching factor of a few ppm in the bunch-frequency multiplied beam is sufficient to build up the FEL power from a 10-time length reduced undulator. * Y. C. Huang, “Laser-beat-wave bunched beam for compact superradiance sources,” International Journal of Modern Physics B, Vol. 21 Issue 3/4, p277-286 (2007).

MOPC065	Ion Motion in the Vicinity of Microprotrusions in Accelerating Structures	ion, simulation, plasma, background	232
	D.G. Kashyn, T.M. Antonsen, I. Haber, G.S. Nusinovich UMD, College Park, Maryland, USA
	Funding: This work is supported by Office of High Energy Physics of the U.S. Department of Energy. It is known that newly fabricated accelerating structures have almost ideally smooth surface. However, ‘post mortem’ examination of these structures reveals that their surface can be significantly modified after high-gradient operation. This surface modification can be caused by the appearance of microscopic protrusions. One of the factors leading to heating, melting and evaporation of these protrusions (factors resulting in the RF breakdown) is ion bombardment. In our study we analyze ion motion in the vicinity of microprotrusions both analytically and numerically. First, we study the ion motion in the RF electric field magnified by the protrusion in the absence of electron field emitted current and show that most of the ions do not reach the structure surface. Then we add into consideration the interaction of ions with Fowler-Nordheim current emitted from the tip of protrusion (dark current). First, we develop a model describing this interaction and then we supplement it with numerical results using PIC code WARP*. We show that the ions move towards the area occupied by the dark current, but this does not increase the bombardment of micro-protrusions. R.B. Palmer,et al, Phys. Rev ST Accel. Beams 12, 031002 (2009). P. Wilson, AIP Conf. Proc., 877, Melville, New York, 2006, p. 27. *J.-L. Vay, et al, Physics of Plasmas, 11, 2928 (2004).

MOPC067	X-Band Test Station at Lawrence Livermore National Laboratory	klystron, cathode, laser, brightness	235
	R.A. Marsh, F. Albert, S.G. Anderson, C.P.J. Barty, G.K. Beer, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck LLNL, Livermore, California, USA C. Adolphsen, A.E. Candel, T.S. Chu, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou SLAC, Menlo Park, California, USA
	Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. An X-band multi-bunch test station is being built at LLNL to investigate the science and technology paths required to boost the current mono-energetic gamma-ray (MEGa-Ray) brightness by orders of magnitude. The test station will consist of a 5.5 cell X-band RF photoinjector, single accelerator section, and beam diagnostics. Beam quality must be exceedingly high in order to produce narrow-bandwidth gamma-rays, requiring a robust state of the art photoinjector. The photoinjector will be a high gradient (200 MV/m peak surface field on the cathode) standing wave structure, featuring a dual feed racetrack coupler, elliptical irises, and an optimized first cell length. A solid-state Scandinova modulator will power a single SLAC XL4 11.424 GHz 50 MW klystron. RF distribution will allow for full powering of the photoinjector with the balance of the RF powering a single accelerator section so that the electron parameters can be measured. The status of the facility will be presented including commissioning schedule and first experiment plans. Future experimental programs pertinent to Compton scattering R&D, high gradient structure testing, and light source development will be discussed.

MOPC071	Status of High Power Tests of Normal Conducting Short Standing Wave Structures*	coupling, klystron, status, beam-loading	241
	V.A. Dolgashev, Z. Li, S.G. Tantawi, A.D. Yeremian SLAC, Menlo Park, California, USA Y. Higashi KEK, Ibaraki, Japan B. Spataro INFN/LNF, Frascati (Roma), Italy
	Funding: Work Supported by Doe Contract No. DE-AC02-76SF00515 We report results of continuing high power tests of short standing wave structures. These tests are part of an experimental and theoretical study of basic physics of rf breakdown in 11.4 GHz, normal conducting structures. The goal of this study is to determine the accelerating gradient capability of normal conducting rf powered particle accelerators. We have tested structures of different geometries, cell joining techniques, and materials. We found that the breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for cylindrically symmetric structures powered via a TM01 mode launcher. We report test results for structures powered by side-coupled rectangular waveguides. We found that increased rf magnetic field due to the side-coupling increases the breakdown rate as compared to the same accelerating gradient in cylindrically symmetric structures.

MOPC073	A Dual-mode Accelerating Cavity to Test RF Breakdown Dependence on RF Magnetic Fields	cavity, simulation, radio-frequency, vacuum	247
	A.D. Yeremian, V.A. Dolgashev, J. Neilson, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: * Work Supported by Doe Contract No. DE-AC02-76SF00515 RF Breakdown experiments on short accelerating structures at SLAC have shown that increased rf magnetic fields increase the probability of rf breakdowns. Moreover, the breakdown rate is highly correlated with the peak pulse-heating in soft-copper single-cell standing-wave structures of disk-loaded waveguide type. In these geometries the rf electric and magnetic fields are highly correlated. To separate effects of rf magnetic and electric fields on the rf breakdown rate, we have designed an X-band cavity with a geometry as close to that of a standing-wave accelerator cell as practically possible. This cavity supports two modes: an accelerating TM mode and a TE mode with no-surface-electric field but with a strong magnetic field. The cavity will be constructed and tested at the Accelerator Structure Test Area (ASTA) at SLAC.

MOPC082	Status of the 325 MHz SC CH-Cavity at IAP Frankfurt	cavity, simulation, linac, status	265
	M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany M. Amberg, K. Aulenbacher HIM, Mainz, Germany W.A. Barth, S. Mickat GSI, Darmstadt, Germany
	Funding: BMBF contract no. 06FY161I At the Institute for Applied Physics (IAP), University of Frankfurt, a s.c. 325 MHz CH-Cavity is under development for future beam tests at GSI UNILAC, Darmstadt. The cavity with 7 accelerating cells has a geometrical beta of 0.15 corresponding to 11.4 AMeV. The design gradient is 5 MV/m. The geometry of this resonator was optimized with respect to a compact design, low peak fields, surface processing, power coupling and tuning. Furthermore a new tuning system based on bellow tuners inside the resonator will control the frequency during operation. After rf tests in Frankfurt the cavity will be tested with a 10 mA, 11.4 AMeV beam delivered by the GSI UNILAC. In this paper rf simulations, multipacting analysis as well as thermal calculations will be presented.

MOPC092	Effect of Current Densities on Sulfur Generation at Electropolished Niobium Surface	cavity, niobium, cathode, vacuum	292
	P.V. Tyagi Sokendai, Ibaraki, Japan H. Hayano, S. Kato, M. Nishiwaki, T. Noguchi, T. Saeki, M. Sawabe KEK, Ibaraki, Japan
	We conducted a series of electropolishing (EP) experiments in aged EP acid with high (≈50 mA/cm²) and low (≈30 mA/cm²) current densities on Nb surfaces. The experiments were carried out both for laboratory coupons and a real Nb single cell cavity with six witness samples located at three typical positions (equator, iris and beam pipe). All the samples surface were investigated by XPS (x-ray photoelectron spectroscopy), SEM (scanning electron microscope) and EDX (energy dispersive x-ray spectroscopy). The surface analysis showed the EP with a high current density produced a huge amount sulfate particles at Nb surface whereas the EP with a low current density is very helpful to mitigate sulfate at Nb surface in both the experiments.

MOPC093	Novel Field Emission Scanner for Surface Study of Niobium SRF Cavity	cavity, SRF, site, controls	295
	S. Kato, M. Nishiwaki, T. Noguchi KEK, Ibaraki, Japan V. Chouhan GUAS, Kanagawa, Japan P.V. Tyagi Sokendai, Ibaraki, Japan
	It is mandatory to investigate field emission on Nb SRF cavity systematically since strong field emission often limits the cavity performance. The field emission strength and the number of emission sites strongly depend on Nb surface properties which are determined by its surface treatment and handling. Field emission scanner (FES) developed allows us to measure a distribution of the field emitting sites over a sample surface at a given field strength along with its FE-SEM observation and energy dispersive x-ray analysis. FES consists of an anode needle driven by precise 3D stepping motors and an eucentric sample stage. The compact scanner was installed into the space between the object lens and the SEM sample holder. In addition, this system was newly equipped with a sample load-lock system for existing UHV suitcases. Therefore a sample coupon to be observed is hardly exposed to contaminants and dust particles during the transportation. In-situ heating of a sample coupon can be done during an experiment to simulate a baking process of a SRF cavity. This article describes development of the field emission scanner and its preliminary results of the application to niobium samples.

MOPC101	Vertical Test of PEFP Prototype SRF Cavity	cavity, accelerating-gradient, linac, SRF	307
	H.S. Kim, Y.-S. Cho, H.-J. Kwon KAERI, Daejon, Republic of Korea
	Funding: This work was supported by Ministry of Education, Science and Technology of the Korean Government. The PEFP Proton linac is a 100-MeV machine which consists of a proton injector, a 3-MeVRFQ and 100-MeV DTL. For the extension of the machine beyond 100 MeV, SRF technology is under consideration. As a prototyping activity, a superconducting RF cavity with a geometrical beta of 0.42 and a resonant frequency of 700 MHz has been designed, fabricated and tested. The cavity is an elliptical shape with 5 cells stiffened by double-ring structure. A design accelerating gradient is 8.0 MV/m at the operating temperature of 4.2 K and maximum duty factor is 9%. For the vertical test of the cavity, a cryostat with a vacuum jacket and multi-layer insulation was prepared. The RF system for driving the cavity is based on PLL to track the resonant frequency. In case of lack of RF power, a two-way RF power combiner based on splitted coaxial transmission line is considered. The details of the vertical test setup and test results will be presented in this paper.

MOPC112	Fabrication and Testing Status of CEBAF 12 GeV Upgrade Cavities	cavity, cryomodule, HOM, status	337
	F. Marhauser, A. Burrill, G.K. Davis, D. Forehand, C. Grenoble, J. Hogan, R.B. Overton, A.V. Reilly, R.A. Rimmer, M. Stirbet JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The 12 GeV upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) is under way. All cavities have been built by industry and are presently undergoing post-processing and final low and high power qualification before cryomodule assembly. The status is reported including fabrication-related experiences, observations and issues throughout production, post-processing and qualification.

MOPC114	Design, Fabrication and Testing of Medium-Beta 650 MHz SRF Cavity Prototypes for Project-X	cavity, SRF, linac, vacuum	343
	F. Marhauser, W.A. Clemens, J. Henry, P. Kneisel, R. Martin, R.A. Rimmer, G. Slack, L. Turlington, R.S. Williams JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. A new type of superconducting radio frequency (SRF) cavity shape with a shallow equator dome to reduce electron impact energies for suppressing multipacting barriers has been proposed. The shape is in consideration for the first time in the framework of Project-X to design a potential multi-cell cavity candidate for the medium-beta section of the SRF proton CW linac operating at 650 MHz. Rationales covering the design of the multi-cell cavity, the manufacture, post-processing and high power testing of two single-cell prototypes are presented.

MOPC116	Development of Nb and Alternative Material Thin Films Tailored for SRF Applications	SRF, ECR, cavity, ion	349
	A-M. Valente-Feliciano, H.L. Phillips, C.E. Reece, J.K. Spradlin, B. Xiao, X. Zhao JLAB, Newport News, Virginia, USA H. Baumgart, D. Gu ODU, Norfolk, Virginia, USA D. Beringer, R.A. Lukaszew The College of William and Mary, Williamsburg, USA K.I. Seo NSU, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S.DOE Contract No. DE-AC05-06OR23177. Over the years, Nb/Cu technology, despite its shortcomings due to the commonly used magnetron sputtering, has positioned itself as an alternative route for the future of superconducting structures used in accelerators. Recently, significant progress has been made in the development of energetic vacuum deposition techniques, showing promise for the production of thin films tailored for SRF applications. JLab is pursuing energetic condensation deposition via techniques such as Electron Cyclotron Resonance and High Power Impulse Magnetron Sputtering. As part of this project, the influence of the deposition energy on the material and RF properties of the Nb thin film is investigated with the characterization of their surface, structure, superconducting properties and RF response. It has been shown that the film RRR can be tuned from single digits to values greater than 400. This paper presents results on surface impedance measurements correlated with surface and material characterization for Nb films produced on various substrates, monocrystalline and polycrystalline as well as amorphous. A progress report on work on NbTiN and AlN based multilayer structures will also be presented.

MOPC123	Temperature Dependent Microphonics in the BNL Electron Cooler*	resonance, cavity, linac, cryogenics	370
	P. Jain Stony Brook University, Stony Brook, USA I. Ben-Zvi, C. Schultheiss BNL, Upton, Long Island, New York, USA
	An R&D Energy Recovery Linac (ERL), to be used in the BNL electron cooler, has been operational in a developmental setting. The ERL requires a cryogenic system to supply cooling to a superconducting RF gun and the 5-cell superconducting RF cavity system that is kept cold at 2K. The 2K superfluid bath is produced by pumping on the bath using a sub-atmospheric warm compression system. During a test run in October 2010, a resonance peak corresponding to a noise of 30 Hz was observed at 1.88K. This noise peak, present at all temperatures below 2K, is assumed to be of mechanical origin from the vibration of the cryopump. Another resonance noise peak of 16 Hz, characteristic of the system, was observed at 1.98K, which shifted towards the 30 Hz peak as the temperature of the cryostat varied from 1.98K to 1.88K. The 16 Hz resonance peak upon hitting the 30 Hz resonance peak, sets a resonance condition, thereby the 30 Hz peak getting amplified by more than five times. In this paper we explore the origin of the temperature dependent 16 Hz resonance peak and give a physical explanation of the resonance.

MOPC134	Multifrequency High Power Microwave Electric-vacuum Devices	klystron, vacuum, acceleration, cavity	391
	K.G. Simonov, A.A. Borisov, A.V. Galdetsky, A.N. Korolev, A.V. Mamontov ISTOK, Moscow Region, Russia O.A. Morozov Research and Production Co. "MAGRATEP", Fryazino, Russia
	A new approach for the design of the multifrequency high power microwave vacuum devices is proposed. These devices provide simultaneously some output phased signals with operating frequencies ω, 2 ω, , nω while input frequency is ω. For example, it is possible obtain output power at frequencies ω and 2ω by using of double-gap output resonator tuned on two modes – sinphased mode at 2ω and antiphased mode at frequency ω. It is possible obtain power at four frequencies ω, 2ω, 3ω and 6ω by using of the two double-gap output resonators placed one inside the other. It is possible obtain power at multiple frequencies by using of the special coaxial resonator. A microwave vacuum device has been fabricated in which power was extracted at nine multiple frequencies simultaneously. The output signal has form of pulses with ultrashort duration and superhigh repetition frequency equal to the input signal frequency ω. Multifrequency high power microwave vacuum devices can be used for the development of compact accelerators of charged particles.

MOPC138	Practical Test of the Linac4 RF Power System	klystron, linac, cavity, controls	403
	N. Schwerg, O. Brunner CERN, Geneva, Switzerland
	Linac4 is a linear accelerator for negative Hydrogen ions which will replace the old Linac2 as injector for the CERN accelerators. Its higher energy of 160 MeV will increase the beam intensity in the downstream machines. The normal-conducting accelerating structures are housed in a 100 m long tunnel which will be connected to the existing chain of accelerators and can be extended into a new injector chain. The high RF power for the Linac4 accelerating structures will be generated by thirteen 1.3 MW klystrons, previously used for the CERN LEP accelerator, and six new klystrons of 2.8 MW all operating at a frequency of 352.2 MHz. The re-use of existing LEP equipment, space limitations in the installation and tight phase and amplitude constraints pose a number of challenges for the integration of the RF power system. The power distribution scheme features a folded magic-tee feeding the power from a 2.8 MW klystron to two LEP circulators. We present first results from the Linac4 test place, validating the approach and the used components as well as reporting on the klystron re-tuning activities.

MOPC144	Autocorrelation Function and Power Spectrum of a Train of Quasiperiodic Sequence of Pulses	FEL, wakefield, free-electron-laser, optics	415
	E.M. Laziev, B. Grigoryan, V.M. Tsakanov CANDLE, Yerevan, Armenia M. Movsisyan, D.L. Oganesyan YSU, Yerevan, Armenia
	The statistical relationship of the autocorrelation function and spectrum of a train of quasi-periodic sequence of pulses having a time jitter of the repetition rate is obtained. Presented the accordance of autocorrelation function as well as power spectrum of the bounded quasi-periodic sequence of pulses and timing jitter of their repetition rate. The results can be used at the measurements of timing jitter of a train of electron bunches.

MOPC148	Optical Clock Distribution System at the ALICE Energy Recovery Linac	pick-up, laser, FEL, feedback	427
	T.T. Ng, S.P. Jamison STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Highly stable clock distribution across future light sources is important for the synchronisation of beam generation, manipulation and diagnostics with photon experiments. Optical fibre technology can be used to combat the stability challenges in distributing clock signals over long distances with coaxial cable. We report here on the status of the optical clock distribution system installed on the ALICE energy recovery linac which uses the propagation of ultra-short optical pulses to carry the clock signal. We also present the characterisation of a beam arrival monitor suitable using <40 pC bunch charges and 7 mW, sub-100 fs distributed clock pulses.

MOPC154	RF Photo Gun Stability Measurement at PITZ	gun, laser, feedback, cavity	442
	I.I. Isaev, H.-J. Grabosch, M. Gross, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria M. Hoffmann, H. Schlarb DESY, Hamburg, Germany M.A. Khojoyan YerPhI, Yerevan, Armenia D. Richter HZB, Berlin, Germany A. Shapovalov NRNU MEPHI, Moscow, Russia I.H. Templin, I. Will MBI, Berlin, Germany
	The stability of the RF phase in the RF photo injector gun is one of the most important factors for the successful operation of linac based free-electron lasers. Instabilities in the RF launch phase can significantly reduce the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. The phase stability of the RF field is measured using the phase scan technique. Measurements were performed for different operating conditions at the Photo Injector Test facility at DESY, location Zeuthen (PITZ). Obtained stability measurement results will be presented and discussed.

MOPO037	Concept of Femtosecond Timing and Synchronization Scheme at ELBE	laser, controls, status, pick-up	565
	M. Kuntzsch, A. Büchner, M. Gensch, A. Jochmann, T. Kirschke, U. Lehnert, F. Röser HZDR, Dresden, Germany M.K. Bock, M. Bousonville, M. Felber, T. Lamb, H. Schlarb, S. Schulz DESY, Hamburg, Germany
	The Radiation Source ELBE at Helmholtz-Zentrum Dresden-Rossendorf is undergoing an extension to offer capacity for various applications. The extension includes the setup of a THz-beamline with a dedicated laboratory and a beamline for electron-beam - high-power laser interaction. The current synchronization scheme offers stability on the picoseconds level. For pump-probe experiments using optical lasers, the desired synchronization between the pump and the probe pulse should be on the femtosecond scale. In the future there will be an optical synchronization system with a pulsed fiber laser as an optical reference. The laser pulses will be distributed over stabilized fiber links to the remote stations. It is planned to install EOM-based beam arrival time monitors (BAMs) in order to monitor the bunch jitter and to establish a beam-based feedback to reduce the jitter. Besides that, the timing system has to be revised to generate triggers for experiments with low repetition rate, two electron guns (thermionic DC, superconducting RF) and several lasers. The Poster will show the possible layout of the future Timing and Synchronization System at ELBE.

MOPO042	Photonic Crystal Fibre Laser for Electron Beam Emittance Measurement*	laser, emittance, diagnostics, extraction	577
	L. Corner, L.J. Nevay, R. Walczak Oxford University, Physics Department, Oxford, Oxon, United Kingdom
	We discuss the recent progress in the development of a high repetition rate, high energy fibre laser for intratrain laser-wire scans of transverse electron beam sizes. A commercial fibre laser (1uJ, 6.49MHz) is amplified in rod type photonic crystal fibre using a burst mode format, which has the advantage of allowing us to exploit very high transient gain while reducing the heat load deposited in the amplifier. The amplified pulses are over 180uJ spaced at 154ns, suitable for intratrain scanning at the ATF2. The spatial beam quality is excellent (M2 = 1.07), indicating that it will be possible to focus the laser to a spot size of ~ λ, enabling us to reach high intensities. The amplified pulse duration is 200ps, which can be compressed to less than the electron bunch length to increase the laser-wire signal to noise ratio. The performance of the laser system is analysed with respect to the demands of the laser-wire experiment.

MOPO043	Applications of Lasers to Accelerator Physics at SSRL	laser, gun, cathode, photon	580
	D.L. Robinson Cal Poly, San Luis Obispo, California, USA W.J. Corbett SLAC, Menlo Park, California, USA
	Recent advances in accelerator physics and SR research have generated the need for high-power lasers in the SPEAR3 accelerator complex. On the injector side, two lasers are being used to test different photocathode materials and to provide photo-assisted emission from the standard dispenser cathode RF gun. For the storage ring, both a TiSa oscillator and a fiber laser locked to the RF master oscillator have been used to characterize short-pulse electron bunches in cross-correlation experiments. These lasers are also used in SR experiments for pump-probe characterization of materials. In this paper we review the laser-based systems, preliminary results and outlook for the future.

MOPS001	Electron-cloud Pinch Dynamics in Presence of Lattice Magnet Fields	proton, cyclotron, quadrupole, simulation	586
	G. Franchetti GSI, Darmstadt, Germany F. Zimmermann CERN, Geneva, Switzerland
	The pinch of the electron cloud due to a passing proton bunch was extensively studied in a field free region and in a dipolar magnetic field. For the latter study, a strong field approximation helped to formulate the equations of motion and to understand the complex electron pinch dynamics, which exhibited some similarities with the field-free situation. Here we extend the analysis to the case of electron pinch in quadrupoles and in sextupoles. We discuss the limits of validity for the strong field approximation and we evaluate the relative magnitude of the peak tune shift along the bunch expected for the different fields.

MOPS011	Impact of Low Transition Energy Optics to the Electron Cloud Instability of LHC Beams in the SPS	optics, simulation, synchrotron, emittance	616
	H. Bartosik, E. Benedetto, K.S.B. Li, Y. Papaphilippou, G. Rumolo CERN, Geneva, Switzerland
	One of the main limitations for high intensity multi-bunch LHC proton beams in the SPS is imposed by electron cloud instabilities. A new optics of the SPS with lower transition energy was implemented and successfully tested in machine studies. The significant increase of the slippage factor that it provides at injection energy results in the expected increase of the single bunch instability thresholds. In this paper, the impact of this new optics on the electron cloud instability threshold is estimated by using numerical simulations, taking into account the change of the optics functions and the faster synchrotron motion due to the reduced transition energy.

MOPS024	Bunch Dynamics through Accelerator Column	space-charge, TRIUMF, gun, cathode	649
	R.A. Baartman TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	Funding: TRIUMF research is supported by the National Research Council of Canada. The differential equations for the bunched beam envelope through an axially symmetric DC accelerator are derived. In the case of no space charge, a particle's total energy is conserved, so the longitudinal evolution is simple: particles of same energy are a fixed time increment apart and this implies in first order that their separation is proportional to their speed. However, with space charge, the longitudinal force depends upon the bunch length, so we need equations that track this parameter. The full 6-dimensional and relativistically correct envelope equations are derived.

MOPS029	Experiments with a Fast Chopper System for Intense Ion Beams	ion, space-charge, simulation, high-voltage	664
	H. Dinter, M. Droba, M. Lotz, O. Meusel, I. Müller, D. Noll, U. Ratzinger, K. Schulte, C. Wagner, C. Wiesner IAP, Frankfurt am Main, Germany
	Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ, an E×B chopper system is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50 ns at a repetition rate of 250 kHz for 120 keV, 200 mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6 kV and the resulting response was measured using a beam current transformer. A comparison between experiments and theoretical calculations as well as numerical simulations are presented.

MOPS033	Beam Dynamics Studies on the 100 MeV/100 kW Electron Linear Accelerator for NSC KIPT Neutron Source	linac, dipole, gun, simulation	673
	S. Pei, Y.L. Chi, M. Hou, W.B. Liu, G. Pei, S.H. Wang, Z.S. Zhou IHEP Beijing, Beijing, People's Republic of China N. Aizatsky, I.M. Karnaukhov, V.A. Kushnir, V. Mitrochenco, A.Y. Zelinsky NSC/KIPT, Kharkov, Ukraine
	We designed one 100MeV/100kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the base of subcritical assembly. Beam dynamics studies has been conducted to reach the design requirement (E=100MeV, P=100kW, dE/E<1% for 99% particles). In this paper, we will present the progress of the design and dynamics simulation results. For high intensity and long beam pulse linear accelerators, BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced at the downstream of the 1st accelerating section; the unwanted particles will be collimated there.

MOPS034	Progress on Space Charge Compensation Study in Low Energy High Intense H⁺ Beam*	emittance, injection, ion, space-charge	676
	P.N. Lu, Z.Y. Guo, S.X. Peng, Z.X. Yuan, J. Zhao PKU/IHIP, Beijing, People's Republic of China H.T. Ren Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China
	This article lays emphasis on the relationship between the Space Charge Compensation (SCC) and the beam quality in different conditions. Ar and Kr are used to compensate a 35keV/90mA H⁺ beam with the gas pressure from 3.7×10^-4 Pa to 6×10^-3 Pa. Experiments are conducted in different compensation states with three approaches. With an energy spectrometer, we have got the energy spectra of Extra Compensation Gas Ions (ECGI). By a beam profile meter, the beam profiles are obtained when the injection of compensation gas is gradually rising. In the meantime, the beam emittance is measured under different compensation conditions. After measurements of the above data, the potential and the rest charge distributions in the beam are calculated by analyzing the ECGI energy spectra and beam profiles. All experiments performed aimed to seek out the best circumstance for SCC dominated low energy high intensity ion beams.together to calculate the potential distribution are calculated by analyzing the energy spectra and beam profiles. All experiments performed aimed to seeking for the best circumstances in SCC dominated low energy high intensity ion beams.

MOPS035	Energy Spreads by Transient Beam Loading Effect in Pulsed RF Linac	gun, linac, bunching, beam-loading	679
	S.H. Kim, M.-H. Cho, G. Ha, H.R. Yang POSTECH, Pohang, Kyungbuk, Republic of Korea W. Namkung, S.J. Park PAL, Pohang, Kyungbuk, Republic of Korea J.-S. Oh NFRI, Daejon, Republic of Korea
	Funding: Work partly supported by KAPRA and POSTECH Physics BK21 Program RF linacs for high power beams are operated in the fully beam-loaded condition for the power efficiency. In this condition, temporal energy spreads are induced by the transient beam loading effect. Irradiation sources require the beam energy of less than 10 MeV to prevent undesirable neutron production. In order to maximize the beam power and maintain the beam energy in a safe value, we need to suppress the temporal energy spreads. In an L-band traveling-wave linac for irradiation sources, the high energy electrons are suppressed by the beam current modulation with the RF power modulation. As a result, the average beam energy and the corresponding beam power are improved by nearly 60% compared to the case without any modulations.

MOPS037	High Intensity Transient Beam Dynamic Study in Travelling Wave Electron Accelerators with Accounting of Beam Loading Effect	simulation, beam-loading, linac, space-charge	682
	S.M. Polozov, T.V. Bondarenko, E.S. Masunov, V.I. Rashchikov, A.V. Voronkov MEPhI, Moscow, Russia
	The beam loading effect is one of main problems limiting the beam current. The methods of beam dynamic simulation taking into account the beam loading effect were discussed previously. Simulation methods and the especial code version BEAMDULAD-BL was described in the paper. The beam loading effect was considered only for traveling wave linacs and for stationary beam only. Now it is important to study the beam dynamics of short current pulses, i.e. for transient process. We can consider only one beam bunch (or a packet of bunches) in a long external RF field pulse in stationary case. The beam radiation and wave fields can be calculated in the quasi-statically approximation. This approximation can not be used for transient mode. The methods of beam dynamics simulation will be discussed in this paper for transient mode. New code version BEAMDULAC-BLNS will be described. The simple test simulations will be carried out. A.V. Voronkov et al., "Beam Loading Effect of High Current Trawling Wave Accelerator Dynamic Study", Proc. of IPAC’10, Kyoto, Japan, TUPEA012, p. 1348 (2010).

MOPS040	Intra-Bunch Energy Spread of Electrons in Powerful RF Linacs for Nuclear Physics Research*	linac, target, HOM, simulation	691
	V.V. Mytrochenko, M.I. Ayzatskiy, V.A. Kushnir, A. Opanasenko, S.A. Perezhogin, V.L. Uvarov NSC/KIPT, Kharkov, Ukraine
	Funding: Ukrainian State program of fundamental and applied studies on the use of nuclear materials, nuclear and radiation technologies in the fields of economics (YaMRT project No. 826/35) There are some particles in RF electron linacs with energy that may be significantly different from that of particles within a core of the bunch. Loss of these particles at average beam power of tens of kilowatts can cause radiation and thermal problems. Filtration of such particles during the initial stage of acceleration, at energies below the threshold of photonuclear reactions, is important. The paper analyzes several ways to perform such type of filtration in the injector part of a powerful electron linac using a RF chopper or magnetic systems.

MOPS042	One-Dimensional Adiabatic Child-Langmuir Flow	simulation, emittance, gun, plasma	694
	C. Chen MIT, Cambridge, Massachusetts, USA R. Pakter, F.B. Rizzato IF-UFRGS, Porto Alegre, Brazil
	Funding: Research supported in part by US Department of Energy, Grant No. DE-FG02-95ER40919, CNPq, FAPERGS, INCTFCx of Brazil, and US Air Force Office of Scientific Research, Grant No. FA9550-09-1-0283. A theory is presented that describes steady-state one-dimensional Child-Langmuir flow at a self-consistent finite temperature distribution. In particular, warm-fluid equations and adiabatic equation of state are used to derive the self-consistent Poisson equation. The profiles of the charged-particle density, the velocity, the electrostatic potential, the pressure and the temperature are computed. Results are compared with self-consistent simulations.

MOPS048	Microbunching Instability Studies at SOLEIL	radiation, storage-ring, synchrotron, synchrotron-radiation	709
	C. Evain, J. Barros, J.B. Brubach, L. Cassinari, M.-E. Couprie, G. Creff, M. Labat, A. Loulergue, L. Manceron, R. Nagaoka, P. Roy, M.-A. Tordeux SOLEIL, Gif-sur-Yvette, France
	Microbunching instability arises in storage rings when the number of electrons in a bunch exceeds a threshold value. Its signature, i.e. a strong and irregular emission of Coherent Synchrotron Radiation (CSR) in the Terahertz (THz) domain, is studied at SOLEIL on the AILES infrared beamline, with the storage ring tuned in a low-alpha configuration (used to get shorter electron bunch). The comparison of this observed THz CSR with numerical simulations of the longitudinal electron bunch dynamics, permits to put in evidence that during the instability a modulation appears and drifts in the longitudinal profile of the electron bunch. The understanding of this instability is important as it limits some operation of the storage rings. Indeed the induced fluctuations prevent the use of THz on the far IR beamline at high current per bunch. And in normal alpha operation this instability may spoil the electron/laser interaction effects used to get femtosecond and/or coherent pulse in storage rings (with slicing, Coherent Harmonic Generation or EEHG schemes on storage ring).

MOPS049	Study of Ion-induced Instabilities and Transverse Feedback Performance at SOLEIL	ion, feedback, vacuum, simulation	712
	R. Nagaoka, L. Cassinari, M.D. Diop, J.-M. Filhol, M.-P. Level, A. Loulergue, P. Marchand, R. Sreedharan SOLEIL, Gif-sur-Yvette, France
	Experimental studies indicate that the SOLEIL storage ring at its maximum designed current of 500 mA is under a large influence of ions, potentially capable of inducing the so called fast beam-ion instability. To avoid it, the following three conditions have been empirically found effective: A reduced RF voltage, uniform filling and a large vertical chromaticity. While the choice of uniform filling appears contradictory to raising the ion instability threshold, it goes well with lowering of the RF voltage if outgassing due to beam-induced heating of the vacuum components is the primary source of ions. Additional difficulties associated are frequent occurrence of sudden beam blowups despite the presence of transverse feedback, which are large enough to trigger machine interlocks leading to complete beam losses. These blow ups may even take place horizontally inside in-vacuum insertion devices. The present paper reports on the results and findings obtained through experimental and simulation studies carried out on the collective beam dynamics and the transverse feedback performance, which are deeply interlinked, in order to clarify the mechanism of the encountered phenomena.

MOPS050	Electron Beam Dynamics in the 50 MeV ThomX Compact Storage Ring	emittance, scattering, photon, collective-effects	715
	C. Bruni, J. Haissinski LAL, Orsay, France A. Loulergue, R. Nagaoka SOLEIL, Gif-sur-Yvette, France
	ThomX is a high flux compact X-ray source based on Compton back scattering between a relativistic electron beam and an intense laser pulse. To increase the repetition rate, the electron beam is stored in a ring. The main drawback of such a scheme is the low energy of the electrons regarding collective effects and intrabeam scattering. These effects tend to enlarge or even disrupt the stored bunch and they limit its charge, especially in a system where damping plays a negligible role. Thus such collective effects reduce the maximum X-ray flux and it is important to investigate them to predict the performance of this type of X-ray source. In addition, the Compton back scattering acts on the electron beam by increasing its energy spread. This presentation will show firstly the impact of collective effects on the electron beam, essentially during the first turns when they are the most harmful. Then, the reduction of the X-ray flux due to Compton back scattering and intrabeam scattering will be investigated on a longer time scale.

MOPS053	Electron Cloud Effects in Coasting Heavy-ion Beams*	simulation, ion, accumulation, dipole	724
	F.B. Petrov, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany O. Boine-Frankenheim GSI, Darmstadt, Germany
	Funding: Work supported by BMBF under contract 06DA9022I. During slow extraction of intense ion beams electron clouds (EC) can accumulate in the circulating coasting beam and reduce the extraction efficiency. This is a concern for the existing SIS-18 heavy ion synchrotron at GSI and for the projected SIS-100 as part of the FAIR project. For medium energy heavy-ion beams the production of electrons from residual gas ionization is very effective. The electron density is limited due to Coulomb scattering by the beam ions. Above a threshold beam intensity the two-stream instability and the resulting coherent beam oscillations limit the electron density. Below this threshold the electron cloud can lead to observable deformations of the Schottky side-bands. To avoid EC build-up one can introduce a gap in the beam using barrier rf bucket. The reduction of the build-up efficiency caused by the gap is studied in details based on the solution of the Hill's equation for electrons. Finally we estimate the saturation level for the electron cloud density.

MOPS055	Observation of Intensity Dependent Single Bunch Effects at the Synchrotron Light Source PETRA III	impedance, emittance, synchrotron, single-bunch	730
	R. Wanzenberg, K. Balewski DESY, Hamburg, Germany
	At DESY the PETRA ring is operated as a synchrotron radiation facility with a very low emittance of 1 nm. Regular user operation has started in summer 2010. A summary of observations and measurements of intensity dependent single bunch effects is presented in this report. The longitudinal impedance of the ring is estimated from the measured bunch length versus beam intensity. The results are compared with predictions from the impedance model. Furthermore measurements of the single bunch intensity limit due to the transverse mode coupling instability (TMCI) are reported. The tune and phase shift around the ring has been measured as a function of the beam intensity. At PETRA III tune spectra have been observed with some characteristics which have been observed at other storage rings in connection with electron cloud effects. The present status of the observations of potential electron cloud effects is also discussed.

MOPS056	An Analytical Formula of the Electron Cloud Linear Map Coefficient in a Strong Dipole	dipole, vacuum, simulation, storage-ring	733
	T. Demma INFN/LNF, Frascati (Roma), Italy S. Petracca, A. Stabile U. Sannio, Benevento, Italy G. Rumolo CERN, Geneva, Switzerland
	Electron cloud effects have been indentified as one of the most serious bottleneck for reaching design performances in presently running and proposed future storage rings. The analysis of these effects is usually performed with very time consuming simulation codes. An alternative analytic approach, based on a cubic map model for the bunch-to-bunch evolution of the electron cloud density, could be useful to determine regions in parameters space compatible with safe machine operations. In this communication we derive a simple approximate formula relating the quadratic coefficient in the electron cloud density map to the parameters relevant for the electron cloud evolution in a strong vertical magnetic field. Results are compared with simulations with particular reference to the LHC dipoles.

MOPS057	Beam-beam Interaction under External Force Oscillation	luminosity, positron, simulation, kicker	736
	K. Ohmi KEK, Ibaraki, Japan
	Beam-ion interaction is strongly nonlinear. Response for external oscillation applied to beam shows characteristic feature. Simulations for external frequency scan becomes feasible for the recent computer power. We show the frequency response for beam-ion system in KEK-PF and recent low emittance rings.

MOPS069	Review of Beam Instabilities in the Presence of Electron Clouds in the LHC	emittance, injection, simulation, luminosity	760
	K.S.B. Li, G. Rumolo CERN, Geneva, Switzerland
	Recent observations at the LHC indicate the build-up of electron clouds when 50 ns spaced beams are injected into the machine at nominal intensity. These electron clouds are a source of coherent beam instabilities and incoherent emittance growth and limit the achievable luminosity. To better understand the influence of electron clouds on the beam dynamics, simulations have been carried out to study both the coherent and the incoherent effects on the beam. The simulations are performed with the HeadTail tracking code; the usage of new post-processing software allows determining not only the beam intensity thresholds in terms of the central electron cloud density but also the footprint of the beam in tune space. In this paper we review instability thresholds and tune footprints for beams with different emittances and interacting with an electron cloud in field-free or dipole regions.

MOPS083	Update on Electron Cloud Mitigation Studies at Cesr-TA*	wiggler, positron, resonance, photon	796
	J.R. Calvey, M.G. Billing, J.V. Conway, G. Dugan, S. Greenwald, Y. Li, X. Liu, J.A. Livezey, J. Makita, R.E. Meller, M.A. Palmer, S. Santos, R.M. Schwartz, J.P. Sikora, C.R. Strohman CLASSE, Ithaca, New York, USA S. Calatroni, G. Rumolo CERN, Geneva, Switzerland K. Kanazawa, Y. Suetsugu KEK, Ibaraki, Japan M.T.F. Pivi, L. Wang SLAC, Menlo Park, California, USA
	Funding: Work supported by the US National Science Foundation (PHY-0734867) and Department of Energy (DE-FC02-08ER41538) Over the course of the past three years, the Cornell Electron Storage Ring (CESR) has been reconfigured to serve as a test facility for next generation particle accelerators. A significant part of this program has been the installation of several diagnostic devices to measure and quantify the electron cloud effect, a potential limiting factor in these machines. In particular, more than 30 Retarding Field Analyzers (RFAs) have been installed in CESR. These devices measure the local electron cloud density and energy distribution, and can be used to evaluate the efficacy of different cloud mitigation techniques. This paper will provide an overview of RFA results obtained at CesrTA over the past year, including measurements taken as function of bunch spacing and wiggler magnetic field. Understanding these results provides a great deal of insight into the behavior of the electron cloud.

MOPS084	Status of Electron Cloud Dynamics Measurements at CESRTA*	dipole, betatron, damping, feedback	799
	M.G. Billing, G. Dugan, M.J. Forster, D.L. Kreinick, R.E. Meller, M.A. Palmer, G. Ramirez, M.C. Rendina, N.T. Rider, J.P. Sikora, K.G. Sonnad, H.A. Williams CLASSE, Ithaca, New York, USA J.Y. Chu CMU, Pittsburgh, Pennsylvania, USA J.W. Flanagan KEK, Ibaraki, Japan R. Holtzapple, M. Randazzo CalPoly, San Luis Obispo, California, USA
	Funding: Supported by US National Science Foundation (PHY-0734867) & Dept. of Energy (DE-FC02-08ER41538) The study of electron cloud-related instabilities for the CESR-TA project permits the observation of the interaction of the electron cloud with the stored beam under a variety of accelerator conditions. These measurements are undertaken utilizing automatic and semi-automatic techniques for three basic observations: the measurement of tune shifts of individual bunches along a train, the detection of the coherent self-excited spectrum for each bunch within a train and the pulsed excitation of either the betatron dipole or head-tail mode for each individual bunch within the train, followed by the observation of the damping of its coherent motion. These techniques are employed to study the electron cloud-related interactions in a number of conditions, such as trains of bunches with low emittance and spaced by as little as 4 nsec between bunches. We report on the most recent observations and results.

MOPS088	Simulation of Electron Cloud Beam Dynamics for CesrTA	emittance, simulation, betatron, positron	808
	K.G. Sonnad, G. Dugan, M.A. Palmer, G. Ramirez, H.A. Williams CLASSE, Ithaca, New York, USA K.R. Butler Cornell University, Ithaca, New York, USA M.T.F. Pivi SLAC, Menlo Park, California, USA
	This presentation provides a comprehensive set of results obtained using the simulation program CMAD. CMAD is being used for studying electron cloud induced beam dynamics issues for CesrTA, which is a test facility for studying physics associated with electron and positron damping rings. In particular, we take a closer look at electron cloud induced effects on positron beams, including head-tail motion, emittance growth and incoherent tune shifts for parameters specific to ongoing experimental studies at CesrTA. The correspondence between simulation and experimental results will also be discussed. Work supported by US Department of Energy grant number DE-FC02-08ER41538 and the National Science Foundation grant number PHY-0734867

MOPS091	Study of Electron Cloud for MEIC	simulation, emittance, luminosity, dipole	817
	S. Ahmed, J.D. Dolph, G.A. Krafft, T. Satogata, B.C. Yunn JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The Medium Energy Electron Ion Collider (MEIC) at Jefferson Lab has been envisioned as a future high energy particle accelerator beyond the 12 GeV upgrade of the existing Continuous Electron Beam Accelerator Facility (CEBAF). Synchrotron radiation from the closely spaced proton bunches in MEIC can generate photoelectrons inside the vacuum chamber and cause secondary emission due to multipacting in the presence of beam's electric field. This phenomenon can lead to fast build up of electron density, known as electron cloud effect – resulting into beam instability coupled to multi-bunches in addition to a single bunch. For MEIC, the estimated threshold value of the electron-cloud density is approximately 5 x 10¹² m-3. In this paper, we would like to report the self-consistent simulation studies of electron cloud formation for MEIC. The code has been benchmarked against the published data of electron cloud effects observed in LHC. Our first simulations predict increase of electron clouds with the increase of repetition rate. The detailed simulations are under progress and will be reported.

MOPZ004	Studies for the PRISM FFAG Ring for the Next Generation Muon to Electron Conversion Experiment	injection, kicker, extraction, septum	826
	J. Pasternak STFC/RAL, Chilton, Didcot, Oxon, United Kingdom M. Aslaninejad, L.J. Jenner, A. Kurup, J. Pasternak, Y. Shi, Y. Uchida Imperial College of Science and Technology, Department of Physics, London, United Kingdom R.J. Barlow UMAN, Manchester, United Kingdom K.M. Hock, B.D. Muratori Cockcroft Institute, Warrington, Cheshire, United Kingdom D.J. Kelliher, S. Machida, C.R. Prior STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom Y. Kuno, A. Sato Osaka University, Osaka, Japan J.-B. Lagrange, Y. Mori KURRI, Osaka, Japan M. Lancaster UCL, London, United Kingdom C. Ohmori KEK, Tokai, Ibaraki, Japan T. Planche TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada S.L. Smith STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom H. Witte, T. Yokoi JAI, Oxford, United Kingdom
	High intensity and high quality muon beams are needed for the next generation lepton flavour violation experiments. Such beams can be produced by sending a short proton pulse to a pion production target, capturing the pions and performing RF phase rotation on the resulting muon beam in an FFAG ring. Such a solution was proposed for the PRISM project and this paper summarizes its current status. In particular the PRISM task force was created to address the accelerator and detector issues that need to be solved in order to realise the PRISM experiment. Alternative designs for the PRISM FFAG ring are discussed and their performance compared. The injection/extraction systems and matching to the solenoid channels upstream and downstream of the FFAG ring are presented. The future direction for the study will be outlined.

MOPZ037	Extension of the 3-spectrometer Beam Transport Line for the KAOS Spectrometer at MAMI and Recent Status of MAMI	target, dipole, beam-transport, status	880
	R.G. Heine, M. Dehn, K.-H. Kaiser, H.-J. Kreidel, U.L. Ludwig-Mertin IKP, Mainz, Germany
	Funding: Work supported by DFG (CRC443) and the German Federal State of Rhineland-Palatinate The institute for nuclear physics (KPH) at Mainz University is operating a 1.6 GeV c.w. microtron cascade (MAMI) for nuclear physics research. One of the vast experimental activities is electron scattering. A 3-spectrometer setup is used for cross-section measurements of hadron knock-out and meson production. The KAOS spectrometer magnet of GSI is installed there in parallel to detect particles from (e,e'K)reactions under small forward angles. So the primary electron beam has to transit the spectrometer and after this it has to hit the existing beam dump. Because of the existing experimental setup, this must be realised by deflecting the beam before the target that is rotated to be in line with the KAOS spectrometer's inlet. This paper will deal with the basic concept of a flexible beam transport line (BTL) magnet chicane for different KAOS forward angles, while keeping the forward beam direction for the 3-spectrometer setup untouched. A survey concept for assembly and adjustment of the BTL will be introduced, that is also useful for future adjustments of the target mount after target change. Results of the BTL commissioning and a general MAMI status will be presented as well.

TUYA01	Achievements and Lessons from the Tevatron	antiproton, collider, luminosity, proton	903
	V.D. Shiltsev Fermilab, Batavia, USA
	The Tevatron Run-2 will come to an end at the time of IPAC'11. This talk will concentrate on exploration of the accelerator physics issues that were dealt with in achieving the current (very high) level of performance in the Tevatron and will review achievements, challenges and lessons learned on the way.
	Slides TUYA01 [5.881 MB]

TUZA01	Commissioning and Initial Operation of FERMI@Elettra	FEL, laser, photon, undulator	918
	S. Di Mitri, E. Allaria, R. Appio, L. Badano, S. Bassanese, F. Bencivenga, A.O. Borga, M. Bossi, E. Busetto, C. Callegari, F. Capotondi, K. Casarin, D. Castronovo, P. Cinquegrana, D. Cocco, M. Cornacchia, P. Craievich, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, P. Delgiusto, A.A. Demidovich, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, S. Ferry, V. Feyer, L. Fröhlich, P. Furlan Radivo, G. Gaio, F. Gelmetti, L. Giannessi, R. Gobessi, R. Ivanov, E. Karantzoulis, M. Kiskinova, M. Lonza, A.A. Lutman, C. Masciovecchio, R.H. Menk, M.M. Milloch, M.M. Musardo, I. Nikolov, S. Noe, F. Parmigiani, L. Pavlovič, E. Pedersoli, G. Penco, M. Petronio, M. Predonzani, E. Principi, E. Quai, G. Quondam, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Spezzani, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Wang, M. Zaccaria, D. Zangrando ELETTRA, Basovizza, Italy M. Alagia, A. Kivimaki, M. Zangrando, M. de Simone IOM-CNR, Trieste, Italy L. Avaldi, P. Bolognesi, M. Coreno, P. O’Keeffe CNR - IMIP, Trieste, Italy M. Dal Forno DIEIT, Trieste, Italy G. De Ninno, S. Spampinati University of Nova Gorica, Nova Gorica, Slovenia M. Devetta, T. Mazza, P. Piseri Università degli Studi di Milano, Milano, Italy E. Ferrari Università degli Studi di Trieste, Trieste, Italy S. Stranges Università di Roma "La Sapienza", Roma, Italy
	Funding: Work was supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3. This article describes the design goals of FERMI@Elettra, reports on the goals achieved so far and shows how the facility development has been driven by the new research frontier of ultra-fast, extreme ultra-violet and soft X-ray science. The commissioning phases and first experience with user pilot experiments are presented and discussed.
	Slides TUZA01 [13.401 MB]

TUZA02	sFLASH - Present Status and Commissioning Results	undulator, laser, FEL, radiation	923
	V. Miltchev, S. Ackermann, A. Azima, J. Bödewadt, F. Curbis, M. Drescher, E. Hass, Th. Maltezopoulos, M. Mittenzwey, J. Rönsch-Schulenburg, J. Roßbach, R. Tarkeshian Uni HH, Hamburg, Germany H. Delsim-Hashemi, K. Honkavaara, T. Laarmann, H. Schlarb, S. Schreiber, M. Tischer DESY, Hamburg, Germany R. Ischebeck PSI, Villigen, Switzerland S. Khan DELTA, Dortmund, Germany
	The free-electron laser in Hamburg (FLASH) was previously being operated in the self-amplified spontaneous emission (SASE) mode, producing photons in the XUV wavelength range. Due to the start-up from noise the SASE-radiation consists of a number of uncorrelated modes, which results in a reduced coherence. One option to simultaneously improve both the coherence and the synchronisation between the FEL-pulse and an external laser is to operate FLASH as an amplifier of a seed produced using high harmonics generation (HHG). An experimental set-up - sFLASH, has been installed to test this concept for the wavelengths below 40 nm. The sFLASH installation took place during the planed FLASH shutdown in the winter of 2009/2010. The technical commissioning, which began in the spring of 2010, has been followed by seeded-FEL commissioning, FEL-characterisation and pilot experiments. In this contribution the present status and the sFLASH commissioning results will be discussed.
	Slides TUZA02 [4.125 MB]

TUODA03	The Status of the ALICE Accelerator R&D Facility at STFC Daresbury Laboratory	FEL, radiation, cavity, diagnostics	934
	F. Jackson, D. Angal-Kalinin, R. Bate, R.K. Buckley, S.R. Buckley, J.A. Clarke, P.A. Corlett, D.J. Dunning, J.-L. Fernández-Hernando, A.R. Goulden, S.F. Hill, D.J. Holder, S.P. Jamison, J.K. Jones, L.B. Jones, A. Kalinin, S. Leonard, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, A.J. Moss, B.D. Muratori, T.T. Ng, J.F. Orrett, S.M. Pattalwar, Y.M. Saveliev, D.J. Scott, B.J.A. Shepherd, A.D. Smith, R.J. Smith, S.L. Smith, N. Thompson, A.E. Wheelhouse, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom P. Harrison, G.M. Holder, A.L. Schofield, P. Weightman, R.L. Williams, A. Wolski The University of Liverpool, Liverpool, United Kingdom M.D. Roper STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom M. Surman STFC/DL/SRD, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Science and Technology Facilities Council The ALICE accelerator, the first energy recovery machine in Europe, has recently demonstrated lasing of an infra-red free electron laser (IR-FEL). The current status of the machine and recent developments are described. These include: lasing of the IR-FEL, a programme of powerful coherent terahertz radiation research, electro-optic diagnostic techniques, development of high precision timing and distribution system, implementation of digital low level RF control. ALICE also serves as an injector for the EMMA non-scaling FFAG machine.
	Slides TUODA03 [1.648 MB]

TUOAB02	Simultaneous Long and Short Bunch Operation in an Electron Storage Ring - a Hybrid Mode based on Nonlinear Momentum Compaction	storage-ring, synchrotron, octupole, photon	945
	M. Ries, J. Feikes, A. Jankowiak, P.O. Schmid, G. Wüstefeld HZB, Berlin, Germany
	The generation of short pulses in electron storage rings is driven by different user groups like time resolved x-ray spectroscopy users or users of coherent synchrotron radiation. The required optics and operation conditions to generate this short bunches are worsening the experimental conditions, e.g. strongly reducing the average photon flux, for the regular user. Therefore short bunch operation is usually limited to dedicated user shifts. By controlling higher orders of the momentum compaction factor by higher multipoles it is possible to introduce a hybrid mode and simultaneously supplying long and short bunches. The Metrology Light Source (MLS) has the means to control these higher orders, therefore it is an ideal machine to investiate the feasibility of such a hybrid mode. Tracking results and first measurements will be shown. D. Robin et al., Proc. of EPAC08, p. 2100-2102, Genoa, Italy (2008). ** J. Feikes et al., Phys. Rev. ST Accel. Beams 14, 030705 (2011).
	Slides TUOAB02 [7.817 MB]

TUYB01	First Results from the EMMA Experiment	acceleration, cavity, injection, septum	951
	S. Machida STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	Report on first commissioning results and operational experience with EMMA, the world's first nonscaling FFAG. In particular review the effect of resonance crossing, and the efficiency of serpentine acceleration.
	Slides TUYB01 [9.201 MB]

TUYB02	The Challenges of Ultra-low Emittance Damping Rings	emittance, damping, quadrupole, coupling	956
	D. L. Rubin CLASSE, Ithaca, New York, USA
	Funding: Work supported by the National Science Foundation and by the US Department of Energy under contract numbers PHY-0734867 and DE-FC02-08ER41538. In this paper we review the state of the art of the design of damping rings for linear colliders, as supported by the experimental data from ATF and CESR test damping rings. We consider implications of measurements of electron cloud dynamics and mitigation in a radiation dominated ring. The techniques developed for tuning for ultra-low emittance in these rings are summarized. Other dynamics manifested in the ultra-low emittance regime where collective effects are important are discussed.
	Slides TUYB02 [7.198 MB]

TUODB02	Extreme High Vacuum System of High Brightness Electron Source for ERL	gun, vacuum, ion, cathode	979
	M. Yamamoto, T. Honda, Y. Honda, T. Miyajima, Y. Saito, Y. Tanimoto, T. Uchiyama KEK, Ibaraki, Japan H. Akimichi, H. Yoshida AIST, Tsukuba, Japan H. Kurisu Yamaguchi University, Ube-Shi, Japan
	A compact test accelerator for Japan’s future light source based on energy recovery linac (ERL) is under construction in KEK, aiming to demonstrate key technologies such as a high-brightness photocathode DC-gun and superconducting RF cavities. A DC-gun using GaAs-type photocathode which has a negative electron affinity (NEA) surface is employed. The NEA surface plays an indispensable role to extract electrons from conduction band minimum into vacuum. It assures high quantum efficiency of the photocathode and very low intrinsic emittance of the extracted beam. However, the NEA surface is extremely delicate against residual gas in vacuum. In order to extract mA-level beam currents continuously for more than several tens of hours, the pressure should be lower than the order of ·10^-10 Pa to avid the backbombardment of positive ions produced by the collision of accelerated electrons with residual gas molecules in the beam path. Recent achievements in the development of a 500-kV photocathode DC-gun and in the fundamental studies of its extreme high vacuum system will be presented.
	Slides TUODB02 [1.606 MB]

TUPC001	Simulations of the Interaction Point for TeV-scale e⁺ e− Colliders	photon, simulation, collider, radiation	985
	J. Esberg Aarhus University, Aarhus, Denmark
	The design of a detector and post collisional line of a future linear collider calls for detailed knowledge of the beam-beam dynamics at the interaction point. We here describe the implementation and results of new simulation tools in the program GUINEA-PIG. The subjects are direct trident production relevant in the deep quantum-regime, incoherent muon generation, synchrotron radiation from secondary particles and depolarization effects. We choose beam parameters in the range relevant for CLIC and comment on the implications for the design of such a machine.

TUPC009	The Recent JINR Advances in Technology Development on Linear Accelerators	laser, radiation, FEL, cryomodule	1006
	G. Shirkov, N. Balalykin, A. Dudarev, E. Syresin, G.V. Trubnikov, Yu.A. Yulian JINR, Dubna, Moscow Region, Russia E. Khazanov IAP/RAS, Nizhny Novgorod, Russia
	JINR experts take part in a few ILC related projects including photo injector prototype, participation in design and construction of cryomodules, RND on design of a new version of superconducting niobium resonator, laser metrology, etc. Some new results of this activity as well as recent data of ILC siting investigations in the Dubna region are presented.

TUPC021	The CLIC Feasibility Demonstration in CTF3	linac, cavity, acceleration, ion	1042
	P.K. Skowroński, J. Barranco, S. Bettoni, B. Constance, R. Corsini, A.E. Dabrowski, M. Divall Csatari, S. Döbert, A. Dubrovskiy, O. Kononenko, M. Olvegård, T. Persson, A. Rabiller, F. Tecker CERN, Geneva, Switzerland E. Adli University of Oslo, Oslo, Norway W. Farabolini CEA/DSM/IRFU, France R.L. Lillestol NTNU, Trondheim, Norway T. Muranaka, A. Palaia, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden
	The objective of the CLIC Test Facility CTF3 is to demonstrate the feasibility issues of the CLIC two-beam technology: the efficient generation of a very high current drive beam, used as the power source to accelerate the main beam to multi-TeV energies with gradient over 100MeV/m, stable drive beam deceleration over long distances. Results on successful beam acceleration with over 100 MeV/m energy gain are shown. Measurements of drive beam deceleration over a chain of Power Extraction Structures are presented. The achieved RF power levels, the stability of the power production and of the deceleration are discussed. Finally, we overview the remaining issues to be shown until the end of 2011.

TUPC028	Background and Energy Deposition Studies for the CLIC Post-Collision Line*	photon, simulation, radiation, positron	1060
	R. Appleby, M.D. Salt UMAN, Manchester, United Kingdom L.C. Deacon, E. Gschwendtner CERN, Geneva, Switzerland
	The CLIC post-collision line is designed to transport the spent-beam products of collision to their respective dumps, with minimal losses and thus minimal background contributions. With nanometre spot-sizes at TeV energies, large beam-beam effects induce divergence and dispersion of the outgoing beams, with a large production cross-section of Beamstrahlung photons and subsequently coherent pairs. The post-collision line should provide sufficient divergence of the beam to avoid damage to the vacuum exit and dump entrance windows. In this study, the beam losses are investigated, with the production of secondary particles from the interaction with matter simulated. The particle flux leakage from absorbers and dumps is modelled to determine the total energy deposited on magnets of the post-collision line. Finally, both electromagnetic and hadronic backgrounds at the CLIC experiment are considered.

TUPC030	Recommendation for Mitigations of the Electron Cloud Instability in the ILC	vacuum, positron, emittance, quadrupole	1063
	M.T.F. Pivi, L. Wang SLAC, Menlo Park, California, USA L.E. Boon, K.C. Harkay ANL, Argonne, USA J.A. Crittenden, G. Dugan, M.A. Palmer CLASSE, Ithaca, New York, USA T. Demma, S. Guiducci INFN/LNF, Frascati (Roma), Italy M.A. Furman LBNL, Berkeley, California, USA K. Ohmi, K. Shibata, Y. Suetsugu, J. Urakawa KEK, Ibaraki, Japan C. Yin Vallgren Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
	Funding: Work supported by the Director, Office of Science, High Energy Physics, U.S. DOE under Contract No. DE-AC02-76SF00515. Electron cloud has been identified as one of the highest priority issues for the ILC Damping Rings (DR). A working group has evaluated the electron cloud effect and instability, and mitigation solutions for the electron cloud formation. Working group deliverables include recommendations for the baseline and alternate solutions for the electron cloud mitigation in various regions of the ILC Positron DR, which is presently assumed to be the 3.2km design. Detailed studies of a range of mitigation options including coatings, clearing electrodes, grooves and novel concepts, were carried out over the previous several years by nearly 50 researchers, and the results of the studies form the basis for the recommendation. The assessments of the benefits or risks associated with the various options were based on a systematic ranking scheme. The recommendations are the result of the working group discussions held at numerous meetings and during a dedicated workshop. The mitigation choices will be also presented in a more detailed report later in 2012. In addition, a number of items requiring further investigation were identified and studies will be carried out at CesrTA and other institutions.

TUPC031	Advanced Research Electron Accelerator Laboratory Based on Photocathode RF Gun	gun, emittance, laser, controls	1066
	B. Grigoryan, G.A. Amatuni, V.S. Avagyan, A. Grigoryan, M. Ivanyan, V.G. Khachatryan, E.M. Laziev, K. Manukyan, I.N. Margaryan, V. Sahakyan, A. Sargsyan, A. Tarloyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan CANDLE, Yerevan, Armenia T. Vardanyan YSU, Yerevan, Armenia
	The low energy sub-picosecond duration electron bunches with extremely small beam emittance have wide applications in advanced research of new accelerator concepts, radiation physics, time-resolved pulse radiolysis and electron diffraction. The conceptual design and experimental program of the Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun are presented. The AREAL design implies single and multibunch operation modes with variable beam energy of 5-20 MeV and 10-100 pC bunch charge. The design is based on 3 GHz 1.6 cells RF gun followed by S-Band accelerating linac.

TUPC032	Beam Phase-Space Study for AREAL RF Photogun Linac	gun, emittance, space-charge, linac	1069
	B. Grigoryan, G.A. Amatuni, I.N. Margaryan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan CANDLE, Yerevan, Armenia
	In order to produce high brightness electron beams with sub-picosecond bunch duration, the creation of Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun is under consideration. For several experimental setup purposes the linac will operate in single and multibunch modes with final beam energy 5-20 MeV and the bunch charge 10 100 pC. The study of beam phase space evolution along the linac is performed to optimize the beam main characteristics: emittance, bunch length and energy spread. The dependence of longitudinal and transverse distribution of electrons in photocathode region on RF cavity performances is analyzed.

TUPC033	Verifying the Single Bunch Capability of the New Injector at ELSA*	linac, gun, single-bunch, pick-up	1072
	S. Mey, O. Boldt, W. Hillert, N. Hofmann, F. Klarner, D. Krönung, A. Roth, M. Schedler ELSA, Bonn, Germany S. Aderhold DESY, Hamburg, Germany
	Funding: Funded by the DFG within the SFB / TR 16 and the Helmholtz Alliance HA 10¹ "Physics at the Terascale". In order to enhance the operating capabilities of the Bonn University Accelerator Facility, ELSA, a new injector is currently under commissioning. One of its main purpose is to allow a single pulse mode. The injector produces a single electron bunch with 1.5 A pulse current. Design and optimization of the injector have been performed with EGUN, PARMELA and numerical simulations based on the numerical integration of the paraxial equation. A 1 ns long pulse is produced by a thermionic electron source with 90 kV anode - cathode voltage, then compressed and pre-accelerated by a subsequent 500 MHz RF cavity and a four-cell travelling wave buncher. Finally, the bunch will be accelerated to 20 MeV by the main LINAC section. Measurements have been conducted concerning the resulting pulse length and pulse charge to confirm the predictions made by simulations and to investigate the efficiency of the injector system.

TUPC034	Design Studies on 100 MeV/100 kW Electron Linac for NSC KIPT Neutron Source on the Base of Subcritical Assembly Driven by Linac	linac, emittance, gun, target	1075
	Y.L. Chi, J. Cao, X.W. Dai, C.D. Deng, M. Hou, X.C. Kong, R.L. Liu, W.B. Liu, C. Ma, G. Pei, H. Song, S.H. Wang, G. Xu, J. Zhao, Z.S. Zhou IHEP Beijing, Beijing, People's Republic of China M.I. Ayzatskiy, I.M. Karnaukhov, V.A. Kushnir, V.V. Mytrochenko, A.Y. Zelinsky NSC/KIPT, Kharkov, Ukraine S. Pei IHEP Beijng, Beijing, People's Republic of China
	In NSC KIPT, Kharkov, Ukraine, a neutron source on the base of subcritical assembly driven by 100 MeV/100 kW electron linear accelerator is under design and development. To provide neutron flux value of about 1013 neutron/s the electron linear accelerator with 100 MeV beam and average beam power of 100 kW will be used. Construction and manufacture of the linear accelerator of such high beam intensity with low emittance and beam losses is a challenging task. In the report the project of the electron linear accelerator of the required beam energy and intensity is described. The accelerator structure and main technical solutions are presented. To overcome the BBU effect of this high average beam current, several effective measures are adopt, such as using constant gradient structure to spread the HOMs frequencies different cells, larger inner radius and shorter section length make the higher group velocity and optimize the structure geometry to keep the shunt impedance as good as possible. After the beam bunching system, a chicane is followed to chopper the beam to avoid the beam lost in the higher energy part.

TUPC036	S-band ps Pulse Photoinjector for THz Radiation Source	coupling, electromagnetic-fields, gun, acceleration	1078
	S.M. Polozov, T.V. Bondarenko MEPhI, Moscow, Russia
	S-band photoinjectors with ps pulse are becoming promising as e-guns for high-intensity sub-mm wavelength pulse source. Development of accelerating system for photoinjector with ps bunch is reported. The main aim is to develop a model of accelerating structure that provide top accelerating fields in respect to high electric strength and low RF power uses. The accelerating structures consisting of 1.6 cell of disk-loaded waveguide (DLW), 3 cells and 2 half-cells of DLW, 7 cels and 2 half-cells of DLW and accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW are studying. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics, electric field distribution for all models were acquired. Accelerating structure consisting of 1.6 cells will operate in pi mode of standing wave, all other structures operate in pi/2 mode traveling wave. Accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW has most suitable electrodynamics characteristics and field distribution for sub-mm pulse source according to simulation results.

TUPC038	A Low Energy Thermionic RF Gun Linac for Ultrashort Electron Beam	linac, gun, bunching, klystron	1081
	J.-Y. Hwang, J.H. Chen, W.K. Lau, A.P. Lee, T.H. Wu NSRRC, Hsinchu, Taiwan N.Y. Huang NTHU, Hsinchu, Taiwan
	A low energy test linac is being constructed at NSRRC for technological development of high brightness electron injector. It is a 29 MeV S-band linac that equipped with a high gradient thermionic cathode rf gun for generation of ultrashort relativistic electron beam by velocity bunching in the rf linac section located at downstream. High quality GHz-repetition-rate electron pulses of about 30 pC in bunch charge, pulse duration as short as 100 fsec can be produced from this test facility. It can be used as the driver for future light source experiments such as ultrafast head-on inverse Compton scattering (ICS) X-ray source and intense coherent THz free electron lasers.

TUPC039	Proposals for Electron Beam Transportation Channel to Provide Homogeneous Beam Density Distribution at a Target Surface	target, neutron, quadrupole, beam-losses	1084
	A.Y. Zelinsky, I.M. Karnaukhov NSC/KIPT, Kharkov, Ukraine W.B. Liu IHEP Beijing, Beijing, People's Republic of China
	NSC KIPT neutron source will use 64x64 mm rectangular tungsten or uranium target. To generate maximum neutron flux, prevent overheating of the target and reduce thermal stress one should provide homogeneous electron beam distribution at the target surface. In the facility transportation channel three different possibilities of electron beam density redistribution along the target surface can be realized. It can be the fast beam scanning with two dimensional scanning magnets; the method of uniform beam distribution formation with linear focusing elements (dipole and quadrupole magnets) and nonlinear focusing elements (octupole magnets), when final required rectangular beam shape with homogeneous beam density is formed at target; and combined method, when one forms the small rectangular beam with homogeneous beam density distribution and scan it over the target surface with scanning magnets. In the report the all tree methods are considered and discussed considering the layout of the NSC KIPT transportation channel. Calculation results show that the proposed transportation channel lattice can provide uniform beam of rectangular shape with sizes 64x64 mm without target overheating.

TUPC040	Modified Lattice of the Compton X-ray Source NESTOR	lattice, storage-ring, sextupole, focusing	1087
	A.Y. Zelinsky, P. Gladkikh, A.A. Kalamayko, I.M. Karnaukhov, A. Mytsykov, A.A. Shcherbakov NSC/KIPT, Kharkov, Ukraine
	NESTOR is Compton X-ray source that is under commissioning in NSC KIPT. One of the main parts of the facility is the middle energy storage ring (40-225 MeV). The storage ring has comprehensive lattice to provide low emittance, low beam size in the interaction point and big value of the energy acceptance. One of the NESTOR storage ring lattice feature is use of bending magnets of 0.5 m radius with combined focusing function. It leads to increasing of 3D magnetic field effects on electron beam dynamics. After NESTOR magnetic element manufacturing characteristics of element magnetic fields were measured and the effect of the real magnetic field distribution on beam dynamics was calculated. As a result, to provide project X-ray source characteristics the parameters of NESTOR storage ring lattice should be modified. The second reason for the lattice modification was the desire to increase the interaction point straight section length. The results of the beam dynamics simulation after lattice modification and optimization show that the storage ring will provide all project electron beam parameters. The results of the electron beam simulations are presented in the paper.

TUPC041	Self-consistent Time-dependent Quasi-3D Model of Multipactor in Dielectric-loaded Accelerating Structures	space-charge, vacuum, multipactoring, plasma	1090
	O.V. Sinitsyn, T.M. Antonsen, G.S. Nusinovich UMD, College Park, Maryland, USA
	Funding: This work is supported by the Office of High Energy Physics of the US Department of Energy. Multipactor (MP) manifests itself as a rapid growth of the number of secondary electrons emitted from a solid surface in the presence of the RF field under vacuum conditions. The secondary electrons appear as the result of surface impacts of energetic primary electrons accelerated by the RF field. MP occurs in various microwave and RF systems and usually severely degrades their performance. Therefore, theoretical and experimental studies of MP are of great interest to researchers working in related areas of physics and engineering. In this paper we study MP in dielectric-loaded accelerating (DLA) structures. We started our work with the development of a self-consistent time-dependent 2D model of MP in such structures. To benchmark that model, we compared its results with available experimental data. The comparison showed good agreement between theory and experiment for DLA structures of larger diameter, however for structures of smaller diameter a significant discrepancy was observed. Therefore, we decided to develop a new quasi-3D model of MP that would allow us to take into account the effects ignored in our 2D studies. Results of our 3D analysis are presented in this paper. O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., Phys. Plasmas, 16, 073102 (2009). ** O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., AIP Conf. Proc., 1299, 302 (2010).

TUPC042	First Beam to FACET	linac, positron, controls, vacuum	1093
	R.A. Erickson, C.I. Clarke, W.S. Colocho, F.-J. Decker, M.J. Hogan, S. Kalsi, N. Lipkowitz, J. Nelson, N. Phinney, P. Schuh, J. Sheppard, H. Smith, T.J. Smith, M. Stanek, J.L. Turner, J. Warren, S.P. Weathersby, U. Wienands, W. Wittmer, M. Woodley, G. Yocky SLAC, Menlo Park, California, USA
	Funding: This work was supported by the Department of Energy contract DE-AC02-76SF00515. The SLAC 3km linear electron accelerator has been reconfigured to provide a beam of electrons to the new FACET facility while simultaneously providing an electron beam to the Linac Coherent Light Source (LCLS). FACET is a new experimental facility constructed in the linac tunnel that can transport, compress, and focus electron bunches to support a variety of accelerator R&D experiments. In this paper, we describe our first experiences with the operation of the linac for this new facility.

TUPC043	SEM Field Emission Probe Surface Science Study	cathode, vacuum, gun, laser	1096
	L. Laurent, R.E. Kirby, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This work is supported by Department of Energy Contract No. DE-AC03- 76SF00515. After decades of rf breakdown research, a common acknowledgement among researchers is that a better understanding of what is happening on the surface at a microscopic level needs to be the impetus for future studies. We are designing and fabricating an electron microscope-based high-electric-field current-emission probe to study topographic material features which will enable us to better understand and further advance the technology of high-brightness photocathode rf guns and enable the study of high gradient phenomena. The SEM field emission probe will provide an important diagnostic tool allowing cathodes and high gradient surfaces to be evaluated before and after testing and will help identify and understand the relationship between high field emission locations and vacuum breakdown, non-uniform emission, surface cracking, hotspots, etc. The preliminary results and 2012 goals will be presented.

TUPC045	Recirculating Electron Linacs (REL) for LHeC and eRHIC	linac, lattice, dipole, proton	1099
	D. Trbojevic, J. Beebe-Wang, Y. Hao, D. Kayran, V. Litvinenko, V. Ptitsyn, N. Tsoupas BNL, Upton, Long Island, New York, USA
	Funding: Work performed under a Contract Number DE-AC02-98CH10886 with the auspices of the US Department of Energy. We present a design of a CW Electron Recovery Linacs (ERL) for future electron hadron colliders eRHIC and LHeC. In eRHIC, a six-pass ERL would be installed in the existing tunnel of the present Relativistic Heavy Ion Collider (RHIC). The 5-30 GeV polarized electrons will collide with RHIC’s 50-250 (325) GeV polarized protons or 20-100 (130) GeV/u heavy ions. In LHeC a 3-pass 60 GeV CW ERL will produce polarized electrons for collisions with 7 TeV protons. After collision, electron beam energy is recovered and electrons are dumped at low energy. Two superconducting linacs are located in the two straight sections in both ERLs. The multiple arcs are made of Flexible Momentum Compaction lattice (FMC) allowing adjustable momentum compaction for electrons with different energies. The multiple arcs, placed above each other, are matched to the two linac’s straight sections with splitters and combiners.

TUPC055	Strongly Space Charge Dominated Beam Transport at 50 keV	solenoid, beam-transport, simulation, space-charge	1123
	D. Heiliger, W. Hillert, B. Neff ELSA, Bonn, Germany
	Funding: supported by DFG (SFB/TR16) A pulsed (100 nC in 1 us), low energetic beam of polarized electrons is routinely provided by an inverted source of polarized electrons at ELSA. The beam transport to the linear accelerator is strongly space charge dominated due to the beam energy of 50 keV. Thus, the actual beam current has an impact on the beam dynamics, and the optics of the transfer line to the linear accelerator must be optimized with respect to the chosen beam intensity. Numerical simulations of the beam transport demonstrate that an intensity upgrade from 100 mA to 200 mA is feasible. In order to successfully adjust the focussing strength of the magnets according to the final results of the simulation, dedicated beam diagnostics like wire scanners suitable for extreme-high vacuum applications are required.

TUPC057	Femtosecond Photoinjector and Relativistic Electron Microscopy	gun, emittance, laser, cathode	1126
	J. Yang, K. Kan, Y. Murooka, N. Naruse, K. Tanimura, Y. Yoshida ISIR, Osaka, Japan J. Urakawa KEK, Ibaraki, Japan
	A new rf gun driven by a femtosecond laser has been developed successfully for the relativistic electron diffraction in Osaka University for the study of ultrafast dynamics of intricate molecular and atomic processes in materials. The beam dynamics of femtosecond electron bunch in the rf gun were investigated to achieve a low-emittance and low-energy-spread; i.e. 0.1 mm-mrad and 10^-4. A time-resolved relativistic electron microscopy is being developed to reveal the hidden dynamics on the femtosecond and nanometer scales. The same demonstrations of the MeV electron diffraction/imaging measurements were reported.

TUPC058	Design of a Chirping Cell Attached RF Gun for Ultrashort Electron Generation	gun, cavity, laser, radiation	1129
	K. Sakaue, K. Tamai, M. Washio RISE, Tokyo, Japan J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 We have been developing an S-band photocathode rf electron gun at Waseda university. Our rf-gun cavity was firstly designed by BNL and then, modified by our group. In this paper, we will introduce a newly designed rf-gun cavity with energy chirping cell. To generate an energy chirped electron bunch, we attached extra-cell for 1.6cell rf-gun cavity. Cavity design was done by Superfish and particle tracing by PARMELA. By optimizing the chirping cell, we observed linear chirped electron bunch. The front electron have lower energy than rear. Then transporting about 2m, the bunch can be compressed down to 200fsec electron bunch with the charge of 160pC. This ultrashort bunch will be able to use for generating CSR THz radiation, pumping some material to be studied by pulse radiolysis method, and so on. In this conference, the design of chirping cell attached rf-gun, the results of tracing simulation and plan of manufacturing will be presented.

TUPC059	Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun	laser, beam-loading, cavity, gun	1132
	Y. Yokoyama, T. Aoki, K. Sakaue, T. Suzuki, M. Washio, T. Yamamoto RISE, Tokyo, Japan H. Hayano, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program. At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans.

TUPC060	A Multi-mode RF Photocathode Gun	gun, cathode, cavity, injection	1135
	S.V. Kuzikov, A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia J.L. Hirshfield Yale University, Physics Department, New Haven, CT, USA Y. Jiang Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA V. Vogel DESY, Hamburg, Germany
	A photocathode injection gun based on standard emittance compensating techniques and driven by several (N ≥ 2) harmonically related RF sources is considered. Multi-harmonic excitation can provide high-quality flatness in time of the field at the cathode when a bunch is being injected. This allows one to obtain ≥1 nC, 20-40 ps electron bunches with preservation of low emittance. Another advantage is a reduction of Ohmic losses and the required input RF power (for a given cathode field). Preliminary calculations show that input power in a three-mode cavity (0.65 GHz, 1.3 GHz, 2.6 GHz) is nearly half the power needed to feed a single mode with the same cathode field. A further appealing property is the predicted increase of breakdown threshold due to a reduction of surface exposure time to high fields in a symmetric cavity, and due to the so-called anode-cathode effect in a longitudinally asymmetric cavity. These properties may help one to reach bunch energies as high as 3-5 MeV after the first half cell.

TUPC062	Electron Beam Energy Measurement at the Australian Synchrotron Storage Ring	storage-ring, synchrotron, resonance, scattering	1138
	M.J. Boland ASCo, Clayton, Victoria, Australia H. Panopoulos, R.P. Rassool, K.P. Wootton The University of Melbourne, Melbourne, Australia
	The technique of resonant spin depolarization was used to precisely measure the electron beam energy in the storage ring at the Australian Synchrotron. A detector and data acquisition system dedicated to the measurement were developed. Using the system, the long term energy stability of the storage ring was monitored and a mechanical realignment of the ring was clearly seen in the energy data. Details of the parameters used to optimize the measurement are also discussed.

TUPC069	Bunch Length Measurements from the Incoherent Synchrotron Radiation Fluctuation at SOLEIL	radiation, undulator, optics, photon	1159
	M.-A. Tordeux, F. Dohou, M. Labat, O. Marcouillé SOLEIL, Gif-sur-Yvette, France
	Bunch length measurements can be made by analysing the pulse to pulse intensity fluctuation of the incoherent synchrotron radiation as it has been reported elsewhere. Such a method has been tested at SOLEIL for picosecond bunch durations, at several wavelengths and bandwidths in the visible range, using an avalanche photodiode. Thanks to the low-alpha optics the lengths of 10 μA bunches as short as 3 ps have been measured in good agreement with the streak camera results. We first used the radiation from a bending magnet, and then from a HU640 undulator that enhances the photon flux. Moreover, taking advantage of using the radiation from an undulator, we show that the method can still be used when the number of spikes emitted by the electron bunch is reduced to a few hundreds. This could be of interest for bunch length measurements of X-ray SASE FELs. Furthermore, we intend to use a single crystal diamond detector in order to perform these measurements in the X-ray range. F. Sannibale et al., "Absolute bunch length measurements by incoherent radiation fluctuation analysis", PRST AB 12, 032801 (2009).

TUPC072	Accurate Electron Beam Size Measurement at the Metrology Light Source	photon, radiation, polarization, storage-ring	1165
	R. Klein, G. Brandt, R. Thornagel PTB, Berlin, Germany J. Feikes, M. Ries, G. Wüstefeld HZB, Berlin, Germany
	For the operation of the Metrology Light Source (MLS), the dedicated electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB), as the national primary radiation source standard from the near infrared to the vacuum ultraviolet spectral region, all storage ring parameters which are relevant for the calculation of the radiant intensity by the Schwinger equation have to be known absolutely with small uncertainties. For the measurement of the effective vertical electron beam size a Bragg polarimeter, operating at a photon energy of 1103 eV, has been designed and put into operation. This system also serves as a detection system for the image of the electron beam through a set of narrow slits. The results obtained with the new device are compared to those measured by an optical beam imaging system. R. Klein et al., Phys. Rev. ST-AB 11, 110701 (2008). ** C. Koschitzki et al., Proc. IPAC10, 894-896 (2010).

TUPC074	A New Counting Silicon Strip Detector System for Precise Compton Polarimetry	polarization, photon, laser, scattering	1171
	R. Zimmermann, W. Hillert, J.C. Wittschen ELSA, Bonn, Germany
	Funding: Supported by the German Research Foundation within the SFB/TR16 A Compton polarimeter is currently being installed at the Electron Stretcher Facility ELSA to monitor the degree of polarization of the stored electron beam. For this purpose, circularly polarized light that is emitted by a laser and backscattered off the beam has to be detected. Above all, as a result of ELSA's beam energies, it is necessary to measure the shift of the center of the photon spatial distribution which is obtained when the polarization of the laser is switched from left-hand to right-hand circular polarization with an accuracy of a few microns. In order to meet the required specifications, a new counting silicon strip detector system has been developed in cooperation with the SiLab/ATLAS group of the Physics Institute of the University of Bonn. In this contribution, the design of the system will be presented and first results will be shown.

TUPC076	Realization of a High Bandwidth Bunch Arrival-time Monitor with Cone-shaped Pickup Electrodes for FLASH and XFEL	pick-up, laser, coupling, free-electron-laser	1177
	A. Angelovski, M. Hansli, R. Jakoby, A. Kuhl, A. Penirschke, S. Schnepp TU Darmstadt, Darmstadt, Germany M. Bousonville, H. Schlarb DESY, Hamburg, Germany T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Funded by the Federal Ministry of Education and Research (BMBF): 05K10RDA In the Free Electron Laser in Hamburg (FLASH) an electro-optical system is used as a Bunch Arrival time Monitor (BAM). The time-of-arrival resolution is proportional to the steepness of the beam pick-up signal at the first zero-crossing. Future experiments will be conducted using significantly lower bunch charges resulting in a reduced signal steepness. This requires BAM pickup electrodes with increased bandwidth as introduced in . This paper presents the implementation and measurement results of a high bandwidth cone-shaped pickup capable of operating in the frequency range up to 40 GHz. The slope steepness at the zero crossing is investigated for a simplified equivalent circuit model. RF-measurements have been performed using a non-hermetic prototype of the BAM pickups for assessing the influence of manufacturing tolerances on the sensor performance. The measurements are compared to simulation results obtained by CST PARTICLE STUDIO®. F. Loehl et al., Proc. of DIPAC2007, WEPB15, p. 262 (2007). ** A. Angelovski et al., "Pickup design for a high resolution Bunch Arrival time Monitor for FLASH and XFEL", DIPAC2011.

TUPC079	Sensitivity and Tolerance Analysis of a New Bunch Arrival-time Monitor Pickup Design for FLASH and XFEL	pick-up, simulation, laser, free-electron-laser	1186
	A. Kuhl, A. Angelovski, R. Jakoby, A. Penirschke, S. Schnepp TU Darmstadt, Darmstadt, Germany M. Bousonville, H. Schlarb DESY, Hamburg, Germany T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Supported by the Graduate School of Computational Engineering at TU Darmstadt and the Federal Ministry of Education and Research (BMBF): 05K10RDA "Weiterentwickung eines Ankunftszeitmonitors" The Free Electron Laser in Hamburg (FLASH) is equipped with Bunch Arrival Time Monitors (BAM), which provide for a time resolution of less than 10 fs for bunch charges higher than 0.2 nC. Future experiments, however, will aim at generating FEL light pulses from a broad range of bunch charges down to 10 pC. In these circumstances the requirements on the time resolution will no longer be fulfilled, which demands for a larger bandwidth of the pickup system. A new cone-shaped pickup, which has a bandwidth greater than 40 GHz has been proposed. At high frequencies, small manufacturing tolerances might have great influence on the pickup signal. A sensitivity analysis of several manufacturing tolerances in the pickup design regarding their influence on the output signal was carried out (by means of CST PARTICLE STUDIO®). These results are utilized for setting limits to the manufacturing tolerances. M.K. Bock et al., IPAC2010, WEOCMH02, Kyoto, Japan, 2010. ** A. Kuhl et al., "Design eines hochauflösenden Ankunftszeitmonitor für FLASH", DPG Frühjahrstagung 2011, Karlsruhe, Germany.

TUPC081	Diagnostics of Femtosecond Low-charge Electron Bunches at REGAE	photon, diagnostics, laser, simulation	1192
	S. Bayesteh Uni HH, Hamburg, Germany H. Delsim-Hashemi DESY, Hamburg, Germany
	A new linac is constructed at DESY as the electron source fo "Relativistic Electron Gun for Atomic Exploration (REGAE)". REGAE is mainly established for a Femtosecond electron diffraction experiment presenting structural information on atomic transition states occurring in the sub-hundred femtosecond time-scale. REGAE comprises a photo-cathode gun followed by normal conducting 1.5 cell RF cavity to provide sub pico-Coulomb charge of 2 to 5 MeV energy with a coherent length in the range of 30nm. In order to produce and maintain such high quality electron bunches, sophisticated single-shot diagnostics is mandatory to monitor the properties. Diagnostics include emittance, energy, energy spread and bunch length measurement. In this paper the conceptual ideas and steps toward realization of these diagnostics are presented with a detailed focus on transverse diagnostics. As for photon source of transversal diagnostics, scintillators are studied. Simulation results show which material suits the best for REGAE parameters. Layout of a home-made intensified camera is presented. The method discussed in this paper would also be advantageous for low-charge Free Electron Lasers.

TUPC082	Beam Current Measurements at the TSR Heidelberg	ion, pick-up, acceleration, storage-ring	1195
	M. Grieser, S.T. Artikova, K. Blaum, F. Laux, J. Ullrich MPI-K, Heidelberg, Germany
	To conduct experiments using low energy ion beams at the TSR heavy ion storage ring, the beam deceleration process must be well understood. During deceleration of the beam the revolution frequency decreases, resulting in low current, which is difficult to measure with a common DC transformer. The number of particles in a bunch is determined by measuring the voltage signal in the time domain using a capacitive pick-up. If the ratio of bunch length and RF period does not change during the deceleration or acceleration, measuring the pick-up signal spectrum, where the signal is directly proportional to the number of particles in a bunch, is a more sensitive method. An alternative method is using a beam profile monitor (BPM) for determining the number of particles in the storage ring via ionization rate measurements of the residual gas. A summary of these different methods to determine the number of particles is presented.

TUPC083	Comparative Studies into 3D Beam Loss Simulations	simulation, photon, beam-losses, positron	1198
	M. Panniello MPI-K, Heidelberg, Germany C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: Work supported by the Helmholtz Association and GSI under contract VH-NG-328. A detailed understanding and monitoring of potential beam loss mechanisms is crucial for every particle accelerator. The main motivation in low energy facilities, such as the Ultra-low energy Storage Ring (USR) at the future Facility of Low energy Antiproton and Ion Research (FLAIR), comes from the very low number of particles available which in such machine ought to be conserved. In High Energy accelerators it is the concern about activation or even physical damage of machine parts which has to be taken into serious account. The CLIC Test Facility (CTF3) at CERN provides an ideal testing ground for studies into novel BLM systems and is well suited for benchmarking the results from numerical simulations in experiments. This contribution summarizes the three-dimensional beam loss pattern as found with the commonly used codes FLUKA and Géant4. The results from these codes are compared and analyzed in detail and used for the identification of optimum beam loss monitor locations.

TUPC084	Performance of the Scintillation Profile Monitor in the COSY Synchrotron	vacuum, synchrotron, proton, target	1201
	V. Kamerdzhiev, J. Dietrich, K. Reimers FZJ, Jülich, Germany
	Residual gas scintillation is used for measuring profile of the proton beam circulating in the COSY synchrotron. The problem of low rate of scintillation events detected by a multichannel photomultiplier is coped with by injecting small amounts of pure nitrogen into the SPM vacuum chamber. This leads to a temporary local pressure bump of no more than an order of magnitude. A commercially available piezo-electric dosing valve allows good control over the amplitude and duration of the pressure bump. Since the average pressure in the machine is hardly changed, the method is fully compatible with experiment operation. This approach offers a robust and inexpensive way to measure the beam profile. The design of the SPM is discussed. The latest measurement results and comparison to the ionization profile monitor data is presented.

TUPC086	A Setup for Single Shot Electro Optical Bunch Length Measurements at the ANKA Storage Ring	laser, storage-ring, synchrotron, radiation	1206
	N. Hiller, E. Huttel, A.-S. Müller, A. Plech KIT, Karlsruhe, Germany F. Müller, P. Peier, V. Schlott PSI, Villigen, Switzerland
	Funding: Supported by the Initiative and Networking Fund of the Helmholtz Association under VH-NG-320. Sponsored by the German Federal Ministry of Education and Research under contract number 05K10VKC Single shot electro optical bunch length measurements, in particular using spectral decoding, are foreseen for the ANKA storage ring. This will allow to resolve fast changes of bunch deformation and structure during the low alpha operation (2-15 ps rms bunch length). This technique uses a chirped laser pulse to probe the field induced birefringence in an electro optical crystal. The laser pulse is then analyzed in a single shot spectrometer. To obtain the birefringence modulation one can either use the near field of the electron bunch (placing the crystal close to the electron bunch in the UHV system of the storage ring), or the far field (coherent synchrotron radiation in the THz range at a THz-/IR-Beamline). The laser needs to supply: sufficient tunability of pulse length, a wide spectrum to allow for a sub-ps resolution. Additionally it must provide a mode-locked operation synchronized to the bunch revolution clock. For this purpose, a mode locked Ytterbium fibre laser system which operates at 10³⁰ nm has been developed at the Paul-Scherrer Institute in Switzerland. We give an overview over the experimental set up in the ANKA storage ring and the status of the project.

TUPC087	Filling Pattern Measurements at the ANKA Storage Ring	photon, storage-ring, single-bunch, synchrotron	1209
	B. Kehrer, N. Hiller, A. Hofmann, E. Huttel, V. Judin, M. Klein, S. Marsching, A.-S. Müller, N.J. Smale KIT, Karlsruhe, Germany
	For many accelerator physics studies, e.g. the investigation of coherent synchrotron radiation (CSR), a precise knowledge of the quantitative filling pattern (i.e. the number of electrons per bunch) is essential. This can be achieved by either using a linear detector (analog recording) or by employing the method of time-correlated single photon counting (TCSPC). At the ANKA storage ring both methods are in use. The analogue detection is based on the signal from a stripline or annular electrode, the TCSPC uses a Single Photon Avalanche Diode (SPAD). In this paper, we describe the experimental set-ups and present results of a comparison of the two techniques for single as well as for multi bunch filling patterns.

TUPC088	An Ionization Profile Monitor for the Determination of the FLASH and PITZ Beam Parameters	photon, vacuum, diagnostics, ion	1212
	J. Mießner, H.-J. Grabosch, M. Markert, R. Sternberger DESY Zeuthen, Zeuthen, Germany A. Hofmann KIT, Karlsruhe, Germany K.I. Tiedtke DESY, Hamburg, Germany
	To operate FLASH (Free-electron LASer at Hamburg) successfully, accurate measurements of the photon beam parameters, like position and profile, are essential. The development of a specific Ionization Profile Monitor (IPM) is one contribution to the photon beam diagnostics, and currently one horizontal and one vertical oriented IPM are installed at FLASH. The working principle of the IPM is based on the detection of ions generated by interactions of the photon beam with the residual gas, which is always present in the beam line. An essential advantage of this method is that the beam is not influenced by the IPM, so it is possible to analyze the beam parameters without beam destruction. Moreover, the monitor is able to determine the relative position and the spatial profile of the beam with the precision of a few um. In this poster, the design and first measurements with the IPM taken at FLASH are presented. A good measuring accuracy of the IPM is obtained. Moreover, first results of measurements at PITZ (PhotoInjector Testfacility at Zeuthen) are given for one vertical oriented IPM with a up to 25 MeV electron beam.

TUPC091	Operational Results of the Diamond-based Halo Monitor during Commissioning of SPring-8 XFEL (SACLA)	undulator, laser, wakefield, scattering	1218
	H. Aoyagi JASRI/SPring-8, Hyogo-ken, Japan Y. Asano, H. Kitamura, T. Tanaka RIKEN/SPring-8, Hyogo, Japan
	Funding: This work is partly supported by Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (c) 21604017. Measurement of electron beam halo is very important issue for X-ray free electron laser and synchrotron radiation facilities, because the beam halo may cause radiation damage of undulator magnets. Furthermore, it may cause degradation in quality of electron beam, and radio activation of beam ducts and components. In order to prevent these situations, a diamond-based halo monitor (HM) has been developed for the SPring-8 Angstrom Compact free electron LAser (SACLA). We have achieved excellent detection limit of 0.3 fC/pulse for single-shot measurement, which corresponds to the ratio of 10^-6 to the beam core. The commissioning of the HM, which was installed at the upstream of 90m undulator, has been carried out, and it has been figured out that the intensity of the beam halo can be measured very nicely since secondary electrons and bremsstrahlung that are emitted in the accelerator components have not been observed. We also describe systematic profile measurements of the beam halo and operational results of the HM during the commissioning of SACLA.

TUPC093	CSR Bunch Length Monitor for XFEL/SPring-8 - SACLA	radiation, FEL, synchrotron, synchrotron-radiation	1224
	C. Kondo, S. Matsubara, T. Matsumoto JASRI/SPring-8, Hyogo-ken, Japan S.I. Inoue, H. Maesaka, Y. Otake RIKEN Spring-8 Harima, Hyogo, Japan
	SPring-8 Angstrom Compact Free Electron Laser (SACLA) is now under commissioning operation, aimed at the generation of a sub-angstrom free electron laser (FEL). In order to ensure the stable FEL generation, non-distractive bunch length monitors utilizing coherent synchrotron radiation (CSR) are installed. The monitors are located at the downstream of individual bunch compressor (BC1-BC3), and they measure the radiation emitted at the individual last magnets of the chicanes. At the magnets, beams with bunch lengths form 10 fs to 1000 fs generate the CSRs with a spectrum ranging the almost whole infrared region (0.03 - 3 THz). The CSRs are detected by a Schottky diode at the BC1, or pyroelectric detectors and a simple organic lens optical system at BC2 and 3. The bunch length monitor systems are used for bunch length feedback control to obtain the stable lasing by changing the rf parameter of acceleration cavities before the BCs. A preliminary system for the above mentioned system was tested at the SCSS test accelerator, and it showed sufficient performance to measure bunch length up to 300 fs. In this report, we describe the design and the results of the first operation.

TUPC094	Development of High-speed Differential Current-transformer Monitor	bunching, gun, monitoring, status	1227
	S. Matsubara, H. Ego, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan A. Higashiya, S.I. Inoue, Y. Otake RIKEN/SPring-8, Hyogo, Japan H. Maesaka RIKEN Spring-8 Harima, Hyogo, Japan
	The XFEL, which was named SACLA, was constructed in the SPring-8 site. In the SACLA, the bunch length of an electron beam is compressed from 1 ns to 30 fs, and the beam charge is decreased to obtain a genuine electron beam from 1nC to 0.3 nC for lasing. A new current-transformer (CT) monitor, which should measure the charge of the electron beam and make bunch length observation in velocity bunching process, was developed with two advantageous properties. One is differential output signal which suppresses common-mode noise from the thyratron of a klystron modulator by a factor of ten. Another property is high-speed signal output which provides a possibility to measure the bunch length and the time-of-flight (TOF) at the injector part of the SACLA. The output signal has 200 ps rise-time and a pulse width of 400 ps (FWHM) for an impulse beam. We successfully observed the bunch length between 1 ns and 400 ps around a 238 MHz buncher cavity. Moreover, we measured the TOF between two CTs with a few picoseconds resolution for a low-energy beam around 1 MeV. Thus, the new CT performance was confirmed to be sufficient for the SACLA.

TUPC101	Generation of Multimode Quasi-monochromatic Terahertz	linac, radiation, gun, cathode	1248
	K. Kan, T. Kondoh, K. Norizawa, A. Ogata, J. Yang, Y. Yoshida ISIR, Osaka, Japan
	Generation of quasi-monochromatic terahertz (THz) using multimode Coherent Cherenkov Radiation (CCR) on the order of 0.1 THz was investigated. CCR was generated by a hollow dielectric tube covered by a metal and an electron bunch from a photocathode radio-frequency (RF) gun linac. The intensity and frequency of CCR were measured directly by a Michelson interferometer and a bolometer. The frequency spectra measured by the interferometer indicated sharp peaks close to frequencies of 0.09 THz and 0.14 THz, which corresponded to TM03 and TM04 modes, respectively, according to theoretical calculation for a tube with inner and outer radii of 5 mm and 7 mm. The maximum gain of TM03 mode due to the tube length was obtained as 1.5 dB/cm. The other higher modes, e. g. 0.36 THz (TM09) and 0.40 THz (TM010), were also observed from a 150 mm long tube at a bunch charge of 15 pC, which decreased space charge effect and the bunch length. Finally, a new method for bunch diagnostic based on multimode CCR was proposed. The bunch length was estimated to be 0.45 ps at a bunch charge of 5 pC with the intensity ratio of TM03 to TM09 mode.

TUPC109	Electron Bunch Slice Emittance Measurement with the Space Charge Effects*	solenoid, emittance, space-charge, simulation	1272
	C. Li, Y.-C. Du, W.-H. Huang, C.-X. Tang, L.X. Yan TUB, Beijing, People's Republic of China
	Funding: supported by the National Natural Science Foundation of China (Grant Nos. 10735050, 10805031, 10875070 and 10925523), and the National Basic Research Program of China (Grant No. 2007CB815102). Since slice transverse emittance of the electron beam is critical to a high-gain short-wavelength FEL, its characterization is very important. For space charge dominated electron beam, conventional emittance measurement techniques, such as solenoid scanning and quadruple scanning, without considering space charge forces lead to large errors of emittance evaluations. This essay introduces a modified solenoid-scan method of slice emittance measurement for space charge dominated beam, and simulations show that the new method brings the emittance evaluations much closer to actual values.

TUPC124	Laser Wire Emittance Measurement Line at CLIC*	laser, emittance, photon, collider	1308
	H. Garcia, Yu.A. Kubyshin UPC, Barcelona, Spain T. Aumeyr, G.A. Blair JAI, Egham, Surrey, United Kingdom D. Schulte, F. Stulle CERN, Geneva, Switzerland
	A precise measurement of the transverse beam size and beam emittances upstream of the final focus is essential for ensuring the full luminosity at future linear colliders. A scheme for the emittance measurements at the RTML line of the CLIC using laser-wire beam profile monitors is described. A lattice of the measurement line is discussed and results of simulations of statistical and machine-related errors and of their impact on the accuracy of the emittance reconstruction are given. Modes of operation of the laser wire system and its main characteristics are discussed.

TUPC129	A Beam Position System for Hadrontherapy Facilities	photon, controls, vacuum, proton	1323
	A. Faus-Golfe, C. Belver-Aguilar, C. Blanch Gutierrez, J.J. García-Garrigós IFIC, Valencia, Spain E. Benveniste, M. Haguenauer, P. Poilleux LLR, Palaiseau, France
	Funding: MICINN-FPA:AIC10-D-000518 Essential parts of the needed instrumentation for the beam control in the Hadrontherapy accelerators are the Beam Position Monitors (BPM). The measurement of the beam position in Hadronterapy accelerators become more important at the secondary transport lines towards the patient room where this parameter must be completely determined. The BPM described in this paper is a new type of BPM based on four scintillating fibers coupled to four photodiodes to detect the light produced by the fibers when intercepting the beam. We present here the study of the different photodiodes able to read the light emitted by the scintillating fiber, the tests performed in order to find the most suitable photodiode to measure the beam position from the variations in the beam current, the mechanical design and the corresponding acquisition electronics.

TUPC132	Imaging of the MAX III Electron Beam Profile Using Visible Synchrotron Radiation	emittance, diagnostics, synchrotron, lattice	1332
	A. Hansson, Å. Andersson, E.J. Wallén MAX-lab, Lund, Sweden
	The recently assembled MAX III diagnostic beam line utilizes the bending magnet synchrotron radiation (SR) in the visible to ultraviolet range to form images of the transverse electron beam profile. Computer simulations model the generation and propagation of the SR through the beam line, taking into account effects such as diffraction, the longitudinally distributed source point and the curvature of the electron orbit. Using the diagnostic beam line, the electron beam size and the emittance in the MAX III synchrotron light source has been determined.

TUPC133	Instrumentation for the 12 GHz Stand-alone Test-stand to Test CLIC Acceleration Structures	vacuum, laser, diagnostics, ion	1335
	M. Jacewicz, R.J.M.Y. Ruber, V.G. Ziemann Uppsala University, Uppsala, Sweden J.W. Kovermann CERN, Geneva, Switzerland
	Vacuum breakdown is one of the primary limitations in the design and construction of high energy accelerators operating with warm accelerating structures (ACS) such as CLIC linear collider because the mechanisms that cause the breakdown are still a mystery. The ongoing experimental work is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the observed discharges. The CLIC collaboration is preparing a dedicated 12 GHz test-stand to observe the characteristics of the RF discharges and their eroding effects on the ACS. The instrumentation for the test-stand must be versatile and allow for the conditioning of the ACS with measurements of the breakdown rates at different power levels as well as detection of the dark current and light emission directly relevant to breakdown physics. For that purpose we are developing 2 novel instruments. A pepper-pot chamber with an external magnetic spectrometer for measurement of the spatial and energy distributions of the electrons emitted from the ACS and an optical laser system for probing the ACS to observe the effect of a discharge on the transmitted light.

TUPC135	Beam Loss Monitors Comparison at the CERN Proton Synchrotron	beam-losses, injection, radiation, proton	1341
	S.S. Gilardoni, S. Aumon, E. Effinger, J. Gil Flores CERN, Geneva, Switzerland U. Wienands SLAC, Menlo Park, California, USA
	CERN is planning the renovation and upgrade of the beam loss detection system for the Proton Synchrotron (PS). Improved performance in speed–to be able to monitor beam loss on a bunch-by-bunch basis–and in long-term stability–to reduce or avoid the need for periodic calibration–are aimed for. To select the most suitable technology, different detectors were benchmarked in the machine with respect to the same beam loss. The characteristics of the different detectors, the results of the measurement campaign and their suitability as future monitors for the PS are presented.

TUPC142	The Particle Identification System for the MICE Beamline Characterization	emittance, beam-losses, laser, solenoid	1356
	M. Bonesini INFN MIB, MILANO, Italy Y. Karadzhov DPNC, Genève, Switzerland
	The International Muon Ionization Cooling Experiment (MICE) will carry out a systematic investigation of a ionization cooling section of a muon beam, for the future Neutrino Factory and the future Muon Collider. As the emittance measurement will be done on a particle-by-particle basis, a sophisticated beam instrumentation is needed to measure both particle coordinates and timing vs RF in a harsh environment due to high particle rates, fringe magnetic fields and RF backgrounds. A PID system, based on three time-of-flight stations (with resolutions up to 50-60 ps), two Aerogel Cerenkov counters and a KLOE-like calorimeter (KL) has been constructed and has allowed the commissioning of the MICE muon beamline in 2010. It will be complemented in 2011 by an Electron Muon Ranger to determine the muon range at the downstream end of the cooling section. Detector performances, as obtained in the 2010 run, will be shown and the use of PD detectors for the beamline characterization, including a preliminary measure of emittance, fully illustrated.

TUPC144	Preliminary BPM Electrics Testing for the Taiwan Photon Source Project	injection, brilliance, controls, feedback	1362
	C.H. Kuo, J. Chen, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.-Y. Liao NSRRC, Hsinchu, Taiwan
	The preliminary BPM electrics are developing and testing for Taiwan Photon Source (TPS), is a 3 GeV synchrotron light source which being in construction at NSRRC. This new BPM electronics with integrated FPGA based hardware, and will be testing in the TLS (Taiwan Light Source) with real beam at first. The enhance functionality of current generation will be adopted in the TPS. The electronic prototype testing and relative property will be reported in this report.

TUPC151	Cherenkov Fibre Optic Beam Loss Monitor at ALICE	beam-losses, photon, laser, monitoring	1383
	A. Intermite The University of Liverpool, Liverpool, United Kingdom A. Intermite, M. Putignano, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The need for real-time monitoring of beam losses, including evaluation of their intensity and the localization of their exact position, together with the possibility to overcome the limitations due to the reduced space for the diagnostics, makes optical fibres (using the Cherenkov Effect) one of the most suitable and explored candidate for beam loss monitoring. In this contribution, we report on an optical fibre beam loss monitor based on large numerical aperture pure silicon fibres and silicon photomultipliers, tested at ALICE, Daresbury Laboratories, UK. The original design of the sensor has the advantage to combine the functions of a real time detector and a transmission line. It also allows reading the signals independently and determining the time and position of the losses without the use of an external trigger.

TUPC152	Comparative Study of Performance of Silicon Photomultipliers for Use in Cherenkov Fibre Optic Beam Loss Monitors	photon, beam-losses, monitoring, lattice	1386
	A. Intermite The University of Liverpool, Liverpool, United Kingdom A. Intermite, M. Putignano, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Silicon Photomultipliers (SiPMs) are semiconductor photo-sensitive devices built from a matrix of Single Photon Avalanche Diodes (SPADs) on a common silicon substrate, working in the limited Geiger mode and with a common readout. The fast counting ability, high timing resolution, immunity to magnetic field up to 15 T, low power consumption and relative small temperature dependence together with the small dimensions make SiPMs excellent candidates as commercially available solid state detectors, and a promising alternative to traditional photomultiplier tubes for single photon detection. Nevertheless, SiPMs do suffer from erroneous counting due to noise effects that can deteriorate their performances. These effects are, in general, heavily dependent on manufacturing quality. In this contribution, results are reported of the characterization of different models of SiPMs in terms of noise spectra and response to light, and a procedure for determining quality manufacturing parameters is described.

TUPC154	Commissioning of the Detection System for a Supersonic Gas-jets Based Transverse Beam Profile Monitor	ion, extraction, simulation, storage-ring	1392
	M. Putignano, D. Borrows, A. Intermite The University of Liverpool, Liverpool, United Kingdom M. Putignano, M.R.F. Siggel-King, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: Work supported by STFC, the EU under GA-ITN-215080, the Helmholtz Association and GSI under VH-NG-328. We present the commissioning results of the Micro-Channel-Plate (MCP) based, ion extraction and detection system currently in use for an experimental test stand aimed at demonstrating the operation of a least-interceptive transverse beam profile monitor based on a planar supersonic gas-jet. This monitoring design features least-interceptive operation under excellent vacuum conditions and provides fast acquisition of a fully bi-dimensional transverse profile. It bears application for ultra-low energy particle beams at future storage rings, but also for e.g. linacs at high currents and light source injectors. For instance, the Ultra-low energy Storage Ring (USR), part of the Facility for Antiproton and Ion Research (FAIR) in Germany will store antiprotons at energies of 20-300 keV. In this contribution, we report numerical simulations and experimental results obtained by calibration of the detection system with a low energy electron beam to demonstrate a 1 mm imaging resolution only limited by recoiling ion drift.

TUPC158	Micron-scale Laser-wire at the ATF-II at KEK Commissioning and Results	laser, optics, photon, diagnostics	1401
	L.J. Nevay, G.A. Blair, S.T. Boogert, L. Corner, L.C. Deacon, V. Karataev, R. Walczak JAI, Oxford, United Kingdom A.S. Aryshev, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	We present the first results from the commissioning of the upgraded laser-wire experiment at the Accelerator Test Facility 2 (ATF2) at KEK. A new laser transport line and beam diagnostics were used to collide 150 mJ, 167 ps long laser pulses with 1.28 GeV, 30 ps long electron bunches to measure the vertical transverse size. Additionally, a new detector was installed with a reduced area for lower background. Initial scans showing a convoluted beam size of 19.2 ± 0.2 microns were used to tune the electron beam optics and reduce this down to 8.1 ± 0.1 microns. Laser pulse energy and charge dependency were investigated showing a linear relationship in both with a minimum laser energy of 20 mJ required for observable signal with this laser and setup.

TUPC159	Energy Measurements with Resonant Spin Depolarisation at Diamond	storage-ring, feedback, resonance, quadrupole	1404
	I.P.S. Martin, M. Apollonio, R.T. Fielder, G. Rehm Diamond, Oxfordshire, United Kingdom R. Bartolini JAI, Oxford, United Kingdom
	A precise knowledge of the electron beam energy is critical for the accurate determination of many light source parameters, such as momentum compaction factor, natural chromaticity, energy stability and undulator spectra. In common with other facilities, a method of energy measurement based on resonant spin depolarisation has been developed at Diamond. In this paper we report on progress towards storage ring characterisation using this method, as well as describing the diagnostics developments that have enabled these measurements to be made.

TUPC162	Thin Foil-based Secondary Emission Monitor for Low Intensity, Low Energy Beam Profile Measurements	antiproton, proton, ion, target	1413
	J. Harasimowicz, J.-L. Fernández-Hernando, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom L. Cosentino, P. Finocchiaro, A. Pappalardo INFN/LNS, Catania, Italy J. Harasimowicz The University of Liverpool, Liverpool, United Kingdom
	Funding: Work supported by STFC, the EU under GA-ITN-215080, the Helmholtz Association and GSI under VH-NG-328. A secondary emission monitor (SEM) was developed for beam profile measurements at the Ultra-low energy Storage Ring (USR) that will be installed at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) in Darmstadt, Germany. The detector consists of an Aluminium foil on negative potential, a grounded mesh placed in front of the foil, a chevron type microchannel plate (MCP), a phosphor screen and a camera connected to a PC. Simulations of the optimized design together with experimental results with keV protons are presented in this contribution. In addition, the usability of the detector for low energy antiproton beam profile measurements is discussed.

Paper

Title

Other Keywords

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MOYBA01

Present Status of the ILC Project and Developments

cavity, linac, linear-collider, collider

16

M.C. Ross
Fermilab, Batavia, USA
N.J. Walker
DESY, Hamburg, Germany
A. Yamamoto
KEK, Ibaraki, Japan

Funding: FNAL is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The Technical Design of the ILC Project will be finished in late 2012. The Technical Design Report will include a description of the updated design, with a cost estimate and a project plan, and the results of R & D done in support of the ILC. Results from directed ILC R & D are used to reduce the cost and risk associated with the ILC design. We present a summary of key challenges and show how the global R & D effort has addressed them. The most important activity has been in pursuit of very high gradient superconducting RF linac technology. There has been excellent progress toward the goal of practical industrial production of niobium sheet-metal cavities with gradient performance in excess of 35 MV/m. In addition, three purpose-built beam test facilities have been constructed and used to study and demonstrate high current linac performance, electron-cloud beam dynamics and precision beam control. The report also includes a summary of component design studies and conventional facilities cost optimization design studies.

Slides MOYBA01 [9.755 MB]

MOYCA01

Status Report on the Commissioning of the Japanese XFEL at SPring-8

laser, undulator, acceleration, FEL

21

H. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

The Japanese XFEL at SPring-8, which was named SACLA (Spring-8 Angstrom Compact free electron LAser), was completed in FY2010. After RF full-power aging for about four months the beam commissioning of SACLA has been started since 21 February 2011. About one month later, in 23 March a design beam energy of 8 GeV was achieved and a spontaneous undulator radiation of 0.8 Angstrom was observed at the beam-line optical hutch by closing XFEL undulator gaps down to 5 mm in full-width. The beam commissioning has proceeded smoothly and since the middle of April we have entered to a tuning phase towards SASE lasing, which is at least one month ahead of schedule. This talk will report the beam commissioning overview of SACLA including SASE XFEL performance, key tuning-processes and critical issues for achieving the lasing.

Slides MOYCA01 [37.840 MB]

MOOCA03

Updates to the International Linear Collider Damping Rings Baseline Design

lattice, damping, positron, cavity

32

S. Guiducci, M.E. Biagini
INFN/LNF, Frascati (Roma), Italy
G. Dugan, M.A. Palmer, D. L. Rubin
CLASSE, Ithaca, New York, USA
J. Gao, D. Wang
IHEP Beijing, Beijing, People's Republic of China
M.T.F. Pivi, Y. Sun
SLAC, Menlo Park, California, USA
J. Urakawa
KEK, Ibaraki, Japan

A new baseline design for the International Linear Collider (ILC) damping rings has been adopted which reduces the ring circumference to 3.2 km from 6.4 km. This design change is associated with a revised plan to operate the ILC with one half the beam current originally specified in the ILC Reference Design Report. We describe the new layout and lattice that has been developed for the shorter ring. In addition, we discuss features of the new design that will allow operation at a 10Hz repetition rate which is twice the rate specified for baseline operation. Finally, we examine the implications for restoring operation with the originally specified beam current while maintaining the smaller ring circumference.

Slides MOOCA03 [2.381 MB]

MOOCB02

Commissioning and Performance of the Beam Monitor System for XFEL/SPring-8 “SACLA”

cavity, undulator, bunching, FEL

47

Y. Otake, C. Kondo, H. Maesaka
RIKEN Spring-8 Harima, Hyogo, Japan
H. Ego, S. Matsubara, T. Matsumoto, T. Sakurai, H. Tomizawa, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan
S.I. Inoue
SES, Hyogo-pref., Japan

The construction of a beam monitor system for XFEL/SPring 8 “SACLA” was completed. The system was developed to realize a spatial resolution of less than 3 um to align a beam orbit for an undulator section with about 100 m long and a temporal resolution to measure bunch lengths from 1 ns to 30 fs to maintain a constant peak beam current conducting stable SASE lasing. The system principally comprises cavity type beam position monitors (BPM), current monitors (CT), screen monitors (SCM) and bunch length measurement instruments, such as an rf deflector and CSR detectors. Commissioning of SACLA started from March 2011, and the monitors performed sufficient roles to tune beams for the lasing. The achieved over-all performances of the system including DAQ are: the BPM have spatial resolution of 300 nm, the bunch length monitors observe bunch lengths from 1ns in an injector with velocity bunching to less than 30 fs after three-stage bunch compressors. The less than a 3 um spatial resolution of the SCM was also confirmed in practical beam operation. By these fulfilled performances, the stable lasing of SACLA will be achieved. This report describes commissioning, performance of the system.

Slides MOOCB02 [7.516 MB]

MOODB02

RF Modeling Plans for the European Spallation Source

cavity, HOM, beam-losses, linac

56

S. Molloy, M. Lindroos, S. Peggs
ESS, Lund, Sweden
R. Ainsworth
Royal Holloway, University of London, Surrey, United Kingdom
R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden

The European Spallation Source (ESS) will be the world's most powerful next generation neutron source. The ESS linac is designed to accelerate highly charged bunches of protons to a final energy of 2.5 GeV, with a design beam power of 5 MW, for collision with a target used to produce the high neutron flux. In order to achieve this several stages of RF acceleration are required, each using a different technology. The high beam current and power require a high degree of control of the accelerating RF, and the specification that no more than 1 W/m of losses will be experienced means that the excitation and decay of the HOMs must be very well understood. Experience at other high power machines also implies that an understanding of the generation and subsequent trajectories of any field-emitted electrons should be understood. Thermal detuning of the HOM couplers due to multipacting is a serious concern here. This paper will outline the RF modeling plans - including the construction of mathematical models, simulations of HOMs, and multipacting - during the current Accelerator Design Update phase, and will discuss several of the more important issues for ESS.

Slides MOODB02 [48.641 MB]

MOPC009

Design of a Pi/2 Mode S-Band Low Energy TW Electron Linear Accelerator

coupling, acceleration, linac, simulation

80

H. Shaker
IPM, Tehran, Iran
F. Ghasemi
sbu, Tehran, Iran
H. Shaker
CERN, Geneva, Switzerland

This design is related to a Pi/2 mode S-Band low energy TW electron linear accelerator which is in the construction stage. This project is supported by the school of particles and accelerators, institute for research in fundamental sciences (IPM), Tehran, Iran. This design consists of a buncher and an accelerating structure that are joined and two couplers for the input/output feedings. At each design stage, different methods (analytical or numerical) are used to confirm the results and also to have a better understanding.

MOPC018

Operation Status of C-band High Gradient Accelerator for XFEL/SPring-8 (SACLA)

accelerating-gradient, klystron, acceleration, target

104

T. Inagaki, C. Kondo, T. Ohshima, Y. Otake, T. Sakurai, K. Shirasawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Shintake
RIKEN Spring-8 Harima, Hyogo, Japan

XFEL project in SPring-8 have constructed a compact XFEL facility*. In order to shorten an accelerator length, a C-band (5712 MHz) accelerator was employed due to a higher accelerating gradient than that of an S-band accelerator. Since a C-band accelerating structure generates a gradient of higher than 35 MV/m, the total length of an 8 GeV accelerator fits within 400 m, including 64 C-band RF units, 4 S-band RF units, an injector and three bunch compressors. The accelerator components were carefully installed by September 2010. Then we have performed high power RF conditioning. After 500 hours of the conditioning, the accelerating gradient of each C-band structure was reached up to 35 MV/m without any particular problem. The RF breakdown rate is low enough for an accelerator operation. Since February 2011, we started the beam commissioning for XFEL. The C-band accelerator has accelerated the electron beam up to 8 GeV, with an accelerating gradient of 33-35 MV/m in average. The energy and the trajectory of the electron beam was stable, thanks to the stabilization of a klystron voltage of 350 kV within 0.01% by a high precision high voltage charger.
*The facility was recently named SACLA (SPring-8 Angstrom Compact free electron LAser).

MOPC020

Development of an S-band Multi-cell Accelerating Cavity for RF Gun and Booster Linac

gun, cavity, booster, linac

110

T. Aoki, K. Sakaue, M. Washio
RISE, Tokyo, Japan
A. Deshpande
SAMEER, Mumbai, India
M.K. Fukuda, N.K. Kudo, T. Takatomi, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported by JST Quantum Beam Program
We have been developing a photocathode rf gun. The rf gun with multi cell can produce a high energy electron beam, so it may be used for numerous applications such as medicine and industry. At Laser Undulator Compact X-ray source (LUCX), we have developed a compact X-ray source based on inverse Compton scattering. Using a multi cell rf gun will make possible for the X-ray source to use for such applications. S-band 3.5 cell rf electron gun which is 20 cm long can produce more than 10 MeV electron beam. According to the simulation, it is said that the emittance of 3.5 cell rf gun is as low as that of 1.6 cell rf gun. The electromagnetic design has been performed with the code SuperFish, and the particle tracing by Parmela. The new rf gun is already installed and produced a high quality electron beam with energy of more than 10 MeV. As a consequence of the substantial efforts of developing rf cavity, we decide to make a compact RF accelerating structure with more cell for achieving a smaller system. The measurement results of using the 3.5 cell rf gun, the design of 12 cell booster cavity, and current status of 12 cell cavity manufacturing will be presented at the conference.

MOPC022

Development of a Compact C-band Photocathode RF Gun

gun, cathode, injection, emittance

116

X.H. Liu, H. Chen, W.-H. Huang, H.J. Qian, C.-X. Tang, Z. Zhang
TUB, Beijing, People's Republic of China

Funding: This work is supported by National Natural Science Foundation of China and National Basic Research Program of China (973 Program).
A C-band photocathode RF gun for a compact electron diffraction facility is developed in Tsinghua University, which is designed to work at the frequency of 5.712GHz. This paper presents the physics and structure design of this C-band RF gun, and the comparison on beam dynamics of S-band and C-band photoinjector has been done. Some new structure design will be adopted in this gun, including the optimized cavity length and elliptical iris, which is helpful to achieve lower emittance and larger mode separation.

MOPC023

Design of a C-band 6 MeV Standing-wave Linear Accelerating Structure

coupling, bunching, impedance, simulation

119

J.H. Shao, H. Chen, Q.Z. Xing
TUB, Beijing, People's Republic of China

We design a C-band standing-wave biperiodic on-axis coupled linear accelerating structure for industrial and medical applications. It’s less than 300mm long; consists of 3 bunching cells and 9 normal cells. It can accelerate electrons to 6MeV and the pulsed beam current is 100mA. The RF power source is a 2.5MW magnetron. We implement 2D cells geometry optimization by SUPERFISH, beam dynamics study by PARMELA and full scale 3D calculations by MAFIA codes.

MOPC029

Development of Injector for Compact FEL Tera-hertz Source in CAEP

gun, FEL, booster, simulation

131

W. Bai, M. Li, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

This paper introducs the development of a injector for compact FEL tera-hertz source at Institute of Applied Electronics in China Academy of Engineering Physics (IAE/CAEP). The injector consist of a main accelerator for energy booster section and a multicavity thermionic-cathode rf gun with low back bombardment, with total length no more than one meter. Numerical simulation result shows that the back bombardment power is less for the thermionic-cathode rf gun of the injector and the main accelerator has a good performance, which can provide high quality electron beam with emittance about 10 pi mm mrad, energy about 7 MeV and energy spread about 1%. At present, the preliminary hot test experiment on the injector has been done. The test results indicate that the mainly tested parameters agree well with the theoretical design ones. The process of the preliminary hot test experiment on the injector is present in this paper.

MOPC034

Design of a 0.6-cell Cell Photocathode RF Gun for FED

gun, simulation, cathode, solenoid

145

Y.W. Parc, M.S. Chae, I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea

Final goal of this study is the development of single cell radio-frequency (RF) electron gun which is optimized to the femotosecond electron diffraction. This study will open new technology basis for the laboratory research in the femto-second (fs) chemistry at the university. RF electron gun will be fabricated with single cell which will reduce the cost and effort. We will also conduct a simulation study to find an optimized operation condition of the RF gun to provide the best electron beam to the femtosecond electron diffraction experimentalist. In this presentation, we will show the status of the RF gun development. The results with the simulation code PARMELA will be presented to find the optimal operation condition of the single cell RF gun for FED.

MOPC035

Design and Machine Features of 2.2-m C-band Accelerating Structure

cavity, accelerating-gradient, linac, vacuum

148

C.H. Yi, M.-H. Cho, S.H. Kim, H. Lee
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Namkung
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This work is partly supported by the MEST, Korea and POSTECH BK21 Program. And this work was supported by the Korea Student Aid Foundation (KOSAF) grant funded by the Korea government.
A compact linac system is designed using a longer accelerating column in a C-band linac. It reduces the total number of RF units for the given linac beam energy and results in the cost-effective use of RF powers. For the 10 GeV PAL-XFEL project, a C-band accelerating column of 2.2-m long is investigated, which is 22% longer than 1.8-m for the SACLA at SPring-8. The detailed RF and thermal characteristics are presented by an analytic model.

MOPC041

Cross-Field Multipactor Discharge in the X-Band Cylindrical Cavity

cavity, multipactoring, vacuum, radiation

166

S.V. Kuzikov, E.V. Ilyakov, I.S. Kulagin, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia
D. Lee
NSRRC, Hsinchu, Taiwan

The paper represents the experimental study of one-sided cross-field multipactor discharge in the copper cavity with the operating mode TM01 in external DC magnetic field. It was shown that discharge is very sensible to magnitudes of the external magnetic field and rf fields as well. At proper fields the multipactor discharge can be developed for 15 ns and the electron concentration can be comparable with critical one for the given rf frequency. As a result of discharging, the cavity changes its own resonant frequency and can play a role of a switch which can substitute full transmission by full reflection. Switching parameters could be controlled by DC magnetic field as well as by additional rf radiation at different frequency than operating frequency. The high rf absorption of multipactor discharge also can be used in electrically controlled powerful loads and attenuators.

MOPC050

Multipacting Analysis for the Superconducting RF Cavity HOM Couplers in ESS

cavity, simulation, HOM, superconducting-RF

190

S. Molloy
ESS, Lund, Sweden
R. Ainsworth
Royal Holloway, University of London, Surrey, United Kingdom
R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden

The European Spallation Source (ESS) linac will consist of three families superconducting RF cavities to accelerate protons to the required 5 MW for collision with the target. If it is determined that HOM damping is required to limit the effect of beam induced modes, it is quite likely that HOM couplers will be installed. Multipacting in these couplers is a concern as thermally induced detuning of the fundamental notch filter has limited the achievable gradient in other high power machines. It is therefore important to avoid potential multipacting conditions during the design phase. Presented here are simulations using the Track3P code developed at SLAC. Multipacting regions are highlighted, electron trajectories are shown, and suitability of the proposed HOM coupler design is discussed.

MOPC059

The Plane Wave Transformer Linac Development at NSRRC

linac, simulation, impedance, cavity

217

A. Sadeghipanah, J.-Y. Hwang, W.K. Lau
NSRRC, Hsinchu, Taiwan
T.H. Chang
NTHU, Hsinchu, Taiwan

A Plane-Wave-Transformer (PWT), standing wave linac operating at S-band frequency (2.9979 GHz) is being developed at NSRRC. This structure offers the advantages of high efficiency, compactness, fabrication simplicity and cost. The PWT prototype at NSRRC consists of three cells with two half-cells at the ends, separated by a set of four flat disks suspended and cooled by four water tubes inside a large cylindrical tank. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 2-D code SUPERFISH and 3-D code MAFIA. In this paper, we describe the principle properties of this structure, the electric parameters obtained from numerical simulations, and heat dissipation calculation. The mechanical design for prototype linac is also reported.

MOPC060

Bunching-frequency Multiplication for a THz Pulse-train Photoinjector

bunching, linac, laser, acceleration

220

Y.-C. Huang, F.H. Chao, C.H. Chen, K.Y. Huang
NTHU, Hsinchu, Taiwan

Funding: This work is supported by National Science Council under Contract NSC 99-2112-M-007 -013 -MY3.
A THz-pulse-train photoinjector* employs a THz-pulse-train laser as its driver laser to generate a beam with a bunching frequency in the THz range. However a laser frequency is on the order of a few hundred THz. It is not possible to generate a beam from the pulse-train photoinjector with a bunching frequency exceeding the laser’s carrier frequency. In view of the strong demand for a compact x-ray free-electron laser (FEL), it is highly desirable to multiply the bunching frequency of the beam from a pulse-train injector to the x-ray frequencies. We propose to chirp the energy of the THz electron pulse train in an accelerator and compress the whole beam in a magnet to increase the electron bunching frequency. Our study shows a compression ratio or a bunching-frequency multiplication factor of a few tens is achievable from a properly designed magnetic chicane compressor. The bunching factor, however, is unfortunately degraded due to the energy chirp, emittance growth, and wake-field generation. In the conference, we will show that a bunching factor of a few ppm in the bunch-frequency multiplied beam is sufficient to build up the FEL power from a 10-time length reduced undulator.
* Y. C. Huang, “Laser-beat-wave bunched beam for compact superradiance sources,” International Journal of Modern Physics B, Vol. 21 Issue 3/4, p277-286 (2007).

MOPC065

Ion Motion in the Vicinity of Microprotrusions in Accelerating Structures

ion, simulation, plasma, background

232

D.G. Kashyn, T.M. Antonsen, I. Haber, G.S. Nusinovich
UMD, College Park, Maryland, USA

Funding: This work is supported by Office of High Energy Physics of the U.S. Department of Energy.
It is known that newly fabricated accelerating structures have almost ideally smooth surface. However, ‘post mortem’ examination of these structures reveals that their surface can be significantly modified after high-gradient operation. This surface modification can be caused by the appearance of microscopic protrusions*. One of the factors leading to heating, melting and evaporation of these protrusions (factors resulting in the RF breakdown) is ion bombardment**. In our study we analyze ion motion in the vicinity of microprotrusions both analytically and numerically. First, we study the ion motion in the RF electric field magnified by the protrusion in the absence of electron field emitted current and show that most of the ions do not reach the structure surface. Then we add into consideration the interaction of ions with Fowler-Nordheim current emitted from the tip of protrusion (dark current). First, we develop a model describing this interaction and then we supplement it with numerical results using PIC code WARP***. We show that the ions move towards the area occupied by the dark current, but this does not increase the bombardment of micro-protrusions.
* R.B. Palmer,et al, Phys. Rev ST Accel. Beams 12, 031002 (2009).
** P. Wilson, AIP Conf. Proc., 877, Melville, New York, 2006, p. 27.
***J.-L. Vay, et al, Physics of Plasmas, 11, 2928 (2004).

MOPC067

X-Band Test Station at Lawrence Livermore National Laboratory

klystron, cathode, laser, brightness

235

R.A. Marsh, F. Albert, S.G. Anderson, C.P.J. Barty, G.K. Beer, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck
LLNL, Livermore, California, USA
C. Adolphsen, A.E. Candel, T.S. Chu, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou
SLAC, Menlo Park, California, USA

Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
An X-band multi-bunch test station is being built at LLNL to investigate the science and technology paths required to boost the current mono-energetic gamma-ray (MEGa-Ray) brightness by orders of magnitude. The test station will consist of a 5.5 cell X-band RF photoinjector, single accelerator section, and beam diagnostics. Beam quality must be exceedingly high in order to produce narrow-bandwidth gamma-rays, requiring a robust state of the art photoinjector. The photoinjector will be a high gradient (200 MV/m peak surface field on the cathode) standing wave structure, featuring a dual feed racetrack coupler, elliptical irises, and an optimized first cell length. A solid-state Scandinova modulator will power a single SLAC XL4 11.424 GHz 50 MW klystron. RF distribution will allow for full powering of the photoinjector with the balance of the RF powering a single accelerator section so that the electron parameters can be measured. The status of the facility will be presented including commissioning schedule and first experiment plans. Future experimental programs pertinent to Compton scattering R&D, high gradient structure testing, and light source development will be discussed.

MOPC071

Status of High Power Tests of Normal Conducting Short Standing Wave Structures*

coupling, klystron, status, beam-loading

241

V.A. Dolgashev, Z. Li, S.G. Tantawi, A.D. Yeremian
SLAC, Menlo Park, California, USA
Y. Higashi
KEK, Ibaraki, Japan
B. Spataro
INFN/LNF, Frascati (Roma), Italy

Funding: Work Supported by Doe Contract No. DE-AC02-76SF00515
We report results of continuing high power tests of short standing wave structures. These tests are part of an experimental and theoretical study of basic physics of rf breakdown in 11.4 GHz, normal conducting structures. The goal of this study is to determine the accelerating gradient capability of normal conducting rf powered particle accelerators. We have tested structures of different geometries, cell joining techniques, and materials. We found that the breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for cylindrically symmetric structures powered via a TM01 mode launcher. We report test results for structures powered by side-coupled rectangular waveguides. We found that increased rf magnetic field due to the side-coupling increases the breakdown rate as compared to the same accelerating gradient in cylindrically symmetric structures.

MOPC073

A Dual-mode Accelerating Cavity to Test RF Breakdown Dependence on RF Magnetic Fields

cavity, simulation, radio-frequency, vacuum

247

A.D. Yeremian, V.A. Dolgashev, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: * Work Supported by Doe Contract No. DE-AC02-76SF00515
RF Breakdown experiments on short accelerating structures at SLAC have shown that increased rf magnetic fields increase the probability of rf breakdowns. Moreover, the breakdown rate is highly correlated with the peak pulse-heating in soft-copper single-cell standing-wave structures of disk-loaded waveguide type. In these geometries the rf electric and magnetic fields are highly correlated. To separate effects of rf magnetic and electric fields on the rf breakdown rate, we have designed an X-band cavity with a geometry as close to that of a standing-wave accelerator cell as practically possible. This cavity supports two modes: an accelerating TM mode and a TE mode with no-surface-electric field but with a strong magnetic field. The cavity will be constructed and tested at the Accelerator Structure Test Area (ASTA) at SLAC.

MOPC082

Status of the 325 MHz SC CH-Cavity at IAP Frankfurt

cavity, simulation, linac, status

265

M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher
HIM, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: BMBF contract no. 06FY161I
At the Institute for Applied Physics (IAP), University of Frankfurt, a s.c. 325 MHz CH-Cavity is under development for future beam tests at GSI UNILAC, Darmstadt. The cavity with 7 accelerating cells has a geometrical beta of 0.15 corresponding to 11.4 AMeV. The design gradient is 5 MV/m. The geometry of this resonator was optimized with respect to a compact design, low peak fields, surface processing, power coupling and tuning. Furthermore a new tuning system based on bellow tuners inside the resonator will control the frequency during operation. After rf tests in Frankfurt the cavity will be tested with a 10 mA, 11.4 AMeV beam delivered by the GSI UNILAC. In this paper rf simulations, multipacting analysis as well as thermal calculations will be presented.

MOPC092

Effect of Current Densities on Sulfur Generation at Electropolished Niobium Surface

cavity, niobium, cathode, vacuum

292

P.V. Tyagi
Sokendai, Ibaraki, Japan
H. Hayano, S. Kato, M. Nishiwaki, T. Noguchi, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

We conducted a series of electropolishing (EP) experiments in aged EP acid with high (≈50 mA/cm²) and low (≈30 mA/cm²) current densities on Nb surfaces. The experiments were carried out both for laboratory coupons and a real Nb single cell cavity with six witness samples located at three typical positions (equator, iris and beam pipe). All the samples surface were investigated by XPS (x-ray photoelectron spectroscopy), SEM (scanning electron microscope) and EDX (energy dispersive x-ray spectroscopy). The surface analysis showed the EP with a high current density produced a huge amount sulfate particles at Nb surface whereas the EP with a low current density is very helpful to mitigate sulfate at Nb surface in both the experiments.

MOPC093

Novel Field Emission Scanner for Surface Study of Niobium SRF Cavity

cavity, SRF, site, controls

295

S. Kato, M. Nishiwaki, T. Noguchi
KEK, Ibaraki, Japan
V. Chouhan
GUAS, Kanagawa, Japan
P.V. Tyagi
Sokendai, Ibaraki, Japan

It is mandatory to investigate field emission on Nb SRF cavity systematically since strong field emission often limits the cavity performance. The field emission strength and the number of emission sites strongly depend on Nb surface properties which are determined by its surface treatment and handling. Field emission scanner (FES) developed allows us to measure a distribution of the field emitting sites over a sample surface at a given field strength along with its FE-SEM observation and energy dispersive x-ray analysis. FES consists of an anode needle driven by precise 3D stepping motors and an eucentric sample stage. The compact scanner was installed into the space between the object lens and the SEM sample holder. In addition, this system was newly equipped with a sample load-lock system for existing UHV suitcases. Therefore a sample coupon to be observed is hardly exposed to contaminants and dust particles during the transportation. In-situ heating of a sample coupon can be done during an experiment to simulate a baking process of a SRF cavity. This article describes development of the field emission scanner and its preliminary results of the application to niobium samples.

MOPC101

Vertical Test of PEFP Prototype SRF Cavity

cavity, accelerating-gradient, linac, SRF

307

H.S. Kim, Y.-S. Cho, H.-J. Kwon
KAERI, Daejon, Republic of Korea

Funding: This work was supported by Ministry of Education, Science and Technology of the Korean Government.
The PEFP Proton linac is a 100-MeV machine which consists of a proton injector, a 3-MeVRFQ and 100-MeV DTL. For the extension of the machine beyond 100 MeV, SRF technology is under consideration. As a prototyping activity, a superconducting RF cavity with a geometrical beta of 0.42 and a resonant frequency of 700 MHz has been designed, fabricated and tested. The cavity is an elliptical shape with 5 cells stiffened by double-ring structure. A design accelerating gradient is 8.0 MV/m at the operating temperature of 4.2 K and maximum duty factor is 9%. For the vertical test of the cavity, a cryostat with a vacuum jacket and multi-layer insulation was prepared. The RF system for driving the cavity is based on PLL to track the resonant frequency. In case of lack of RF power, a two-way RF power combiner based on splitted coaxial transmission line is considered. The details of the vertical test setup and test results will be presented in this paper.

MOPC112

Fabrication and Testing Status of CEBAF 12 GeV Upgrade Cavities

cavity, cryomodule, HOM, status

337

F. Marhauser, A. Burrill, G.K. Davis, D. Forehand, C. Grenoble, J. Hogan, R.B. Overton, A.V. Reilly, R.A. Rimmer, M. Stirbet
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The 12 GeV upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) is under way. All cavities have been built by industry and are presently undergoing post-processing and final low and high power qualification before cryomodule assembly. The status is reported including fabrication-related experiences, observations and issues throughout production, post-processing and qualification.

MOPC114

Design, Fabrication and Testing of Medium-Beta 650 MHz SRF Cavity Prototypes for Project-X

cavity, SRF, linac, vacuum

343

F. Marhauser, W.A. Clemens, J. Henry, P. Kneisel, R. Martin, R.A. Rimmer, G. Slack, L. Turlington, R.S. Williams
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A new type of superconducting radio frequency (SRF) cavity shape with a shallow equator dome to reduce electron impact energies for suppressing multipacting barriers has been proposed. The shape is in consideration for the first time in the framework of Project-X to design a potential multi-cell cavity candidate for the medium-beta section of the SRF proton CW linac operating at 650 MHz. Rationales covering the design of the multi-cell cavity, the manufacture, post-processing and high power testing of two single-cell prototypes are presented.

MOPC116

Development of Nb and Alternative Material Thin Films Tailored for SRF Applications

SRF, ECR, cavity, ion

349

A-M. Valente-Feliciano, H.L. Phillips, C.E. Reece, J.K. Spradlin, B. Xiao, X. Zhao
JLAB, Newport News, Virginia, USA
H. Baumgart, D. Gu
ODU, Norfolk, Virginia, USA
D. Beringer, R.A. Lukaszew
The College of William and Mary, Williamsburg, USA
K.I. Seo
NSU, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S.DOE Contract No. DE-AC05-06OR23177.
Over the years, Nb/Cu technology, despite its shortcomings due to the commonly used magnetron sputtering, has positioned itself as an alternative route for the future of superconducting structures used in accelerators. Recently, significant progress has been made in the development of energetic vacuum deposition techniques, showing promise for the production of thin films tailored for SRF applications. JLab is pursuing energetic condensation deposition via techniques such as Electron Cyclotron Resonance and High Power Impulse Magnetron Sputtering. As part of this project, the influence of the deposition energy on the material and RF properties of the Nb thin film is investigated with the characterization of their surface, structure, superconducting properties and RF response. It has been shown that the film RRR can be tuned from single digits to values greater than 400. This paper presents results on surface impedance measurements correlated with surface and material characterization for Nb films produced on various substrates, monocrystalline and polycrystalline as well as amorphous. A progress report on work on NbTiN and AlN based multilayer structures will also be presented.

MOPC123

Temperature Dependent Microphonics in the BNL Electron Cooler*

resonance, cavity, linac, cryogenics

370

P. Jain
Stony Brook University, Stony Brook, USA
I. Ben-Zvi, C. Schultheiss
BNL, Upton, Long Island, New York, USA

An R&D Energy Recovery Linac (ERL), to be used in the BNL electron cooler, has been operational in a developmental setting. The ERL requires a cryogenic system to supply cooling to a superconducting RF gun and the 5-cell superconducting RF cavity system that is kept cold at 2K. The 2K superfluid bath is produced by pumping on the bath using a sub-atmospheric warm compression system. During a test run in October 2010, a resonance peak corresponding to a noise of 30 Hz was observed at 1.88K. This noise peak, present at all temperatures below 2K, is assumed to be of mechanical origin from the vibration of the cryopump. Another resonance noise peak of 16 Hz, characteristic of the system, was observed at 1.98K, which shifted towards the 30 Hz peak as the temperature of the cryostat varied from 1.98K to 1.88K. The 16 Hz resonance peak upon hitting the 30 Hz resonance peak, sets a resonance condition, thereby the 30 Hz peak getting amplified by more than five times. In this paper we explore the origin of the temperature dependent 16 Hz resonance peak and give a physical explanation of the resonance.

MOPC134

Multifrequency High Power Microwave Electric-vacuum Devices

klystron, vacuum, acceleration, cavity

391

K.G. Simonov, A.A. Borisov, A.V. Galdetsky, A.N. Korolev, A.V. Mamontov
ISTOK, Moscow Region, Russia
O.A. Morozov
Research and Production Co. "MAGRATEP", Fryazino, Russia

A new approach for the design of the multifrequency high power microwave vacuum devices is proposed. These devices provide simultaneously some output phased signals with operating frequencies ω, 2 ω, , nω while input frequency is ω. For example, it is possible obtain output power at frequencies ω and 2ω by using of double-gap output resonator tuned on two modes – sinphased mode at 2ω and antiphased mode at frequency ω. It is possible obtain power at four frequencies ω, 2ω, 3ω and 6ω by using of the two double-gap output resonators placed one inside the other. It is possible obtain power at multiple frequencies by using of the special coaxial resonator. A microwave vacuum device has been fabricated in which power was extracted at nine multiple frequencies simultaneously. The output signal has form of pulses with ultrashort duration and superhigh repetition frequency equal to the input signal frequency ω. Multifrequency high power microwave vacuum devices can be used for the development of compact accelerators of charged particles.

MOPC138

Practical Test of the Linac4 RF Power System

klystron, linac, cavity, controls

403

N. Schwerg, O. Brunner
CERN, Geneva, Switzerland

Linac4 is a linear accelerator for negative Hydrogen ions which will replace the old Linac2 as injector for the CERN accelerators. Its higher energy of 160 MeV will increase the beam intensity in the downstream machines. The normal-conducting accelerating structures are housed in a 100 m long tunnel which will be connected to the existing chain of accelerators and can be extended into a new injector chain. The high RF power for the Linac4 accelerating structures will be generated by thirteen 1.3 MW klystrons, previously used for the CERN LEP accelerator, and six new klystrons of 2.8 MW all operating at a frequency of 352.2 MHz. The re-use of existing LEP equipment, space limitations in the installation and tight phase and amplitude constraints pose a number of challenges for the integration of the RF power system. The power distribution scheme features a folded magic-tee feeding the power from a 2.8 MW klystron to two LEP circulators. We present first results from the Linac4 test place, validating the approach and the used components as well as reporting on the klystron re-tuning activities.

MOPC144

Autocorrelation Function and Power Spectrum of a Train of Quasiperiodic Sequence of Pulses

FEL, wakefield, free-electron-laser, optics

415

E.M. Laziev, B. Grigoryan, V.M. Tsakanov
CANDLE, Yerevan, Armenia
M. Movsisyan, D.L. Oganesyan
YSU, Yerevan, Armenia

The statistical relationship of the autocorrelation function and spectrum of a train of quasi-periodic sequence of pulses having a time jitter of the repetition rate is obtained. Presented the accordance of autocorrelation function as well as power spectrum of the bounded quasi-periodic sequence of pulses and timing jitter of their repetition rate. The results can be used at the measurements of timing jitter of a train of electron bunches.

MOPC148

Optical Clock Distribution System at the ALICE Energy Recovery Linac

pick-up, laser, FEL, feedback

427

T.T. Ng, S.P. Jamison
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Highly stable clock distribution across future light sources is important for the synchronisation of beam generation, manipulation and diagnostics with photon experiments. Optical fibre technology can be used to combat the stability challenges in distributing clock signals over long distances with coaxial cable. We report here on the status of the optical clock distribution system installed on the ALICE energy recovery linac which uses the propagation of ultra-short optical pulses to carry the clock signal. We also present the characterisation of a beam arrival monitor suitable using <40 pC bunch charges and 7 mW, sub-100 fs distributed clock pulses.

MOPC154

RF Photo Gun Stability Measurement at PITZ

gun, laser, feedback, cavity

442

I.I. Isaev, H.-J. Grabosch, M. Gross, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
M.A. Khojoyan
YerPhI, Yerevan, Armenia
D. Richter
HZB, Berlin, Germany
A. Shapovalov
NRNU MEPHI, Moscow, Russia
I.H. Templin, I. Will
MBI, Berlin, Germany

The stability of the RF phase in the RF photo injector gun is one of the most important factors for the successful operation of linac based free-electron lasers. Instabilities in the RF launch phase can significantly reduce the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. The phase stability of the RF field is measured using the phase scan technique. Measurements were performed for different operating conditions at the Photo Injector Test facility at DESY, location Zeuthen (PITZ). Obtained stability measurement results will be presented and discussed.

MOPO037

Concept of Femtosecond Timing and Synchronization Scheme at ELBE

laser, controls, status, pick-up

565

M. Kuntzsch, A. Büchner, M. Gensch, A. Jochmann, T. Kirschke, U. Lehnert, F. Röser
HZDR, Dresden, Germany
M.K. Bock, M. Bousonville, M. Felber, T. Lamb, H. Schlarb, S. Schulz
DESY, Hamburg, Germany

The Radiation Source ELBE at Helmholtz-Zentrum Dresden-Rossendorf is undergoing an extension to offer capacity for various applications. The extension includes the setup of a THz-beamline with a dedicated laboratory and a beamline for electron-beam - high-power laser interaction. The current synchronization scheme offers stability on the picoseconds level. For pump-probe experiments using optical lasers, the desired synchronization between the pump and the probe pulse should be on the femtosecond scale. In the future there will be an optical synchronization system with a pulsed fiber laser as an optical reference. The laser pulses will be distributed over stabilized fiber links to the remote stations. It is planned to install EOM-based beam arrival time monitors (BAMs) in order to monitor the bunch jitter and to establish a beam-based feedback to reduce the jitter. Besides that, the timing system has to be revised to generate triggers for experiments with low repetition rate, two electron guns (thermionic DC, superconducting RF) and several lasers. The Poster will show the possible layout of the future Timing and Synchronization System at ELBE.

MOPO042

Photonic Crystal Fibre Laser for Electron Beam Emittance Measurement*

laser, emittance, diagnostics, extraction

577

L. Corner, L.J. Nevay, R. Walczak
Oxford University, Physics Department, Oxford, Oxon, United Kingdom

We discuss the recent progress in the development of a high repetition rate, high energy fibre laser for intratrain laser-wire scans of transverse electron beam sizes. A commercial fibre laser (1uJ, 6.49MHz) is amplified in rod type photonic crystal fibre using a burst mode format, which has the advantage of allowing us to exploit very high transient gain while reducing the heat load deposited in the amplifier. The amplified pulses are over 180uJ spaced at 154ns, suitable for intratrain scanning at the ATF2. The spatial beam quality is excellent (M2 = 1.07), indicating that it will be possible to focus the laser to a spot size of ~ λ, enabling us to reach high intensities. The amplified pulse duration is 200ps, which can be compressed to less than the electron bunch length to increase the laser-wire signal to noise ratio. The performance of the laser system is analysed with respect to the demands of the laser-wire experiment.

MOPO043

Applications of Lasers to Accelerator Physics at SSRL

laser, gun, cathode, photon

580

D.L. Robinson
Cal Poly, San Luis Obispo, California, USA
W.J. Corbett
SLAC, Menlo Park, California, USA

Recent advances in accelerator physics and SR research have generated the need for high-power lasers in the SPEAR3 accelerator complex. On the injector side, two lasers are being used to test different photocathode materials and to provide photo-assisted emission from the standard dispenser cathode RF gun. For the storage ring, both a TiSa oscillator and a fiber laser locked to the RF master oscillator have been used to characterize short-pulse electron bunches in cross-correlation experiments. These lasers are also used in SR experiments for pump-probe characterization of materials. In this paper we review the laser-based systems, preliminary results and outlook for the future.

MOPS001

Electron-cloud Pinch Dynamics in Presence of Lattice Magnet Fields

proton, cyclotron, quadrupole, simulation

586

G. Franchetti
GSI, Darmstadt, Germany
F. Zimmermann
CERN, Geneva, Switzerland

The pinch of the electron cloud due to a passing proton bunch was extensively studied in a field free region and in a dipolar magnetic field. For the latter study, a strong field approximation helped to formulate the equations of motion and to understand the complex electron pinch dynamics, which exhibited some similarities with the field-free situation. Here we extend the analysis to the case of electron pinch in quadrupoles and in sextupoles. We discuss the limits of validity for the strong field approximation and we evaluate the relative magnitude of the peak tune shift along the bunch expected for the different fields.

MOPS011

Impact of Low Transition Energy Optics to the Electron Cloud Instability of LHC Beams in the SPS

optics, simulation, synchrotron, emittance

616

H. Bartosik, E. Benedetto, K.S.B. Li, Y. Papaphilippou, G. Rumolo
CERN, Geneva, Switzerland

One of the main limitations for high intensity multi-bunch LHC proton beams in the SPS is imposed by electron cloud instabilities. A new optics of the SPS with lower transition energy was implemented and successfully tested in machine studies. The significant increase of the slippage factor that it provides at injection energy results in the expected increase of the single bunch instability thresholds. In this paper, the impact of this new optics on the electron cloud instability threshold is estimated by using numerical simulations, taking into account the change of the optics functions and the faster synchrotron motion due to the reduced transition energy.

MOPS024

Bunch Dynamics through Accelerator Column

space-charge, TRIUMF, gun, cathode

649

R.A. Baartman
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

Funding: TRIUMF research is supported by the National Research Council of Canada.
The differential equations for the bunched beam envelope through an axially symmetric DC accelerator are derived. In the case of no space charge, a particle's total energy is conserved, so the longitudinal evolution is simple: particles of same energy are a fixed time increment apart and this implies in first order that their separation is proportional to their speed. However, with space charge, the longitudinal force depends upon the bunch length, so we need equations that track this parameter. The full 6-dimensional and relativistically correct envelope equations are derived.

MOPS029

Experiments with a Fast Chopper System for Intense Ion Beams

ion, space-charge, simulation, high-voltage

664

H. Dinter, M. Droba, M. Lotz, O. Meusel, I. Müller, D. Noll, U. Ratzinger, K. Schulte, C. Wagner, C. Wiesner
IAP, Frankfurt am Main, Germany

Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ, an E×B chopper system is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50 ns at a repetition rate of 250 kHz for 120 keV, 200 mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6 kV and the resulting response was measured using a beam current transformer. A comparison between experiments and theoretical calculations as well as numerical simulations are presented.

MOPS033

Beam Dynamics Studies on the 100 MeV/100 kW Electron Linear Accelerator for NSC KIPT Neutron Source

linac, dipole, gun, simulation

673

S. Pei, Y.L. Chi, M. Hou, W.B. Liu, G. Pei, S.H. Wang, Z.S. Zhou
IHEP Beijing, Beijing, People's Republic of China
N. Aizatsky, I.M. Karnaukhov, V.A. Kushnir, V. Mitrochenco, A.Y. Zelinsky
NSC/KIPT, Kharkov, Ukraine

We designed one 100MeV/100kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the base of subcritical assembly. Beam dynamics studies has been conducted to reach the design requirement (E=100MeV, P=100kW, dE/E<1% for 99% particles). In this paper, we will present the progress of the design and dynamics simulation results. For high intensity and long beam pulse linear accelerators, BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced at the downstream of the 1st accelerating section; the unwanted particles will be collimated there.

MOPS034

Progress on Space Charge Compensation Study in Low Energy High Intense H⁺ Beam*

emittance, injection, ion, space-charge

676

P.N. Lu, Z.Y. Guo, S.X. Peng, Z.X. Yuan, J. Zhao
PKU/IHIP, Beijing, People's Republic of China
H.T. Ren
Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China

This article lays emphasis on the relationship between the Space Charge Compensation (SCC) and the beam quality in different conditions. Ar and Kr are used to compensate a 35keV/90mA H⁺ beam with the gas pressure from 3.7×10^-4 Pa to 6×10^-3 Pa. Experiments are conducted in different compensation states with three approaches. With an energy spectrometer, we have got the energy spectra of Extra Compensation Gas Ions (ECGI). By a beam profile meter, the beam profiles are obtained when the injection of compensation gas is gradually rising. In the meantime, the beam emittance is measured under different compensation conditions. After measurements of the above data, the potential and the rest charge distributions in the beam are calculated by analyzing the ECGI energy spectra and beam profiles. All experiments performed aimed to seek out the best circumstance for SCC dominated low energy high intensity ion beams.together to calculate the potential distribution are calculated by analyzing the energy spectra and beam profiles. All experiments performed aimed to seeking for the best circumstances in SCC dominated low energy high intensity ion beams.

MOPS035

Energy Spreads by Transient Beam Loading Effect in Pulsed RF Linac

gun, linac, bunching, beam-loading

679

S.H. Kim, M.-H. Cho, G. Ha, H.R. Yang
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Namkung, S.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
J.-S. Oh
NFRI, Daejon, Republic of Korea

Funding: Work partly supported by KAPRA and POSTECH Physics BK21 Program
RF linacs for high power beams are operated in the fully beam-loaded condition for the power efficiency. In this condition, temporal energy spreads are induced by the transient beam loading effect. Irradiation sources require the beam energy of less than 10 MeV to prevent undesirable neutron production. In order to maximize the beam power and maintain the beam energy in a safe value, we need to suppress the temporal energy spreads. In an L-band traveling-wave linac for irradiation sources, the high energy electrons are suppressed by the beam current modulation with the RF power modulation. As a result, the average beam energy and the corresponding beam power are improved by nearly 60% compared to the case without any modulations.

MOPS037

High Intensity Transient Beam Dynamic Study in Travelling Wave Electron Accelerators with Accounting of Beam Loading Effect

simulation, beam-loading, linac, space-charge

682

S.M. Polozov, T.V. Bondarenko, E.S. Masunov, V.I. Rashchikov, A.V. Voronkov
MEPhI, Moscow, Russia

The beam loading effect is one of main problems limiting the beam current. The methods of beam dynamic simulation taking into account the beam loading effect were discussed previously. Simulation methods and the especial code version BEAMDULAD-BL was described in the paper*. The beam loading effect was considered only for traveling wave linacs and for stationary beam only. Now it is important to study the beam dynamics of short current pulses, i.e. for transient process. We can consider only one beam bunch (or a packet of bunches) in a long external RF field pulse in stationary case. The beam radiation and wave fields can be calculated in the quasi-statically approximation. This approximation can not be used for transient mode. The methods of beam dynamics simulation will be discussed in this paper for transient mode. New code version BEAMDULAC-BLNS will be described. The simple test simulations will be carried out.
* A.V. Voronkov et al., "Beam Loading Effect of High Current Trawling Wave Accelerator Dynamic Study", Proc. of IPAC’10, Kyoto, Japan, TUPEA012, p. 1348 (2010).

MOPS040

Intra-Bunch Energy Spread of Electrons in Powerful RF Linacs for Nuclear Physics Research*

linac, target, HOM, simulation

691

V.V. Mytrochenko, M.I. Ayzatskiy, V.A. Kushnir, A. Opanasenko, S.A. Perezhogin, V.L. Uvarov
NSC/KIPT, Kharkov, Ukraine

Funding: Ukrainian State program of fundamental and applied studies on the use of nuclear materials, nuclear and radiation technologies in the fields of economics (YaMRT project No. 826/35)
There are some particles in RF electron linacs with energy that may be significantly different from that of particles within a core of the bunch. Loss of these particles at average beam power of tens of kilowatts can cause radiation and thermal problems. Filtration of such particles during the initial stage of acceleration, at energies below the threshold of photonuclear reactions, is important. The paper analyzes several ways to perform such type of filtration in the injector part of a powerful electron linac using a RF chopper or magnetic systems.

MOPS042

One-Dimensional Adiabatic Child-Langmuir Flow

simulation, emittance, gun, plasma

694

C. Chen
MIT, Cambridge, Massachusetts, USA
R. Pakter, F.B. Rizzato
IF-UFRGS, Porto Alegre, Brazil

Funding: Research supported in part by US Department of Energy, Grant No. DE-FG02-95ER40919, CNPq, FAPERGS, INCTFCx of Brazil, and US Air Force Office of Scientific Research, Grant No. FA9550-09-1-0283.
A theory is presented that describes steady-state one-dimensional Child-Langmuir flow at a self-consistent finite temperature distribution. In particular, warm-fluid equations and adiabatic equation of state are used to derive the self-consistent Poisson equation. The profiles of the charged-particle density, the velocity, the electrostatic potential, the pressure and the temperature are computed. Results are compared with self-consistent simulations.

MOPS048

Microbunching Instability Studies at SOLEIL

radiation, storage-ring, synchrotron, synchrotron-radiation

709

C. Evain, J. Barros, J.B. Brubach, L. Cassinari, M.-E. Couprie, G. Creff, M. Labat, A. Loulergue, L. Manceron, R. Nagaoka, P. Roy, M.-A. Tordeux
SOLEIL, Gif-sur-Yvette, France

Microbunching instability arises in storage rings when the number of electrons in a bunch exceeds a threshold value. Its signature, i.e. a strong and irregular emission of Coherent Synchrotron Radiation (CSR) in the Terahertz (THz) domain, is studied at SOLEIL on the AILES infrared beamline, with the storage ring tuned in a low-alpha configuration (used to get shorter electron bunch). The comparison of this observed THz CSR with numerical simulations of the longitudinal electron bunch dynamics, permits to put in evidence that during the instability a modulation appears and drifts in the longitudinal profile of the electron bunch. The understanding of this instability is important as it limits some operation of the storage rings. Indeed the induced fluctuations prevent the use of THz on the far IR beamline at high current per bunch. And in normal alpha operation this instability may spoil the electron/laser interaction effects used to get femtosecond and/or coherent pulse in storage rings (with slicing, Coherent Harmonic Generation or EEHG schemes on storage ring).

MOPS049

Study of Ion-induced Instabilities and Transverse Feedback Performance at SOLEIL

ion, feedback, vacuum, simulation

712

R. Nagaoka, L. Cassinari, M.D. Diop, J.-M. Filhol, M.-P. Level, A. Loulergue, P. Marchand, R. Sreedharan
SOLEIL, Gif-sur-Yvette, France

Experimental studies indicate that the SOLEIL storage ring at its maximum designed current of 500 mA is under a large influence of ions, potentially capable of inducing the so called fast beam-ion instability. To avoid it, the following three conditions have been empirically found effective: A reduced RF voltage, uniform filling and a large vertical chromaticity. While the choice of uniform filling appears contradictory to raising the ion instability threshold, it goes well with lowering of the RF voltage if outgassing due to beam-induced heating of the vacuum components is the primary source of ions. Additional difficulties associated are frequent occurrence of sudden beam blowups despite the presence of transverse feedback, which are large enough to trigger machine interlocks leading to complete beam losses. These blow ups may even take place horizontally inside in-vacuum insertion devices. The present paper reports on the results and findings obtained through experimental and simulation studies carried out on the collective beam dynamics and the transverse feedback performance, which are deeply interlinked, in order to clarify the mechanism of the encountered phenomena.

MOPS050

Electron Beam Dynamics in the 50 MeV ThomX Compact Storage Ring

emittance, scattering, photon, collective-effects

715

C. Bruni, J. Haissinski
LAL, Orsay, France
A. Loulergue, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France

ThomX is a high flux compact X-ray source based on Compton back scattering between a relativistic electron beam and an intense laser pulse. To increase the repetition rate, the electron beam is stored in a ring. The main drawback of such a scheme is the low energy of the electrons regarding collective effects and intrabeam scattering. These effects tend to enlarge or even disrupt the stored bunch and they limit its charge, especially in a system where damping plays a negligible role. Thus such collective effects reduce the maximum X-ray flux and it is important to investigate them to predict the performance of this type of X-ray source. In addition, the Compton back scattering acts on the electron beam by increasing its energy spread. This presentation will show firstly the impact of collective effects on the electron beam, essentially during the first turns when they are the most harmful. Then, the reduction of the X-ray flux due to Compton back scattering and intrabeam scattering will be investigated on a longer time scale.

MOPS053

Electron Cloud Effects in Coasting Heavy-ion Beams*

simulation, ion, accumulation, dipole

724

F.B. Petrov, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim
GSI, Darmstadt, Germany

Funding: Work supported by BMBF under contract 06DA9022I.
During slow extraction of intense ion beams electron clouds (EC) can accumulate in the circulating coasting beam and reduce the extraction efficiency. This is a concern for the existing SIS-18 heavy ion synchrotron at GSI and for the projected SIS-100 as part of the FAIR project. For medium energy heavy-ion beams the production of electrons from residual gas ionization is very effective. The electron density is limited due to Coulomb scattering by the beam ions. Above a threshold beam intensity the two-stream instability and the resulting coherent beam oscillations limit the electron density. Below this threshold the electron cloud can lead to observable deformations of the Schottky side-bands. To avoid EC build-up one can introduce a gap in the beam using barrier rf bucket. The reduction of the build-up efficiency caused by the gap is studied in details based on the solution of the Hill's equation for electrons. Finally we estimate the saturation level for the electron cloud density.

MOPS055

Observation of Intensity Dependent Single Bunch Effects at the Synchrotron Light Source PETRA III

impedance, emittance, synchrotron, single-bunch

730

R. Wanzenberg, K. Balewski
DESY, Hamburg, Germany

At DESY the PETRA ring is operated as a synchrotron radiation facility with a very low emittance of 1 nm. Regular user operation has started in summer 2010. A summary of observations and measurements of intensity dependent single bunch effects is presented in this report. The longitudinal impedance of the ring is estimated from the measured bunch length versus beam intensity. The results are compared with predictions from the impedance model. Furthermore measurements of the single bunch intensity limit due to the transverse mode coupling instability (TMCI) are reported. The tune and phase shift around the ring has been measured as a function of the beam intensity. At PETRA III tune spectra have been observed with some characteristics which have been observed at other storage rings in connection with electron cloud effects. The present status of the observations of potential electron cloud effects is also discussed.

MOPS056

An Analytical Formula of the Electron Cloud Linear Map Coefficient in a Strong Dipole

dipole, vacuum, simulation, storage-ring

733

T. Demma
INFN/LNF, Frascati (Roma), Italy
S. Petracca, A. Stabile
U. Sannio, Benevento, Italy
G. Rumolo
CERN, Geneva, Switzerland

Electron cloud effects have been indentified as one of the most serious bottleneck for reaching design performances in presently running and proposed future storage rings. The analysis of these effects is usually performed with very time consuming simulation codes. An alternative analytic approach, based on a cubic map model for the bunch-to-bunch evolution of the electron cloud density, could be useful to determine regions in parameters space compatible with safe machine operations. In this communication we derive a simple approximate formula relating the quadratic coefficient in the electron cloud density map to the parameters relevant for the electron cloud evolution in a strong vertical magnetic field. Results are compared with simulations with particular reference to the LHC dipoles.

MOPS057

Beam-beam Interaction under External Force Oscillation

luminosity, positron, simulation, kicker

736

K. Ohmi
KEK, Ibaraki, Japan

Beam-ion interaction is strongly nonlinear. Response for external oscillation applied to beam shows characteristic feature. Simulations for external frequency scan becomes feasible for the recent computer power. We show the frequency response for beam-ion system in KEK-PF and recent low emittance rings.

MOPS069

Review of Beam Instabilities in the Presence of Electron Clouds in the LHC

emittance, injection, simulation, luminosity

760

K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland

Recent observations at the LHC indicate the build-up of electron clouds when 50 ns spaced beams are injected into the machine at nominal intensity. These electron clouds are a source of coherent beam instabilities and incoherent emittance growth and limit the achievable luminosity. To better understand the influence of electron clouds on the beam dynamics, simulations have been carried out to study both the coherent and the incoherent effects on the beam. The simulations are performed with the HeadTail tracking code; the usage of new post-processing software allows determining not only the beam intensity thresholds in terms of the central electron cloud density but also the footprint of the beam in tune space. In this paper we review instability thresholds and tune footprints for beams with different emittances and interacting with an electron cloud in field-free or dipole regions.

MOPS083

Update on Electron Cloud Mitigation Studies at Cesr-TA*

wiggler, positron, resonance, photon

796

J.R. Calvey, M.G. Billing, J.V. Conway, G. Dugan, S. Greenwald, Y. Li, X. Liu, J.A. Livezey, J. Makita, R.E. Meller, M.A. Palmer, S. Santos, R.M. Schwartz, J.P. Sikora, C.R. Strohman
CLASSE, Ithaca, New York, USA
S. Calatroni, G. Rumolo
CERN, Geneva, Switzerland
K. Kanazawa, Y. Suetsugu
KEK, Ibaraki, Japan
M.T.F. Pivi, L. Wang
SLAC, Menlo Park, California, USA

Funding: Work supported by the US National Science Foundation (PHY-0734867) and Department of Energy (DE-FC02-08ER41538)
Over the course of the past three years, the Cornell Electron Storage Ring (CESR) has been reconfigured to serve as a test facility for next generation particle accelerators. A significant part of this program has been the installation of several diagnostic devices to measure and quantify the electron cloud effect, a potential limiting factor in these machines. In particular, more than 30 Retarding Field Analyzers (RFAs) have been installed in CESR. These devices measure the local electron cloud density and energy distribution, and can be used to evaluate the efficacy of different cloud mitigation techniques. This paper will provide an overview of RFA results obtained at CesrTA over the past year, including measurements taken as function of bunch spacing and wiggler magnetic field. Understanding these results provides a great deal of insight into the behavior of the electron cloud.

MOPS084

Status of Electron Cloud Dynamics Measurements at CESRTA*

dipole, betatron, damping, feedback

799

M.G. Billing, G. Dugan, M.J. Forster, D.L. Kreinick, R.E. Meller, M.A. Palmer, G. Ramirez, M.C. Rendina, N.T. Rider, J.P. Sikora, K.G. Sonnad, H.A. Williams
CLASSE, Ithaca, New York, USA
J.Y. Chu
CMU, Pittsburgh, Pennsylvania, USA
J.W. Flanagan
KEK, Ibaraki, Japan
R. Holtzapple, M. Randazzo
CalPoly, San Luis Obispo, California, USA

Funding: Supported by US National Science Foundation (PHY-0734867) & Dept. of Energy (DE-FC02-08ER41538)
The study of electron cloud-related instabilities for the CESR-TA project permits the observation of the interaction of the electron cloud with the stored beam under a variety of accelerator conditions. These measurements are undertaken utilizing automatic and semi-automatic techniques for three basic observations: the measurement of tune shifts of individual bunches along a train, the detection of the coherent self-excited spectrum for each bunch within a train and the pulsed excitation of either the betatron dipole or head-tail mode for each individual bunch within the train, followed by the observation of the damping of its coherent motion. These techniques are employed to study the electron cloud-related interactions in a number of conditions, such as trains of bunches with low emittance and spaced by as little as 4 nsec between bunches. We report on the most recent observations and results.

MOPS088

Simulation of Electron Cloud Beam Dynamics for CesrTA

emittance, simulation, betatron, positron

808

K.G. Sonnad, G. Dugan, M.A. Palmer, G. Ramirez, H.A. Williams
CLASSE, Ithaca, New York, USA
K.R. Butler
Cornell University, Ithaca, New York, USA
M.T.F. Pivi
SLAC, Menlo Park, California, USA

This presentation provides a comprehensive set of results obtained using the simulation program CMAD. CMAD is being used for studying electron cloud induced beam dynamics issues for CesrTA, which is a test facility for studying physics associated with electron and positron damping rings. In particular, we take a closer look at electron cloud induced effects on positron beams, including head-tail motion, emittance growth and incoherent tune shifts for parameters specific to ongoing experimental studies at CesrTA. The correspondence between simulation and experimental results will also be discussed.
Work supported by US Department of Energy grant number DE-FC02-08ER41538
and the National Science Foundation grant number PHY-0734867

MOPS091

Study of Electron Cloud for MEIC

simulation, emittance, luminosity, dipole

817

S. Ahmed, J.D. Dolph, G.A. Krafft, T. Satogata, B.C. Yunn
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Medium Energy Electron Ion Collider (MEIC) at Jefferson Lab has been envisioned as a future high energy particle accelerator beyond the 12 GeV upgrade of the existing Continuous Electron Beam Accelerator Facility (CEBAF). Synchrotron radiation from the closely spaced proton bunches in MEIC can generate photoelectrons inside the vacuum chamber and cause secondary emission due to multipacting in the presence of beam's electric field. This phenomenon can lead to fast build up of electron density, known as electron cloud effect – resulting into beam instability coupled to multi-bunches in addition to a single bunch. For MEIC, the estimated threshold value of the electron-cloud density is approximately 5 x 10¹² m-3. In this paper, we would like to report the self-consistent simulation studies of electron cloud formation for MEIC. The code has been benchmarked against the published data of electron cloud effects observed in LHC. Our first simulations predict increase of electron clouds with the increase of repetition rate. The detailed simulations are under progress and will be reported.

MOPZ004

Studies for the PRISM FFAG Ring for the Next Generation Muon to Electron Conversion Experiment

injection, kicker, extraction, septum

826

J. Pasternak
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
M. Aslaninejad, L.J. Jenner, A. Kurup, J. Pasternak, Y. Shi, Y. Uchida
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
R.J. Barlow
UMAN, Manchester, United Kingdom
K.M. Hock, B.D. Muratori
Cockcroft Institute, Warrington, Cheshire, United Kingdom
D.J. Kelliher, S. Machida, C.R. Prior
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
Y. Kuno, A. Sato
Osaka University, Osaka, Japan
J.-B. Lagrange, Y. Mori
KURRI, Osaka, Japan
M. Lancaster
UCL, London, United Kingdom
C. Ohmori
KEK, Tokai, Ibaraki, Japan
T. Planche
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
S.L. Smith
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
H. Witte, T. Yokoi
JAI, Oxford, United Kingdom

High intensity and high quality muon beams are needed for the next generation lepton flavour violation experiments. Such beams can be produced by sending a short proton pulse to a pion production target, capturing the pions and performing RF phase rotation on the resulting muon beam in an FFAG ring. Such a solution was proposed for the PRISM project and this paper summarizes its current status. In particular the PRISM task force was created to address the accelerator and detector issues that need to be solved in order to realise the PRISM experiment. Alternative designs for the PRISM FFAG ring are discussed and their performance compared. The injection/extraction systems and matching to the solenoid channels upstream and downstream of the FFAG ring are presented. The future direction for the study will be outlined.

MOPZ037

Extension of the 3-spectrometer Beam Transport Line for the KAOS Spectrometer at MAMI and Recent Status of MAMI

target, dipole, beam-transport, status

880

R.G. Heine, M. Dehn, K.-H. Kaiser, H.-J. Kreidel, U.L. Ludwig-Mertin
IKP, Mainz, Germany

Funding: Work supported by DFG (CRC443) and the German Federal State of Rhineland-Palatinate
The institute for nuclear physics (KPH) at Mainz University is operating a 1.6 GeV c.w. microtron cascade (MAMI) for nuclear physics research. One of the vast experimental activities is electron scattering. A 3-spectrometer setup is used for cross-section measurements of hadron knock-out and meson production. The KAOS spectrometer magnet of GSI is installed there in parallel to detect particles from (e,e'K)reactions under small forward angles. So the primary electron beam has to transit the spectrometer and after this it has to hit the existing beam dump. Because of the existing experimental setup, this must be realised by deflecting the beam before the target that is rotated to be in line with the KAOS spectrometer's inlet. This paper will deal with the basic concept of a flexible beam transport line (BTL) magnet chicane for different KAOS forward angles, while keeping the forward beam direction for the 3-spectrometer setup untouched. A survey concept for assembly and adjustment of the BTL will be introduced, that is also useful for future adjustments of the target mount after target change. Results of the BTL commissioning and a general MAMI status will be presented as well.

TUYA01

Achievements and Lessons from the Tevatron

antiproton, collider, luminosity, proton

903

V.D. Shiltsev
Fermilab, Batavia, USA

The Tevatron Run-2 will come to an end at the time of IPAC'11. This talk will concentrate on exploration of the accelerator physics issues that were dealt with in achieving the current (very high) level of performance in the Tevatron and will review achievements, challenges and lessons learned on the way.

Slides TUYA01 [5.881 MB]

TUZA01

Commissioning and Initial Operation of FERMI@Elettra

FEL, laser, photon, undulator

918

S. Di Mitri, E. Allaria, R. Appio, L. Badano, S. Bassanese, F. Bencivenga, A.O. Borga, M. Bossi, E. Busetto, C. Callegari, F. Capotondi, K. Casarin, D. Castronovo, P. Cinquegrana, D. Cocco, M. Cornacchia, P. Craievich, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, P. Delgiusto, A.A. Demidovich, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, S. Ferry, V. Feyer, L. Fröhlich, P. Furlan Radivo, G. Gaio, F. Gelmetti, L. Giannessi, R. Gobessi, R. Ivanov, E. Karantzoulis, M. Kiskinova, M. Lonza, A.A. Lutman, C. Masciovecchio, R.H. Menk, M.M. Milloch, M.M. Musardo, I. Nikolov, S. Noe, F. Parmigiani, L. Pavlovič, E. Pedersoli, G. Penco, M. Petronio, M. Predonzani, E. Principi, E. Quai, G. Quondam, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Spezzani, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Wang, M. Zaccaria, D. Zangrando
ELETTRA, Basovizza, Italy
M. Alagia, A. Kivimaki, M. Zangrando, M. de Simone
IOM-CNR, Trieste, Italy
L. Avaldi, P. Bolognesi, M. Coreno, P. O’Keeffe
CNR - IMIP, Trieste, Italy
M. Dal Forno
DIEIT, Trieste, Italy
G. De Ninno, S. Spampinati
University of Nova Gorica, Nova Gorica, Slovenia
M. Devetta, T. Mazza, P. Piseri
Università degli Studi di Milano, Milano, Italy
E. Ferrari
Università degli Studi di Trieste, Trieste, Italy
S. Stranges
Università di Roma "La Sapienza", Roma, Italy

Funding: Work was supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3.
This article describes the design goals of FERMI@Elettra, reports on the goals achieved so far and shows how the facility development has been driven by the new research frontier of ultra-fast, extreme ultra-violet and soft X-ray science. The commissioning phases and first experience with user pilot experiments are presented and discussed.

Slides TUZA01 [13.401 MB]

TUZA02

sFLASH - Present Status and Commissioning Results

undulator, laser, FEL, radiation

923

V. Miltchev, S. Ackermann, A. Azima, J. Bödewadt, F. Curbis, M. Drescher, E. Hass, Th. Maltezopoulos, M. Mittenzwey, J. Rönsch-Schulenburg, J. Roßbach, R. Tarkeshian
Uni HH, Hamburg, Germany
H. Delsim-Hashemi, K. Honkavaara, T. Laarmann, H. Schlarb, S. Schreiber, M. Tischer
DESY, Hamburg, Germany
R. Ischebeck
PSI, Villigen, Switzerland
S. Khan
DELTA, Dortmund, Germany

The free-electron laser in Hamburg (FLASH) was previously being operated in the self-amplified spontaneous emission (SASE) mode, producing photons in the XUV wavelength range. Due to the start-up from noise the SASE-radiation consists of a number of uncorrelated modes, which results in a reduced coherence. One option to simultaneously improve both the coherence and the synchronisation between the FEL-pulse and an external laser is to operate FLASH as an amplifier of a seed produced using high harmonics generation (HHG). An experimental set-up - sFLASH, has been installed to test this concept for the wavelengths below 40 nm. The sFLASH installation took place during the planed FLASH shutdown in the winter of 2009/2010. The technical commissioning, which began in the spring of 2010, has been followed by seeded-FEL commissioning, FEL-characterisation and pilot experiments. In this contribution the present status and the sFLASH commissioning results will be discussed.

Slides TUZA02 [4.125 MB]

TUODA03

The Status of the ALICE Accelerator R&D Facility at STFC Daresbury Laboratory

FEL, radiation, cavity, diagnostics

934

F. Jackson, D. Angal-Kalinin, R. Bate, R.K. Buckley, S.R. Buckley, J.A. Clarke, P.A. Corlett, D.J. Dunning, J.-L. Fernández-Hernando, A.R. Goulden, S.F. Hill, D.J. Holder, S.P. Jamison, J.K. Jones, L.B. Jones, A. Kalinin, S. Leonard, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, A.J. Moss, B.D. Muratori, T.T. Ng, J.F. Orrett, S.M. Pattalwar, Y.M. Saveliev, D.J. Scott, B.J.A. Shepherd, A.D. Smith, R.J. Smith, S.L. Smith, N. Thompson, A.E. Wheelhouse, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
P. Harrison, G.M. Holder, A.L. Schofield, P. Weightman, R.L. Williams, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
M. Surman
STFC/DL/SRD, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Science and Technology Facilities Council
The ALICE accelerator, the first energy recovery machine in Europe, has recently demonstrated lasing of an infra-red free electron laser (IR-FEL). The current status of the machine and recent developments are described. These include: lasing of the IR-FEL, a programme of powerful coherent terahertz radiation research, electro-optic diagnostic techniques, development of high precision timing and distribution system, implementation of digital low level RF control. ALICE also serves as an injector for the EMMA non-scaling FFAG machine.

Slides TUODA03 [1.648 MB]

TUOAB02

Simultaneous Long and Short Bunch Operation in an Electron Storage Ring - a Hybrid Mode based on Nonlinear Momentum Compaction

storage-ring, synchrotron, octupole, photon

945

M. Ries, J. Feikes, A. Jankowiak, P.O. Schmid, G. Wüstefeld
HZB, Berlin, Germany

The generation of short pulses in electron storage rings is driven by different user groups like time resolved x-ray spectroscopy users or users of coherent synchrotron radiation. The required optics and operation conditions to generate this short bunches are worsening the experimental conditions, e.g. strongly reducing the average photon flux, for the regular user. Therefore short bunch operation is usually limited to dedicated user shifts. By controlling higher orders of the momentum compaction factor by higher multipoles it is possible to introduce a hybrid mode and simultaneously supplying long and short bunches*. The Metrology Light Source (MLS) has the means to control these higher orders**, therefore it is an ideal machine to investiate the feasibility of such a hybrid mode. Tracking results and first measurements will be shown.
* D. Robin et al., Proc. of EPAC08, p. 2100-2102, Genoa, Italy (2008).
** J. Feikes et al., Phys. Rev. ST Accel. Beams 14, 030705 (2011).

Slides TUOAB02 [7.817 MB]

TUYB01

First Results from the EMMA Experiment

acceleration, cavity, injection, septum

951

S. Machida
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

Report on first commissioning results and operational experience with EMMA, the world's first nonscaling FFAG. In particular review the effect of resonance crossing, and the efficiency of serpentine acceleration.

Slides TUYB01 [9.201 MB]

TUYB02

The Challenges of Ultra-low Emittance Damping Rings

emittance, damping, quadrupole, coupling

956

D. L. Rubin
CLASSE, Ithaca, New York, USA

Funding: Work supported by the National Science Foundation and by the US Department of Energy under contract numbers PHY-0734867 and DE-FC02-08ER41538.
In this paper we review the state of the art of the design of damping rings for linear colliders, as supported by the experimental data from ATF and CESR test damping rings. We consider implications of measurements of electron cloud dynamics and mitigation in a radiation dominated ring. The techniques developed for tuning for ultra-low emittance in these rings are summarized. Other dynamics manifested in the ultra-low emittance regime where collective effects are important are discussed.

Slides TUYB02 [7.198 MB]

TUODB02

Extreme High Vacuum System of High Brightness Electron Source for ERL

gun, vacuum, ion, cathode

979

M. Yamamoto, T. Honda, Y. Honda, T. Miyajima, Y. Saito, Y. Tanimoto, T. Uchiyama
KEK, Ibaraki, Japan
H. Akimichi, H. Yoshida
AIST, Tsukuba, Japan
H. Kurisu
Yamaguchi University, Ube-Shi, Japan

A compact test accelerator for Japan’s future light source based on energy recovery linac (ERL) is under construction in KEK, aiming to demonstrate key technologies such as a high-brightness photocathode DC-gun and superconducting RF cavities. A DC-gun using GaAs-type photocathode which has a negative electron affinity (NEA) surface is employed. The NEA surface plays an indispensable role to extract electrons from conduction band minimum into vacuum. It assures high quantum efficiency of the photocathode and very low intrinsic emittance of the extracted beam. However, the NEA surface is extremely delicate against residual gas in vacuum. In order to extract mA-level beam currents continuously for more than several tens of hours, the pressure should be lower than the order of ·10^-10 Pa to avid the backbombardment of positive ions produced by the collision of accelerated electrons with residual gas molecules in the beam path. Recent achievements in the development of a 500-kV photocathode DC-gun and in the fundamental studies of its extreme high vacuum system will be presented.

Slides TUODB02 [1.606 MB]

TUPC001

Simulations of the Interaction Point for TeV-scale e⁺ e− Colliders

photon, simulation, collider, radiation

985

J. Esberg
Aarhus University, Aarhus, Denmark

The design of a detector and post collisional line of a future linear collider calls for detailed knowledge of the beam-beam dynamics at the interaction point. We here describe the implementation and results of new simulation tools in the program GUINEA-PIG. The subjects are direct trident production relevant in the deep quantum-regime, incoherent muon generation, synchrotron radiation from secondary particles and depolarization effects. We choose beam parameters in the range relevant for CLIC and comment on the implications for the design of such a machine.

TUPC009

The Recent JINR Advances in Technology Development on Linear Accelerators

laser, radiation, FEL, cryomodule

1006

G. Shirkov, N. Balalykin, A. Dudarev, E. Syresin, G.V. Trubnikov, Yu.A. Yulian
JINR, Dubna, Moscow Region, Russia
E. Khazanov
IAP/RAS, Nizhny Novgorod, Russia

JINR experts take part in a few ILC related projects including photo injector prototype, participation in design and construction of cryomodules, RND on design of a new version of superconducting niobium resonator, laser metrology, etc. Some new results of this activity as well as recent data of ILC siting investigations in the Dubna region are presented.

TUPC021

The CLIC Feasibility Demonstration in CTF3

linac, cavity, acceleration, ion

1042

P.K. Skowroński, J. Barranco, S. Bettoni, B. Constance, R. Corsini, A.E. Dabrowski, M. Divall Csatari, S. Döbert, A. Dubrovskiy, O. Kononenko, M. Olvegård, T. Persson, A. Rabiller, F. Tecker
CERN, Geneva, Switzerland
E. Adli
University of Oslo, Oslo, Norway
W. Farabolini
CEA/DSM/IRFU, France
R.L. Lillestol
NTNU, Trondheim, Norway
T. Muranaka, A. Palaia, R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden

The objective of the CLIC Test Facility CTF3 is to demonstrate the feasibility issues of the CLIC two-beam technology: the efficient generation of a very high current drive beam, used as the power source to accelerate the main beam to multi-TeV energies with gradient over 100MeV/m, stable drive beam deceleration over long distances. Results on successful beam acceleration with over 100 MeV/m energy gain are shown. Measurements of drive beam deceleration over a chain of Power Extraction Structures are presented. The achieved RF power levels, the stability of the power production and of the deceleration are discussed. Finally, we overview the remaining issues to be shown until the end of 2011.

TUPC028

Background and Energy Deposition Studies for the CLIC Post-Collision Line*

photon, simulation, radiation, positron

1060

R. Appleby, M.D. Salt
UMAN, Manchester, United Kingdom
L.C. Deacon, E. Gschwendtner
CERN, Geneva, Switzerland

The CLIC post-collision line is designed to transport the spent-beam products of collision to their respective dumps, with minimal losses and thus minimal background contributions. With nanometre spot-sizes at TeV energies, large beam-beam effects induce divergence and dispersion of the outgoing beams, with a large production cross-section of Beamstrahlung photons and subsequently coherent pairs. The post-collision line should provide sufficient divergence of the beam to avoid damage to the vacuum exit and dump entrance windows. In this study, the beam losses are investigated, with the production of secondary particles from the interaction with matter simulated. The particle flux leakage from absorbers and dumps is modelled to determine the total energy deposited on magnets of the post-collision line. Finally, both electromagnetic and hadronic backgrounds at the CLIC experiment are considered.

TUPC030

Recommendation for Mitigations of the Electron Cloud Instability in the ILC

vacuum, positron, emittance, quadrupole

1063

M.T.F. Pivi, L. Wang
SLAC, Menlo Park, California, USA
L.E. Boon, K.C. Harkay
ANL, Argonne, USA
J.A. Crittenden, G. Dugan, M.A. Palmer
CLASSE, Ithaca, New York, USA
T. Demma, S. Guiducci
INFN/LNF, Frascati (Roma), Italy
M.A. Furman
LBNL, Berkeley, California, USA
K. Ohmi, K. Shibata, Y. Suetsugu, J. Urakawa
KEK, Ibaraki, Japan
C. Yin Vallgren
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden

Funding: Work supported by the Director, Office of Science, High Energy Physics, U.S. DOE under Contract No. DE-AC02-76SF00515.
Electron cloud has been identified as one of the highest priority issues for the ILC Damping Rings (DR). A working group has evaluated the electron cloud effect and instability, and mitigation solutions for the electron cloud formation. Working group deliverables include recommendations for the baseline and alternate solutions for the electron cloud mitigation in various regions of the ILC Positron DR, which is presently assumed to be the 3.2km design. Detailed studies of a range of mitigation options including coatings, clearing electrodes, grooves and novel concepts, were carried out over the previous several years by nearly 50 researchers, and the results of the studies form the basis for the recommendation. The assessments of the benefits or risks associated with the various options were based on a systematic ranking scheme. The recommendations are the result of the working group discussions held at numerous meetings and during a dedicated workshop. The mitigation choices will be also presented in a more detailed report later in 2012. In addition, a number of items requiring further investigation were identified and studies will be carried out at CesrTA and other institutions.

TUPC031

Advanced Research Electron Accelerator Laboratory Based on Photocathode RF Gun

gun, emittance, laser, controls

1066

B. Grigoryan, G.A. Amatuni, V.S. Avagyan, A. Grigoryan, M. Ivanyan, V.G. Khachatryan, E.M. Laziev, K. Manukyan, I.N. Margaryan, V. Sahakyan, A. Sargsyan, A. Tarloyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan
CANDLE, Yerevan, Armenia
T. Vardanyan
YSU, Yerevan, Armenia

The low energy sub-picosecond duration electron bunches with extremely small beam emittance have wide applications in advanced research of new accelerator concepts, radiation physics, time-resolved pulse radiolysis and electron diffraction. The conceptual design and experimental program of the Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun are presented. The AREAL design implies single and multibunch operation modes with variable beam energy of 5-20 MeV and 10-100 pC bunch charge. The design is based on 3 GHz 1.6 cells RF gun followed by S-Band accelerating linac.

TUPC032

Beam Phase-Space Study for AREAL RF Photogun Linac

gun, emittance, space-charge, linac

1069

B. Grigoryan, G.A. Amatuni, I.N. Margaryan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan
CANDLE, Yerevan, Armenia

In order to produce high brightness electron beams with sub-picosecond bunch duration, the creation of Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun is under consideration. For several experimental setup purposes the linac will operate in single and multibunch modes with final beam energy 5-20 MeV and the bunch charge 10 100 pC. The study of beam phase space evolution along the linac is performed to optimize the beam main characteristics: emittance, bunch length and energy spread. The dependence of longitudinal and transverse distribution of electrons in photocathode region on RF cavity performances is analyzed.

TUPC033

Verifying the Single Bunch Capability of the New Injector at ELSA*

linac, gun, single-bunch, pick-up

1072

S. Mey, O. Boldt, W. Hillert, N. Hofmann, F. Klarner, D. Krönung, A. Roth, M. Schedler
ELSA, Bonn, Germany
S. Aderhold
DESY, Hamburg, Germany

Funding: Funded by the DFG within the SFB / TR 16 and the Helmholtz Alliance HA 10¹ "Physics at the Terascale".
In order to enhance the operating capabilities of the Bonn University Accelerator Facility, ELSA, a new injector is currently under commissioning. One of its main purpose is to allow a single pulse mode. The injector produces a single electron bunch with 1.5 A pulse current. Design and optimization of the injector have been performed with EGUN, PARMELA and numerical simulations based on the numerical integration of the paraxial equation. A 1 ns long pulse is produced by a thermionic electron source with 90 kV anode - cathode voltage, then compressed and pre-accelerated by a subsequent 500 MHz RF cavity and a four-cell travelling wave buncher. Finally, the bunch will be accelerated to 20 MeV by the main LINAC section. Measurements have been conducted concerning the resulting pulse length and pulse charge to confirm the predictions made by simulations and to investigate the efficiency of the injector system.

TUPC034

Design Studies on 100 MeV/100 kW Electron Linac for NSC KIPT Neutron Source on the Base of Subcritical Assembly Driven by Linac

linac, emittance, gun, target

1075

Y.L. Chi, J. Cao, X.W. Dai, C.D. Deng, M. Hou, X.C. Kong, R.L. Liu, W.B. Liu, C. Ma, G. Pei, H. Song, S.H. Wang, G. Xu, J. Zhao, Z.S. Zhou
IHEP Beijing, Beijing, People's Republic of China
M.I. Ayzatskiy, I.M. Karnaukhov, V.A. Kushnir, V.V. Mytrochenko, A.Y. Zelinsky
NSC/KIPT, Kharkov, Ukraine
S. Pei
IHEP Beijng, Beijing, People's Republic of China

In NSC KIPT, Kharkov, Ukraine, a neutron source on the base of subcritical assembly driven by 100 MeV/100 kW electron linear accelerator is under design and development. To provide neutron flux value of about 1013 neutron/s the electron linear accelerator with 100 MeV beam and average beam power of 100 kW will be used. Construction and manufacture of the linear accelerator of such high beam intensity with low emittance and beam losses is a challenging task. In the report the project of the electron linear accelerator of the required beam energy and intensity is described. The accelerator structure and main technical solutions are presented. To overcome the BBU effect of this high average beam current, several effective measures are adopt, such as using constant gradient structure to spread the HOMs frequencies different cells, larger inner radius and shorter section length make the higher group velocity and optimize the structure geometry to keep the shunt impedance as good as possible. After the beam bunching system, a chicane is followed to chopper the beam to avoid the beam lost in the higher energy part.

TUPC036

S-band ps Pulse Photoinjector for THz Radiation Source

coupling, electromagnetic-fields, gun, acceleration

1078

S.M. Polozov, T.V. Bondarenko
MEPhI, Moscow, Russia

S-band photoinjectors with ps pulse are becoming promising as e-guns for high-intensity sub-mm wavelength pulse source. Development of accelerating system for photoinjector with ps bunch is reported. The main aim is to develop a model of accelerating structure that provide top accelerating fields in respect to high electric strength and low RF power uses. The accelerating structures consisting of 1.6 cell of disk-loaded waveguide (DLW), 3 cells and 2 half-cells of DLW, 7 cels and 2 half-cells of DLW and accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW are studying. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics, electric field distribution for all models were acquired. Accelerating structure consisting of 1.6 cells will operate in pi mode of standing wave, all other structures operate in pi/2 mode traveling wave. Accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW has most suitable electrodynamics characteristics and field distribution for sub-mm pulse source according to simulation results.

TUPC038

A Low Energy Thermionic RF Gun Linac for Ultrashort Electron Beam

linac, gun, bunching, klystron

1081

J.-Y. Hwang, J.H. Chen, W.K. Lau, A.P. Lee, T.H. Wu
NSRRC, Hsinchu, Taiwan
N.Y. Huang
NTHU, Hsinchu, Taiwan

A low energy test linac is being constructed at NSRRC for technological development of high brightness electron injector. It is a 29 MeV S-band linac that equipped with a high gradient thermionic cathode rf gun for generation of ultrashort relativistic electron beam by velocity bunching in the rf linac section located at downstream. High quality GHz-repetition-rate electron pulses of about 30 pC in bunch charge, pulse duration as short as 100 fsec can be produced from this test facility. It can be used as the driver for future light source experiments such as ultrafast head-on inverse Compton scattering (ICS) X-ray source and intense coherent THz free electron lasers.

TUPC039

Proposals for Electron Beam Transportation Channel to Provide Homogeneous Beam Density Distribution at a Target Surface

target, neutron, quadrupole, beam-losses

1084

A.Y. Zelinsky, I.M. Karnaukhov
NSC/KIPT, Kharkov, Ukraine
W.B. Liu
IHEP Beijing, Beijing, People's Republic of China

NSC KIPT neutron source will use 64x64 mm rectangular tungsten or uranium target. To generate maximum neutron flux, prevent overheating of the target and reduce thermal stress one should provide homogeneous electron beam distribution at the target surface. In the facility transportation channel three different possibilities of electron beam density redistribution along the target surface can be realized. It can be the fast beam scanning with two dimensional scanning magnets; the method of uniform beam distribution formation with linear focusing elements (dipole and quadrupole magnets) and nonlinear focusing elements (octupole magnets), when final required rectangular beam shape with homogeneous beam density is formed at target; and combined method, when one forms the small rectangular beam with homogeneous beam density distribution and scan it over the target surface with scanning magnets. In the report the all tree methods are considered and discussed considering the layout of the NSC KIPT transportation channel. Calculation results show that the proposed transportation channel lattice can provide uniform beam of rectangular shape with sizes 64x64 mm without target overheating.

TUPC040

Modified Lattice of the Compton X-ray Source NESTOR

lattice, storage-ring, sextupole, focusing

1087

A.Y. Zelinsky, P. Gladkikh, A.A. Kalamayko, I.M. Karnaukhov, A. Mytsykov, A.A. Shcherbakov
NSC/KIPT, Kharkov, Ukraine

NESTOR is Compton X-ray source that is under commissioning in NSC KIPT. One of the main parts of the facility is the middle energy storage ring (40-225 MeV). The storage ring has comprehensive lattice to provide low emittance, low beam size in the interaction point and big value of the energy acceptance. One of the NESTOR storage ring lattice feature is use of bending magnets of 0.5 m radius with combined focusing function. It leads to increasing of 3D magnetic field effects on electron beam dynamics. After NESTOR magnetic element manufacturing characteristics of element magnetic fields were measured and the effect of the real magnetic field distribution on beam dynamics was calculated. As a result, to provide project X-ray source characteristics the parameters of NESTOR storage ring lattice should be modified. The second reason for the lattice modification was the desire to increase the interaction point straight section length. The results of the beam dynamics simulation after lattice modification and optimization show that the storage ring will provide all project electron beam parameters. The results of the electron beam simulations are presented in the paper.

TUPC041

Self-consistent Time-dependent Quasi-3D Model of Multipactor in Dielectric-loaded Accelerating Structures

space-charge, vacuum, multipactoring, plasma

1090

O.V. Sinitsyn, T.M. Antonsen, G.S. Nusinovich
UMD, College Park, Maryland, USA

Funding: This work is supported by the Office of High Energy Physics of the US Department of Energy.
Multipactor (MP) manifests itself as a rapid growth of the number of secondary electrons emitted from a solid surface in the presence of the RF field under vacuum conditions. The secondary electrons appear as the result of surface impacts of energetic primary electrons accelerated by the RF field. MP occurs in various microwave and RF systems and usually severely degrades their performance. Therefore, theoretical and experimental studies of MP are of great interest to researchers working in related areas of physics and engineering. In this paper we study MP in dielectric-loaded accelerating (DLA) structures. We started our work with the development of a self-consistent time-dependent 2D model of MP in such structures*. To benchmark that model, we compared its results with available experimental data**. The comparison showed good agreement between theory and experiment for DLA structures of larger diameter, however for structures of smaller diameter a significant discrepancy was observed. Therefore, we decided to develop a new quasi-3D model of MP that would allow us to take into account the effects ignored in our 2D studies. Results of our 3D analysis are presented in this paper.
* O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., Phys. Plasmas, 16, 073102 (2009).
** O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., AIP Conf. Proc., 1299, 302 (2010).

TUPC042

First Beam to FACET

linac, positron, controls, vacuum

1093

R.A. Erickson, C.I. Clarke, W.S. Colocho, F.-J. Decker, M.J. Hogan, S. Kalsi, N. Lipkowitz, J. Nelson, N. Phinney, P. Schuh, J. Sheppard, H. Smith, T.J. Smith, M. Stanek, J.L. Turner, J. Warren, S.P. Weathersby, U. Wienands, W. Wittmer, M. Woodley, G. Yocky
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Department of Energy contract DE-AC02-76SF00515.
The SLAC 3km linear electron accelerator has been reconfigured to provide a beam of electrons to the new FACET facility while simultaneously providing an electron beam to the Linac Coherent Light Source (LCLS). FACET is a new experimental facility constructed in the linac tunnel that can transport, compress, and focus electron bunches to support a variety of accelerator R&D experiments. In this paper, we describe our first experiences with the operation of the linac for this new facility.

TUPC043

SEM Field Emission Probe Surface Science Study

cathode, vacuum, gun, laser

1096

L. Laurent, R.E. Kirby, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work is supported by Department of Energy Contract No. DE-AC03- 76SF00515.
After decades of rf breakdown research, a common acknowledgement among researchers is that a better understanding of what is happening on the surface at a microscopic level needs to be the impetus for future studies. We are designing and fabricating an electron microscope-based high-electric-field current-emission probe to study topographic material features which will enable us to better understand and further advance the technology of high-brightness photocathode rf guns and enable the study of high gradient phenomena. The SEM field emission probe will provide an important diagnostic tool allowing cathodes and high gradient surfaces to be evaluated before and after testing and will help identify and understand the relationship between high field emission locations and vacuum breakdown, non-uniform emission, surface cracking, hotspots, etc. The preliminary results and 2012 goals will be presented.

TUPC045

Recirculating Electron Linacs (REL) for LHeC and eRHIC

linac, lattice, dipole, proton

1099

D. Trbojevic, J. Beebe-Wang, Y. Hao, D. Kayran, V. Litvinenko, V. Ptitsyn, N. Tsoupas
BNL, Upton, Long Island, New York, USA

Funding: Work performed under a Contract Number DE-AC02-98CH10886 with the auspices of the US Department of Energy.
We present a design of a CW Electron Recovery Linacs (ERL) for future electron hadron colliders eRHIC and LHeC. In eRHIC, a six-pass ERL would be installed in the existing tunnel of the present Relativistic Heavy Ion Collider (RHIC). The 5-30 GeV polarized electrons will collide with RHIC’s 50-250 (325) GeV polarized protons or 20-100 (130) GeV/u heavy ions. In LHeC a 3-pass 60 GeV CW ERL will produce polarized electrons for collisions with 7 TeV protons. After collision, electron beam energy is recovered and electrons are dumped at low energy. Two superconducting linacs are located in the two straight sections in both ERLs. The multiple arcs are made of Flexible Momentum Compaction lattice (FMC) allowing adjustable momentum compaction for electrons with different energies. The multiple arcs, placed above each other, are matched to the two linac’s straight sections with splitters and combiners.

TUPC055

Strongly Space Charge Dominated Beam Transport at 50 keV

solenoid, beam-transport, simulation, space-charge

1123

D. Heiliger, W. Hillert, B. Neff
ELSA, Bonn, Germany

Funding: supported by DFG (SFB/TR16)
A pulsed (100 nC in 1 us), low energetic beam of polarized electrons is routinely provided by an inverted source of polarized electrons at ELSA. The beam transport to the linear accelerator is strongly space charge dominated due to the beam energy of 50 keV. Thus, the actual beam current has an impact on the beam dynamics, and the optics of the transfer line to the linear accelerator must be optimized with respect to the chosen beam intensity. Numerical simulations of the beam transport demonstrate that an intensity upgrade from 100 mA to 200 mA is feasible. In order to successfully adjust the focussing strength of the magnets according to the final results of the simulation, dedicated beam diagnostics like wire scanners suitable for extreme-high vacuum applications are required.

TUPC057

Femtosecond Photoinjector and Relativistic Electron Microscopy

gun, emittance, laser, cathode

1126

J. Yang, K. Kan, Y. Murooka, N. Naruse, K. Tanimura, Y. Yoshida
ISIR, Osaka, Japan
J. Urakawa
KEK, Ibaraki, Japan

A new rf gun driven by a femtosecond laser has been developed successfully for the relativistic electron diffraction in Osaka University for the study of ultrafast dynamics of intricate molecular and atomic processes in materials. The beam dynamics of femtosecond electron bunch in the rf gun were investigated to achieve a low-emittance and low-energy-spread; i.e. 0.1 mm-mrad and 10^-4. A time-resolved relativistic electron microscopy is being developed to reveal the hidden dynamics on the femtosecond and nanometer scales. The same demonstrations of the MeV electron diffraction/imaging measurements were reported.

TUPC058

Design of a Chirping Cell Attached RF Gun for Ultrashort Electron Generation

gun, cavity, laser, radiation

1129

K. Sakaue, K. Tamai, M. Washio
RISE, Tokyo, Japan
J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690
We have been developing an S-band photocathode rf electron gun at Waseda university. Our rf-gun cavity was firstly designed by BNL and then, modified by our group. In this paper, we will introduce a newly designed rf-gun cavity with energy chirping cell. To generate an energy chirped electron bunch, we attached extra-cell for 1.6cell rf-gun cavity. Cavity design was done by Superfish and particle tracing by PARMELA. By optimizing the chirping cell, we observed linear chirped electron bunch. The front electron have lower energy than rear. Then transporting about 2m, the bunch can be compressed down to 200fsec electron bunch with the charge of 160pC. This ultrashort bunch will be able to use for generating CSR THz radiation, pumping some material to be studied by pulse radiolysis method, and so on. In this conference, the design of chirping cell attached rf-gun, the results of tracing simulation and plan of manufacturing will be presented.

TUPC059

Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun

laser, beam-loading, cavity, gun

1132

Y. Yokoyama, T. Aoki, K. Sakaue, T. Suzuki, M. Washio, T. Yamamoto
RISE, Tokyo, Japan
H. Hayano, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program.
At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans.

TUPC060

A Multi-mode RF Photocathode Gun

gun, cathode, cavity, injection

1135

S.V. Kuzikov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia
J.L. Hirshfield
Yale University, Physics Department, New Haven, CT, USA
Y. Jiang
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
V. Vogel
DESY, Hamburg, Germany

A photocathode injection gun based on standard emittance compensating techniques and driven by several (N ≥ 2) harmonically related RF sources is considered. Multi-harmonic excitation can provide high-quality flatness in time of the field at the cathode when a bunch is being injected. This allows one to obtain ≥1 nC, 20-40 ps electron bunches with preservation of low emittance. Another advantage is a reduction of Ohmic losses and the required input RF power (for a given cathode field). Preliminary calculations show that input power in a three-mode cavity (0.65 GHz, 1.3 GHz, 2.6 GHz) is nearly half the power needed to feed a single mode with the same cathode field. A further appealing property is the predicted increase of breakdown threshold due to a reduction of surface exposure time to high fields in a symmetric cavity, and due to the so-called anode-cathode effect in a longitudinally asymmetric cavity. These properties may help one to reach bunch energies as high as 3-5 MeV after the first half cell.

TUPC062

Electron Beam Energy Measurement at the Australian Synchrotron Storage Ring

storage-ring, synchrotron, resonance, scattering

1138

M.J. Boland
ASCo, Clayton, Victoria, Australia
H. Panopoulos, R.P. Rassool, K.P. Wootton
The University of Melbourne, Melbourne, Australia

The technique of resonant spin depolarization was used to precisely measure the electron beam energy in the storage ring at the Australian Synchrotron. A detector and data acquisition system dedicated to the measurement were developed. Using the system, the long term energy stability of the storage ring was monitored and a mechanical realignment of the ring was clearly seen in the energy data. Details of the parameters used to optimize the measurement are also discussed.

TUPC069

Bunch Length Measurements from the Incoherent Synchrotron Radiation Fluctuation at SOLEIL

radiation, undulator, optics, photon

1159

M.-A. Tordeux, F. Dohou, M. Labat, O. Marcouillé
SOLEIL, Gif-sur-Yvette, France

Bunch length measurements can be made by analysing the pulse to pulse intensity fluctuation of the incoherent synchrotron radiation as it has been reported elsewhere*. Such a method has been tested at SOLEIL for picosecond bunch durations, at several wavelengths and bandwidths in the visible range, using an avalanche photodiode. Thanks to the low-alpha optics the lengths of 10 μA bunches as short as 3 ps have been measured in good agreement with the streak camera results. We first used the radiation from a bending magnet, and then from a HU640 undulator that enhances the photon flux. Moreover, taking advantage of using the radiation from an undulator, we show that the method can still be used when the number of spikes emitted by the electron bunch is reduced to a few hundreds. This could be of interest for bunch length measurements of X-ray SASE FELs. Furthermore, we intend to use a single crystal diamond detector in order to perform these measurements in the X-ray range.
* F. Sannibale et al., "Absolute bunch length measurements by incoherent radiation fluctuation analysis", PRST AB 12, 032801 (2009).

TUPC072

Accurate Electron Beam Size Measurement at the Metrology Light Source

photon, radiation, polarization, storage-ring

1165

R. Klein, G. Brandt, R. Thornagel
PTB, Berlin, Germany
J. Feikes, M. Ries, G. Wüstefeld
HZB, Berlin, Germany

For the operation of the Metrology Light Source (MLS)*, the dedicated electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB), as the national primary radiation source standard from the near infrared to the vacuum ultraviolet spectral region, all storage ring parameters which are relevant for the calculation of the radiant intensity by the Schwinger equation have to be known absolutely with small uncertainties. For the measurement of the effective vertical electron beam size a Bragg polarimeter, operating at a photon energy of 1103 eV, has been designed and put into operation. This system also serves as a detection system for the image of the electron beam through a set of narrow slits. The results obtained with the new device are compared to those measured by an optical beam imaging system**.
* R. Klein et al., Phys. Rev. ST-AB 11, 110701 (2008).
** C. Koschitzki et al., Proc. IPAC10, 894-896 (2010).

TUPC074

A New Counting Silicon Strip Detector System for Precise Compton Polarimetry

polarization, photon, laser, scattering

1171

R. Zimmermann, W. Hillert, J.C. Wittschen
ELSA, Bonn, Germany

Funding: Supported by the German Research Foundation within the SFB/TR16
A Compton polarimeter is currently being installed at the Electron Stretcher Facility ELSA to monitor the degree of polarization of the stored electron beam. For this purpose, circularly polarized light that is emitted by a laser and backscattered off the beam has to be detected. Above all, as a result of ELSA's beam energies, it is necessary to measure the shift of the center of the photon spatial distribution which is obtained when the polarization of the laser is switched from left-hand to right-hand circular polarization with an accuracy of a few microns. In order to meet the required specifications, a new counting silicon strip detector system has been developed in cooperation with the SiLab/ATLAS group of the Physics Institute of the University of Bonn. In this contribution, the design of the system will be presented and first results will be shown.

TUPC076

Realization of a High Bandwidth Bunch Arrival-time Monitor with Cone-shaped Pickup Electrodes for FLASH and XFEL

pick-up, laser, coupling, free-electron-laser

1177

A. Angelovski, M. Hansli, R. Jakoby, A. Kuhl, A. Penirschke, S. Schnepp
TU Darmstadt, Darmstadt, Germany
M. Bousonville, H. Schlarb
DESY, Hamburg, Germany
T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Funded by the Federal Ministry of Education and Research (BMBF): 05K10RDA
In the Free Electron Laser in Hamburg (FLASH) an electro-optical system is used as a Bunch Arrival time Monitor (BAM). The time-of-arrival resolution is proportional to the steepness of the beam pick-up signal at the first zero-crossing*. Future experiments will be conducted using significantly lower bunch charges resulting in a reduced signal steepness. This requires BAM pickup electrodes with increased bandwidth as introduced in **. This paper presents the implementation and measurement results of a high bandwidth cone-shaped pickup capable of operating in the frequency range up to 40 GHz. The slope steepness at the zero crossing is investigated for a simplified equivalent circuit model. RF-measurements have been performed using a non-hermetic prototype of the BAM pickups for assessing the influence of manufacturing tolerances on the sensor performance. The measurements are compared to simulation results obtained by CST PARTICLE STUDIO®.
* F. Loehl et al., Proc. of DIPAC2007, WEPB15, p. 262 (2007).
** A. Angelovski et al., "Pickup design for a high resolution Bunch Arrival time Monitor for FLASH and XFEL", DIPAC2011.

TUPC079

Sensitivity and Tolerance Analysis of a New Bunch Arrival-time Monitor Pickup Design for FLASH and XFEL

pick-up, simulation, laser, free-electron-laser

1186

A. Kuhl, A. Angelovski, R. Jakoby, A. Penirschke, S. Schnepp
TU Darmstadt, Darmstadt, Germany
M. Bousonville, H. Schlarb
DESY, Hamburg, Germany
T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Supported by the Graduate School of Computational Engineering at TU Darmstadt and the Federal Ministry of Education and Research (BMBF): 05K10RDA "Weiterentwickung eines Ankunftszeitmonitors"
The Free Electron Laser in Hamburg (FLASH) is equipped with Bunch Arrival Time Monitors (BAM)*, which provide for a time resolution of less than 10 fs for bunch charges higher than 0.2 nC. Future experiments, however, will aim at generating FEL light pulses from a broad range of bunch charges down to 10 pC. In these circumstances the requirements on the time resolution will no longer be fulfilled, which demands for a larger bandwidth of the pickup system. A new cone-shaped pickup, which has a bandwidth greater than 40 GHz has been proposed**. At high frequencies, small manufacturing tolerances might have great influence on the pickup signal. A sensitivity analysis of several manufacturing tolerances in the pickup design regarding their influence on the output signal was carried out (by means of CST PARTICLE STUDIO®). These results are utilized for setting limits to the manufacturing tolerances.
* M.K. Bock et al., IPAC2010, WEOCMH02, Kyoto, Japan, 2010.
** A. Kuhl et al., "Design eines hochauflösenden Ankunftszeitmonitor für FLASH", DPG Frühjahrstagung 2011, Karlsruhe, Germany.

TUPC081

Diagnostics of Femtosecond Low-charge Electron Bunches at REGAE

photon, diagnostics, laser, simulation

1192

S. Bayesteh
Uni HH, Hamburg, Germany
H. Delsim-Hashemi
DESY, Hamburg, Germany

A new linac is constructed at DESY as the electron source fo "Relativistic Electron Gun for Atomic Exploration (REGAE)". REGAE is mainly established for a Femtosecond electron diffraction experiment presenting structural information on atomic transition states occurring in the sub-hundred femtosecond time-scale. REGAE comprises a photo-cathode gun followed by normal conducting 1.5 cell RF cavity to provide sub pico-Coulomb charge of 2 to 5 MeV energy with a coherent length in the range of 30nm. In order to produce and maintain such high quality electron bunches, sophisticated single-shot diagnostics is mandatory to monitor the properties. Diagnostics include emittance, energy, energy spread and bunch length measurement. In this paper the conceptual ideas and steps toward realization of these diagnostics are presented with a detailed focus on transverse diagnostics. As for photon source of transversal diagnostics, scintillators are studied. Simulation results show which material suits the best for REGAE parameters. Layout of a home-made intensified camera is presented. The method discussed in this paper would also be advantageous for low-charge Free Electron Lasers.

TUPC082

Beam Current Measurements at the TSR Heidelberg

ion, pick-up, acceleration, storage-ring

1195

M. Grieser, S.T. Artikova, K. Blaum, F. Laux, J. Ullrich
MPI-K, Heidelberg, Germany

To conduct experiments using low energy ion beams at the TSR heavy ion storage ring, the beam deceleration process must be well understood. During deceleration of the beam the revolution frequency decreases, resulting in low current, which is difficult to measure with a common DC transformer. The number of particles in a bunch is determined by measuring the voltage signal in the time domain using a capacitive pick-up. If the ratio of bunch length and RF period does not change during the deceleration or acceleration, measuring the pick-up signal spectrum, where the signal is directly proportional to the number of particles in a bunch, is a more sensitive method. An alternative method is using a beam profile monitor (BPM) for determining the number of particles in the storage ring via ionization rate measurements of the residual gas. A summary of these different methods to determine the number of particles is presented.

TUPC083

Comparative Studies into 3D Beam Loss Simulations

simulation, photon, beam-losses, positron

1198

M. Panniello
MPI-K, Heidelberg, Germany
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Work supported by the Helmholtz Association and GSI under contract VH-NG-328.
A detailed understanding and monitoring of potential beam loss mechanisms is crucial for every particle accelerator. The main motivation in low energy facilities, such as the Ultra-low energy Storage Ring (USR) at the future Facility of Low energy Antiproton and Ion Research (FLAIR), comes from the very low number of particles available which in such machine ought to be conserved. In High Energy accelerators it is the concern about activation or even physical damage of machine parts which has to be taken into serious account. The CLIC Test Facility (CTF3) at CERN provides an ideal testing ground for studies into novel BLM systems and is well suited for benchmarking the results from numerical simulations in experiments. This contribution summarizes the three-dimensional beam loss pattern as found with the commonly used codes FLUKA and Géant4. The results from these codes are compared and analyzed in detail and used for the identification of optimum beam loss monitor locations.

TUPC084

Performance of the Scintillation Profile Monitor in the COSY Synchrotron

vacuum, synchrotron, proton, target

1201

V. Kamerdzhiev, J. Dietrich, K. Reimers
FZJ, Jülich, Germany

Residual gas scintillation is used for measuring profile of the proton beam circulating in the COSY synchrotron. The problem of low rate of scintillation events detected by a multichannel photomultiplier is coped with by injecting small amounts of pure nitrogen into the SPM vacuum chamber. This leads to a temporary local pressure bump of no more than an order of magnitude. A commercially available piezo-electric dosing valve allows good control over the amplitude and duration of the pressure bump. Since the average pressure in the machine is hardly changed, the method is fully compatible with experiment operation. This approach offers a robust and inexpensive way to measure the beam profile. The design of the SPM is discussed. The latest measurement results and comparison to the ionization profile monitor data is presented.

TUPC086

A Setup for Single Shot Electro Optical Bunch Length Measurements at the ANKA Storage Ring

laser, storage-ring, synchrotron, radiation

1206

N. Hiller, E. Huttel, A.-S. Müller, A. Plech
KIT, Karlsruhe, Germany
F. Müller, P. Peier, V. Schlott
PSI, Villigen, Switzerland

Funding: Supported by the Initiative and Networking Fund of the Helmholtz Association under VH-NG-320. Sponsored by the German Federal Ministry of Education and Research under contract number 05K10VKC
Single shot electro optical bunch length measurements, in particular using spectral decoding, are foreseen for the ANKA storage ring. This will allow to resolve fast changes of bunch deformation and structure during the low alpha operation (2-15 ps rms bunch length). This technique uses a chirped laser pulse to probe the field induced birefringence in an electro optical crystal. The laser pulse is then analyzed in a single shot spectrometer. To obtain the birefringence modulation one can either use the near field of the electron bunch (placing the crystal close to the electron bunch in the UHV system of the storage ring), or the far field (coherent synchrotron radiation in the THz range at a THz-/IR-Beamline). The laser needs to supply: sufficient tunability of pulse length, a wide spectrum to allow for a sub-ps resolution. Additionally it must provide a mode-locked operation synchronized to the bunch revolution clock. For this purpose, a mode locked Ytterbium fibre laser system which operates at 10³⁰ nm has been developed at the Paul-Scherrer Institute in Switzerland. We give an overview over the experimental set up in the ANKA storage ring and the status of the project.

TUPC087

Filling Pattern Measurements at the ANKA Storage Ring

photon, storage-ring, single-bunch, synchrotron

1209

B. Kehrer, N. Hiller, A. Hofmann, E. Huttel, V. Judin, M. Klein, S. Marsching, A.-S. Müller, N.J. Smale
KIT, Karlsruhe, Germany

For many accelerator physics studies, e.g. the investigation of coherent synchrotron radiation (CSR), a precise knowledge of the quantitative filling pattern (i.e. the number of electrons per bunch) is essential. This can be achieved by either using a linear detector (analog recording) or by employing the method of time-correlated single photon counting (TCSPC). At the ANKA storage ring both methods are in use. The analogue detection is based on the signal from a stripline or annular electrode, the TCSPC uses a Single Photon Avalanche Diode (SPAD). In this paper, we describe the experimental set-ups and present results of a comparison of the two techniques for single as well as for multi bunch filling patterns.

TUPC088

An Ionization Profile Monitor for the Determination of the FLASH and PITZ Beam Parameters

photon, vacuum, diagnostics, ion

1212

J. Mießner, H.-J. Grabosch, M. Markert, R. Sternberger
DESY Zeuthen, Zeuthen, Germany
A. Hofmann
KIT, Karlsruhe, Germany
K.I. Tiedtke
DESY, Hamburg, Germany

To operate FLASH (Free-electron LASer at Hamburg) successfully, accurate measurements of the photon beam parameters, like position and profile, are essential. The development of a specific Ionization Profile Monitor (IPM) is one contribution to the photon beam diagnostics, and currently one horizontal and one vertical oriented IPM are installed at FLASH. The working principle of the IPM is based on the detection of ions generated by interactions of the photon beam with the residual gas, which is always present in the beam line. An essential advantage of this method is that the beam is not influenced by the IPM, so it is possible to analyze the beam parameters without beam destruction. Moreover, the monitor is able to determine the relative position and the spatial profile of the beam with the precision of a few um. In this poster, the design and first measurements with the IPM taken at FLASH are presented. A good measuring accuracy of the IPM is obtained. Moreover, first results of measurements at PITZ (PhotoInjector Testfacility at Zeuthen) are given for one vertical oriented IPM with a up to 25 MeV electron beam.

TUPC091

Operational Results of the Diamond-based Halo Monitor during Commissioning of SPring-8 XFEL (SACLA)

undulator, laser, wakefield, scattering

1218

H. Aoyagi
JASRI/SPring-8, Hyogo-ken, Japan
Y. Asano, H. Kitamura, T. Tanaka
RIKEN/SPring-8, Hyogo, Japan

Funding: This work is partly supported by Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (c) 21604017.
Measurement of electron beam halo is very important issue for X-ray free electron laser and synchrotron radiation facilities, because the beam halo may cause radiation damage of undulator magnets. Furthermore, it may cause degradation in quality of electron beam, and radio activation of beam ducts and components. In order to prevent these situations, a diamond-based halo monitor (HM) has been developed for the SPring-8 Angstrom Compact free electron LAser (SACLA). We have achieved excellent detection limit of 0.3 fC/pulse for single-shot measurement, which corresponds to the ratio of 10^-6 to the beam core. The commissioning of the HM, which was installed at the upstream of 90m undulator, has been carried out, and it has been figured out that the intensity of the beam halo can be measured very nicely since secondary electrons and bremsstrahlung that are emitted in the accelerator components have not been observed. We also describe systematic profile measurements of the beam halo and operational results of the HM during the commissioning of SACLA.

TUPC093

CSR Bunch Length Monitor for XFEL/SPring-8 - SACLA

radiation, FEL, synchrotron, synchrotron-radiation

1224

C. Kondo, S. Matsubara, T. Matsumoto
JASRI/SPring-8, Hyogo-ken, Japan
S.I. Inoue, H. Maesaka, Y. Otake
RIKEN Spring-8 Harima, Hyogo, Japan

SPring-8 Angstrom Compact Free Electron Laser (SACLA) is now under commissioning operation, aimed at the generation of a sub-angstrom free electron laser (FEL). In order to ensure the stable FEL generation, non-distractive bunch length monitors utilizing coherent synchrotron radiation (CSR) are installed. The monitors are located at the downstream of individual bunch compressor (BC1-BC3), and they measure the radiation emitted at the individual last magnets of the chicanes. At the magnets, beams with bunch lengths form 10 fs to 1000 fs generate the CSRs with a spectrum ranging the almost whole infrared region (0.03 - 3 THz). The CSRs are detected by a Schottky diode at the BC1, or pyroelectric detectors and a simple organic lens optical system at BC2 and 3. The bunch length monitor systems are used for bunch length feedback control to obtain the stable lasing by changing the rf parameter of acceleration cavities before the BCs. A preliminary system for the above mentioned system was tested at the SCSS test accelerator, and it showed sufficient performance to measure bunch length up to 300 fs. In this report, we describe the design and the results of the first operation.

TUPC094

Development of High-speed Differential Current-transformer Monitor

bunching, gun, monitoring, status

1227

S. Matsubara, H. Ego, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan
A. Higashiya, S.I. Inoue, Y. Otake
RIKEN/SPring-8, Hyogo, Japan
H. Maesaka
RIKEN Spring-8 Harima, Hyogo, Japan

The XFEL, which was named SACLA, was constructed in the SPring-8 site. In the SACLA, the bunch length of an electron beam is compressed from 1 ns to 30 fs, and the beam charge is decreased to obtain a genuine electron beam from 1nC to 0.3 nC for lasing. A new current-transformer (CT) monitor, which should measure the charge of the electron beam and make bunch length observation in velocity bunching process, was developed with two advantageous properties. One is differential output signal which suppresses common-mode noise from the thyratron of a klystron modulator by a factor of ten. Another property is high-speed signal output which provides a possibility to measure the bunch length and the time-of-flight (TOF) at the injector part of the SACLA. The output signal has 200 ps rise-time and a pulse width of 400 ps (FWHM) for an impulse beam. We successfully observed the bunch length between 1 ns and 400 ps around a 238 MHz buncher cavity. Moreover, we measured the TOF between two CTs with a few picoseconds resolution for a low-energy beam around 1 MeV. Thus, the new CT performance was confirmed to be sufficient for the SACLA.

TUPC101

Generation of Multimode Quasi-monochromatic Terahertz

linac, radiation, gun, cathode

1248

K. Kan, T. Kondoh, K. Norizawa, A. Ogata, J. Yang, Y. Yoshida
ISIR, Osaka, Japan

Generation of quasi-monochromatic terahertz (THz) using multimode Coherent Cherenkov Radiation (CCR) on the order of 0.1 THz was investigated. CCR was generated by a hollow dielectric tube covered by a metal and an electron bunch from a photocathode radio-frequency (RF) gun linac. The intensity and frequency of CCR were measured directly by a Michelson interferometer and a bolometer. The frequency spectra measured by the interferometer indicated sharp peaks close to frequencies of 0.09 THz and 0.14 THz, which corresponded to TM03 and TM04 modes, respectively, according to theoretical calculation for a tube with inner and outer radii of 5 mm and 7 mm. The maximum gain of TM03 mode due to the tube length was obtained as 1.5 dB/cm. The other higher modes, e. g. 0.36 THz (TM09) and 0.40 THz (TM010), were also observed from a 150 mm long tube at a bunch charge of 15 pC, which decreased space charge effect and the bunch length. Finally, a new method for bunch diagnostic based on multimode CCR was proposed. The bunch length was estimated to be 0.45 ps at a bunch charge of 5 pC with the intensity ratio of TM03 to TM09 mode.

TUPC109

Electron Bunch Slice Emittance Measurement with the Space Charge Effects*

solenoid, emittance, space-charge, simulation

1272

C. Li, Y.-C. Du, W.-H. Huang, C.-X. Tang, L.X. Yan
TUB, Beijing, People's Republic of China

Funding: supported by the National Natural Science Foundation of China (Grant Nos. 10735050, 10805031, 10875070 and 10925523), and the National Basic Research Program of China (Grant No. 2007CB815102).
Since slice transverse emittance of the electron beam is critical to a high-gain short-wavelength FEL, its characterization is very important. For space charge dominated electron beam, conventional emittance measurement techniques, such as solenoid scanning and quadruple scanning, without considering space charge forces lead to large errors of emittance evaluations. This essay introduces a modified solenoid-scan method of slice emittance measurement for space charge dominated beam, and simulations show that the new method brings the emittance evaluations much closer to actual values.

TUPC124

Laser Wire Emittance Measurement Line at CLIC*

laser, emittance, photon, collider

1308

H. Garcia, Yu.A. Kubyshin
UPC, Barcelona, Spain
T. Aumeyr, G.A. Blair
JAI, Egham, Surrey, United Kingdom
D. Schulte, F. Stulle
CERN, Geneva, Switzerland

A precise measurement of the transverse beam size and beam emittances upstream of the final focus is essential for ensuring the full luminosity at future linear colliders. A scheme for the emittance measurements at the RTML line of the CLIC using laser-wire beam profile monitors is described. A lattice of the measurement line is discussed and results of simulations of statistical and machine-related errors and of their impact on the accuracy of the emittance reconstruction are given. Modes of operation of the laser wire system and its main characteristics are discussed.

TUPC129

A Beam Position System for Hadrontherapy Facilities

photon, controls, vacuum, proton

1323

A. Faus-Golfe, C. Belver-Aguilar, C. Blanch Gutierrez, J.J. García-Garrigós
IFIC, Valencia, Spain
E. Benveniste, M. Haguenauer, P. Poilleux
LLR, Palaiseau, France

Funding: MICINN-FPA:AIC10-D-000518
Essential parts of the needed instrumentation for the beam control in the Hadrontherapy accelerators are the Beam Position Monitors (BPM). The measurement of the beam position in Hadronterapy accelerators become more important at the secondary transport lines towards the patient room where this parameter must be completely determined. The BPM described in this paper is a new type of BPM based on four scintillating fibers coupled to four photodiodes to detect the light produced by the fibers when intercepting the beam. We present here the study of the different photodiodes able to read the light emitted by the scintillating fiber, the tests performed in order to find the most suitable photodiode to measure the beam position from the variations in the beam current, the mechanical design and the corresponding acquisition electronics.

TUPC132

Imaging of the MAX III Electron Beam Profile Using Visible Synchrotron Radiation

emittance, diagnostics, synchrotron, lattice

1332

A. Hansson, Å. Andersson, E.J. Wallén
MAX-lab, Lund, Sweden

The recently assembled MAX III diagnostic beam line utilizes the bending magnet synchrotron radiation (SR) in the visible to ultraviolet range to form images of the transverse electron beam profile. Computer simulations model the generation and propagation of the SR through the beam line, taking into account effects such as diffraction, the longitudinally distributed source point and the curvature of the electron orbit. Using the diagnostic beam line, the electron beam size and the emittance in the MAX III synchrotron light source has been determined.

TUPC133

Instrumentation for the 12 GHz Stand-alone Test-stand to Test CLIC Acceleration Structures

vacuum, laser, diagnostics, ion

1335

M. Jacewicz, R.J.M.Y. Ruber, V.G. Ziemann
Uppsala University, Uppsala, Sweden
J.W. Kovermann
CERN, Geneva, Switzerland

Vacuum breakdown is one of the primary limitations in the design and construction of high energy accelerators operating with warm accelerating structures (ACS) such as CLIC linear collider because the mechanisms that cause the breakdown are still a mystery. The ongoing experimental work is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the observed discharges. The CLIC collaboration is preparing a dedicated 12 GHz test-stand to observe the characteristics of the RF discharges and their eroding effects on the ACS. The instrumentation for the test-stand must be versatile and allow for the conditioning of the ACS with measurements of the breakdown rates at different power levels as well as detection of the dark current and light emission directly relevant to breakdown physics. For that purpose we are developing 2 novel instruments. A pepper-pot chamber with an external magnetic spectrometer for measurement of the spatial and energy distributions of the electrons emitted from the ACS and an optical laser system for probing the ACS to observe the effect of a discharge on the transmitted light.

TUPC135

Beam Loss Monitors Comparison at the CERN Proton Synchrotron

beam-losses, injection, radiation, proton

1341

S.S. Gilardoni, S. Aumon, E. Effinger, J. Gil Flores
CERN, Geneva, Switzerland
U. Wienands
SLAC, Menlo Park, California, USA

CERN is planning the renovation and upgrade of the beam loss detection system for the Proton Synchrotron (PS). Improved performance in speed–to be able to monitor beam loss on a bunch-by-bunch basis–and in long-term stability–to reduce or avoid the need for periodic calibration–are aimed for. To select the most suitable technology, different detectors were benchmarked in the machine with respect to the same beam loss. The characteristics of the different detectors, the results of the measurement campaign and their suitability as future monitors for the PS are presented.

TUPC142

The Particle Identification System for the MICE Beamline Characterization

emittance, beam-losses, laser, solenoid

1356

M. Bonesini
INFN MIB, MILANO, Italy
Y. Karadzhov
DPNC, Genève, Switzerland

The International Muon Ionization Cooling Experiment (MICE) will carry out a systematic investigation of a ionization cooling section of a muon beam, for the future Neutrino Factory and the future Muon Collider. As the emittance measurement will be done on a particle-by-particle basis, a sophisticated beam instrumentation is needed to measure both particle coordinates and timing vs RF in a harsh environment due to high particle rates, fringe magnetic fields and RF backgrounds. A PID system, based on three time-of-flight stations (with resolutions up to 50-60 ps), two Aerogel Cerenkov counters and a KLOE-like calorimeter (KL) has been constructed and has allowed the commissioning of the MICE muon beamline in 2010. It will be complemented in 2011 by an Electron Muon Ranger to determine the muon range at the downstream end of the cooling section. Detector performances, as obtained in the 2010 run, will be shown and the use of PD detectors for the beamline characterization, including a preliminary measure of emittance, fully illustrated.

TUPC144

Preliminary BPM Electrics Testing for the Taiwan Photon Source Project

injection, brilliance, controls, feedback

1362

C.H. Kuo, J. Chen, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.-Y. Liao
NSRRC, Hsinchu, Taiwan

The preliminary BPM electrics are developing and testing for Taiwan Photon Source (TPS), is a 3 GeV synchrotron light source which being in construction at NSRRC. This new BPM electronics with integrated FPGA based hardware, and will be testing in the TLS (Taiwan Light Source) with real beam at first. The enhance functionality of current generation will be adopted in the TPS. The electronic prototype testing and relative property will be reported in this report.

TUPC151

Cherenkov Fibre Optic Beam Loss Monitor at ALICE

beam-losses, photon, laser, monitoring

1383

A. Intermite
The University of Liverpool, Liverpool, United Kingdom
A. Intermite, M. Putignano, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The need for real-time monitoring of beam losses, including evaluation of their intensity and the localization of their exact position, together with the possibility to overcome the limitations due to the reduced space for the diagnostics, makes optical fibres (using the Cherenkov Effect) one of the most suitable and explored candidate for beam loss monitoring. In this contribution, we report on an optical fibre beam loss monitor based on large numerical aperture pure silicon fibres and silicon photomultipliers, tested at ALICE, Daresbury Laboratories, UK. The original design of the sensor has the advantage to combine the functions of a real time detector and a transmission line. It also allows reading the signals independently and determining the time and position of the losses without the use of an external trigger.

TUPC152

Comparative Study of Performance of Silicon Photomultipliers for Use in Cherenkov Fibre Optic Beam Loss Monitors

photon, beam-losses, monitoring, lattice

1386

A. Intermite
The University of Liverpool, Liverpool, United Kingdom
A. Intermite, M. Putignano, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Silicon Photomultipliers (SiPMs) are semiconductor photo-sensitive devices built from a matrix of Single Photon Avalanche Diodes (SPADs) on a common silicon substrate, working in the limited Geiger mode and with a common readout. The fast counting ability, high timing resolution, immunity to magnetic field up to 15 T, low power consumption and relative small temperature dependence together with the small dimensions make SiPMs excellent candidates as commercially available solid state detectors, and a promising alternative to traditional photomultiplier tubes for single photon detection. Nevertheless, SiPMs do suffer from erroneous counting due to noise effects that can deteriorate their performances. These effects are, in general, heavily dependent on manufacturing quality. In this contribution, results are reported of the characterization of different models of SiPMs in terms of noise spectra and response to light, and a procedure for determining quality manufacturing parameters is described.

TUPC154

Commissioning of the Detection System for a Supersonic Gas-jets Based Transverse Beam Profile Monitor

ion, extraction, simulation, storage-ring

1392

M. Putignano, D. Borrows, A. Intermite
The University of Liverpool, Liverpool, United Kingdom
M. Putignano, M.R.F. Siggel-King, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Work supported by STFC, the EU under GA-ITN-215080, the Helmholtz Association and GSI under VH-NG-328.
We present the commissioning results of the Micro-Channel-Plate (MCP) based, ion extraction and detection system currently in use for an experimental test stand aimed at demonstrating the operation of a least-interceptive transverse beam profile monitor based on a planar supersonic gas-jet. This monitoring design features least-interceptive operation under excellent vacuum conditions and provides fast acquisition of a fully bi-dimensional transverse profile. It bears application for ultra-low energy particle beams at future storage rings, but also for e.g. linacs at high currents and light source injectors. For instance, the Ultra-low energy Storage Ring (USR), part of the Facility for Antiproton and Ion Research (FAIR) in Germany will store antiprotons at energies of 20-300 keV. In this contribution, we report numerical simulations and experimental results obtained by calibration of the detection system with a low energy electron beam to demonstrate a 1 mm imaging resolution only limited by recoiling ion drift.

TUPC158

Micron-scale Laser-wire at the ATF-II at KEK Commissioning and Results

laser, optics, photon, diagnostics

1401

L.J. Nevay, G.A. Blair, S.T. Boogert, L. Corner, L.C. Deacon, V. Karataev, R. Walczak
JAI, Oxford, United Kingdom
A.S. Aryshev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

We present the first results from the commissioning of the upgraded laser-wire experiment at the Accelerator Test Facility 2 (ATF2) at KEK. A new laser transport line and beam diagnostics were used to collide 150 mJ, 167 ps long laser pulses with 1.28 GeV, 30 ps long electron bunches to measure the vertical transverse size. Additionally, a new detector was installed with a reduced area for lower background. Initial scans showing a convoluted beam size of 19.2 ± 0.2 microns were used to tune the electron beam optics and reduce this down to 8.1 ± 0.1 microns. Laser pulse energy and charge dependency were investigated showing a linear relationship in both with a minimum laser energy of 20 mJ required for observable signal with this laser and setup.

TUPC159

Energy Measurements with Resonant Spin Depolarisation at Diamond

storage-ring, feedback, resonance, quadrupole

1404

I.P.S. Martin, M. Apollonio, R.T. Fielder, G. Rehm
Diamond, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom

A precise knowledge of the electron beam energy is critical for the accurate determination of many light source parameters, such as momentum compaction factor, natural chromaticity, energy stability and undulator spectra. In common with other facilities, a method of energy measurement based on resonant spin depolarisation has been developed at Diamond. In this paper we report on progress towards storage ring characterisation using this method, as well as describing the diagnostics developments that have enabled these measurements to be made.

TUPC162

Thin Foil-based Secondary Emission Monitor for Low Intensity, Low Energy Beam Profile Measurements

antiproton, proton, ion, target

1413

J. Harasimowicz, J.-L. Fernández-Hernando, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
L. Cosentino, P. Finocchiaro, A. Pappalardo
INFN/LNS, Catania, Italy
J. Harasimowicz
The University of Liverpool, Liverpool, United Kingdom

Funding: Work supported by STFC, the EU under GA-ITN-215080, the Helmholtz Association and GSI under VH-NG-328.
A secondary emission monitor (SEM) was developed for beam profile measurements at the Ultra-low energy Storage Ring (USR) that will be installed at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) in Darmstadt, Germany. The detector consists of an Aluminium foil on negative potential, a grounded mesh placed in front of the foil, a chevron type microchannel plate (MCP), a phosphor screen and a camera connected to a PC. Simulations of the optimized design together with experimental results with keV protons are presented in this contribution. In addition, the usability of the detector for low energy antiproton beam profile measurements is discussed.

TUPC165

DITANET - Investigations into Accelerator Beam Diagnostics

diagnostics, linac, instrumentation, extraction

1422

C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: Work supported by the EU under GA-PITN-215080.
DITANET is a Marie Curie initial training network in beam diagnostics. The network members, universities, research centres and industry partners, are developing diagnostics methods for a wide range of existing or future particle accelerators, both for electron and for ion beams. This is achieved through a cohesive approach that allows for the exploitation of synergies, whilst promoting knowledge exchange between partners. In addition to its broad research program, the network organizes schools and topical workshops for the beam instrumentation and particle accelerator communities. This contribution gives an overview of the Network's research outcomes to date and summarizes past and future training activities.

TUPC169

Single-shot Electro-optic Sampling of Coherent Transition Radiation at the A0 Photoinjector

laser, polarization, radiation, diagnostics

1431

T.J. Maxwell, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, USA

Funding: Work supported by Fermi Research Alliance, LLC under U.S. Dept. of Energy Contract No. DE-AC02-07CH11359, and Northern Illinois Univ. under US Dept. of Defense DURIP program Contract N00014-08-1-10⁶⁴.
Future collider applications and present high-gradient laser plasma wakefield accelerators operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation (*) or the bunch wakefields (**) with sub-picosecond time resolution. Potential applications in shot-to-shot, non-interceptive diagnostics continue to be pursued for live beam monitoring of collider and pump-probe experiments. Related to our developing work with electro-optic imaging, we present results on single-shot electro-optic sampling of the coherent transition radiation from bunches generated at the A0 photoinjector.
* J. van Tilborg et al., Phys. Rev. Lett. 96, 014801 (2006).
** M. J. Fitch et al., Phys. Rev. Lett. 87 034801 (2001).

TUPC170

Resonant TE Wave Measurements of Electron Cloud Densities at CesrTA

cavity, resonance, plasma, damping

1434

J.P. Sikora, M.G. Billing, M.A. Palmer, K.G. Sonnad
CLASSE, Ithaca, New York, USA
B.T. Carlson
CMU, Pittsburgh, Pennsylvania, USA
S. De Santis
LBNL, Berkeley, California, USA
K.C. Hammond
Harvard University, Cambridge, Massachusetts, USA

Funding: This work is supported by the US National Science Foundation PHY-0734867, and the US Department of Energy DE-FC02-08ER41538.
The Cornell Electron Storage Ring has been reconfigured as a test accelerator (CesrTA). Measurements of electron cloud densities have been made at CesrTA using the TE Wave transmission technique. However, interpretation of the data based on single pass transmission is problematic because of the reflections and standing waves produced by discontinuities in the beam pipe - from pumps, bellows, etc. that are normally present in an accelerator vacuum chamber. An alternative model is that of a resonant cavity, formed by the beampipe and its discontinuities. The theory for the measurement of plasma densities in cavities is well established. This paper will apply this theory to electron cloud measurements, present some simplified measurements on waveguide, and apply this model to the interpretation of some of the data taken at CesrTA.

TUPC171

2D Optical Streaking for Ultra-short Electron Beam Diagnostics

laser, simulation, diagnostics, linac

1437

L. Wang, Y.T. Ding, Z. Huang
SLAC, Menlo Park, California, USA

We propose a novel approach to measure the short electron bunch profile at micrometer level. Low energy electrons generated during beam-gas ionization are simultaneously modulated by the transverse electric field of a circularly-polarized laser, and then they are collected at a down-stream screen where the angular modulation are converted to a circular shape there. The longitudinal bunch profile is simply represented by the angular distribution of the electrons on the screen. We only need to know the laser wavelength for calibration and there is no phase synchronization problem. Meanwhile the required laser power is also relatively low in this setup. Some simulations examples and resolution of this method will be discussed.

TUPC172

Evaluation and Correction of the Non-linear Distortion of CEBAF Beam Position Monitors

simulation, pick-up, radiation

1440

M. Spata, T.L. Allison, K.E. Cole, J. Musson, J. Yan
JLAB, Newport News, Virginia, USA

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The beam position monitors at CEBAF have four antenna style pickups that are used to measure the location of the beam. There is a strong nonlinear response when the beam is far from the electrical center of the device. In order to conduct beam experiments at large orbit excitation we need to correct for this nonlinearity. The correction algorithm is presented and compared to measurements from our stretched wire BPM test stand.

TUPO002

High Flux Polarized Gamma Rays Production: First Measurements with a Four-mirror Cavity at the ATF

laser, cavity, positron, damping

1446

N. Delerue, J. Bonis, I. Chaikovska, R. Chiche, R. Cizeron, M. Cohen, P. Cornebise, R. Flaminio, D. Jehanno, F. Labaye, M. Lacroix, Y. Peinaud, L. Pinard, V. Soskov, A. Variola, Z.F. Zomer
LAL, Orsay, France
T. Akagi, S. Miyoshi
Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima, Japan
S. Araki, Y. Funahashi, Y. Honda, T. Omori, H. Shimizu, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
E. Cormier
CELIA, Talence, France
T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

Funding: ANR, IN2P3
The next generation of e+/e^- colliders will require the production of a very intense flux of gamma rays to allow polarized positrons to be produced in sufficient quantities. To demonstrate that this can be achieved a four-mirror cavity has recently been installed at the Accelerator Test Facility (ATF) at KEK to produce a high flux of polarized gamma rays by inverse Compton scattering. A four-mirror non-planar geometry is used to ensure the polarization of the gamma rays produced. The main mechanical features of the cavity are presented. A fibre amplifier is used to inject about 10W in the high finesse cavity with a gain of 1000. A digital feedback system is used to keep the cavity at the length required for the optimal power enhancement. First preliminary measurements show that on some beam crossings the interactions produce more than 25 photons with an average energy of about 24 MeV. Several upgrades currently in progress are described.

TUPO004

Generation of Attosecond Soft X-ray Pulses in a Longitudinal Space Charge Amplifier

undulator, space-charge, laser, radiation

1449

M. Dohlus, E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

A longitudinal space charge amplifier (LSCA), operating in soft x-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond x-ray pulses. It is shown that a compact and cheap addition to the soft x-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long x-ray pulses with the peak power at 100 MW level and a contrast above 98%.

TUPO005

Design Optimization for a Non-Planar Undulator for the JETI-Laser Wakefield Accelerator in Jena

undulator, laser, radiation, wakefield

1452

V. Afonso Rodriguez, T. Baumbach, A. Bernhard, G. Fuchert, A. Keilmann, P. Peiffer, C. Widmann
KIT, Karlsruhe, Germany
M. Kaluza, M. Nicolai
IOQ, Jena, Germany
R. Rossmanith
Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany

In a laser wakefield accelerator (LWFA), excited by a femtosecond laser pulse electrons are accelerated to several 100 MeV within a few centimeters. The energy spread of the electron beam is relatively large and varies from shot to shot. In order to obtain monochromatic photons in an undulator despite the energy spread, the following idea was proposed. Two bending magnets and a drift space in between produces dispersion so that particles with different energies have different transverse positions. The beam enters a non-planar undulator, e.g. cylindrical pole geometry, where the K-value also varies with transverse position. If the two variations in the transverse direction (particle energy and K-value) compensate each other the generated light is more monochromatic than with a conventional planar undulator. In this paper such a modified undulator design optimized for the JETI-LWFA in Jena is presented. An experiment to test this concept is in preparation.

TUPO006

Design of a Dispersive Beam Transport Line for the JETI Laser Wakefield Accelerators

undulator, radiation, dipole, quadrupole

1455

C. Widmann, V. Afonso Rodriguez, T. Baumbach, A. Bernhard, P. Peiffer
KIT, Karlsruhe, Germany
M. Kaluza, M. Nicolai
IOQ, Jena, Germany
R. Rossmanith
Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany

Laser wakeﬁeld accelerators (LWFA) emit electrons with energies of a few 100 MeV at very short bunch lengths while having a compact design. However, electron bunches from LWFA show a larger energy spread than those of conventional accelerators. This is a challenge when using these bunches e.g. to generate radiation in an undulator. A possible strategy to cope with that is to spectrally disperse the bunch and match the resulting spatial distribution with a spatially varying undulator ﬁeld amplitude. For realizing the dispersion a pair of dipole magnets is used. The electrons leaving this dipole chicane have to meet certain requirements imposed by the undulator: In the deﬂection plane the beam has to be collimated and its energy distribution must match the undulator ﬁeld. In the other transversal plane the beam has to be focussed on the center of the undulator keeping the value of the beta function small. To include this in the compact design of the setup, a combination of specially designed quadrupole and sextupole magnets is employed. In this contribution the design of the setup and the results of the particle tracking through this chicane are presented.

TUPO008

Electron Linac Optimization for Driving Bright Gamma-ray Sources based on Compton Back-scattering

photon, linac, laser, emittance

1461

L. Serafini, F. Broggi, C. De Martinis, D. Giove
Istituto Nazionale di Fisica Nucleare, Milano, Italy
D. Alesini, P. Antici, A. Bacci, M. Bellaveglia, R. Boni, E. Chiadroni, G. Di Pirro, A. Esposito, M. Ferrario, A. Gallo, G. Gatti, A. Ghigo, E. Pace, A.R. Rossi, B. Spataro, P. Tomassini, C. Vaccarezza
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
C. Maroli, V. Petrillo
Universita' degli Studi di Milano, Milano, Italy
M. Migliorati, A. Mostacci, L. Palumbo
Rome University La Sapienza, Roma, Italy

We study the optimal lay-out and RF frequency for a room temperature GeV-class Electron Linac aiming at producing electron beams that enhance gamma-ray sources based on Compton back-scattering. These emerging novel sources, generating tunable, mono-chromatic, bright photon beams in the range of 5-20 MeV for nuclear physics as well as nuclear engineering, rely on both, high quality electron beams and J-class high repetition-rate synchronized laser systems in order to achieve the maximum spectral density of the gamma-ray beam (# photons/sec/eV). The best option among the conventionally used RF linac-bands (S, C, X) and possible hybrid schemes will be analyzed and discussed, focusing the study in terms of best performances for the gamma-ray source, its reliability and compactness. We show that the best possible candidates for a Gamma-ray driver are quite similar to those of FEL Linacs.

TUPO013

Development of Pulse Width Measurement Techniques in a Picosecond Range of Ultra-short Gamma Ray Pulses

laser, photon, storage-ring, scattering

1473

Y. Taira, M. Hosaka, K. Soda, N. Yamamoto
Nagoya University, Nagoya, Japan
M. Adachi, M. Katoh, H. Zen
Sokendai - Okazaki, Okazaki, Aichi, Japan
T. Tanikawa
UVSOR, Okazaki, Japan

Funding: This work was supported by Grants-in-Aid for Scientific Research from Japan Society for the Promotion of Science (JSPS).
We are developing the ultra-short gamma ray pulse source with the energy of MeV region based on laser Compton scattering at the 750 MeV electron storage ring, UVSOR-II. Gamma rays with pulse width of sub-picosecond range can be generated by injecting femtosecond laser pulses into the electron beam from the vertical 90-degree direction* because the electron beam circulating in the storage ring is focused more tightly in the vertical direction than in the longitudinal direction. The energy, intensity, and pulse width of the gamma rays can be tuned by changing the collision angle between the electron beam and the laser. We are developing pulse width measurement techniques of ultra-short gamma ray pulses at present. As the first step of the pulse width measurement, we used a fast response photodetector, Geiger-mode APD, the time resolution of which is few hundreds picoseconds. Although we cannot measure the pulse width of the gamma rays with sub-picosecond range using this detector, we could measure the pulse width of the gamma rays as 430 ps or less by measuring the timing of Cherenkov radiations generated from the gamma rays.
* Y. Taira et al., Nucl. Instrum. Meth. A, in press, 2010.

TUPO014

High-flux Gamma-ray Generation by Laser Compton Scattering in the SAGA-LS Storage Ring

laser, photon, storage-ring, survey

1476

T. Kaneyasu, Y. Iwasaki, S. Koda, Y. Takabayashi
SAGA, Tosu, Japan

We constructed an experimental setup for high-flux gamma-ray generation by laser Compton scattering (LCS) in the SAGA-LS storage ring. The SAGA-LS is a synchrotron radiation (SR) facility consisting of a 255 MeV injector linac and a 1.4 GeV storage ring. We employed a CO2 laser having a wavelength of 10.6 micrometer to produce gamma-rays in the few MeV region in conjunction with the SR user time. The LCS gamma-ray up to the maximum energy of 3.5 MeV is generated via head-on collision between the laser photons and the 1.4 GeV stored beam. Since the energy acceptance of the storage ring is well above the maximum gamma-ray energy, the LCS experiment can be performed without reducing the beam lifetime. As a first step for high-flux gamma-ray generation, we use a small 10 W CO2 laser for beam test. The LCS event rate is designed to be 2·10⁸ ph/s with a beam current of 300 mA and a laser power of 10 W. A further increase of the LCS event rate in the order of 10¹0 ph/s is expected when a kW class laser is utilized. We report on the characteristics of the LCS gamma-rays observed in the low current beam test and an experimental result for evaluating the gamma-ray flux at a current of 300 mA.

TUPO017

Peculiarities of the Excitation of an Optical Resonator by an Electron Beam

undulator, radiation, damping, storage-ring

1479

E.G. Bessonov, M.V. Gorbunkov, A.L. Osipov
LPI, Moscow, Russia
A.A. Mikhailichenko
CLASSE, Ithaca, New York, USA

The peculiarities of the optical resonator excitation by electrons in a FEL based on the Self-Stimulated Undulator Radiation at main and collateral synchronicity conditions are discussed*.
* E.G.Bessonov et al., Self-Stimulated Undulator Radiation and its Possible Applications, http://arxiv.org/ftp/arxiv/papers/10⁰⁹/1009.3724.pdf

TUPO018

Self-stimulated Undulator Klystron

undulator, FEL, kicker, storage-ring

1482

E.G. Bessonov, A.L. Osipov
LPI, Moscow, Russia
A.A. Mikhailichenko
CLASSE, Ithaca, New York, USA

The Self Stimulated Undulator Klystron (SSUK) and its possible applications in the Particle Accelerator Physics, incoherent Self-Stimulated Undulator Radiation Sources (SSUR) and Free-Electron Lasers are discussed*.
* E.G.Bessonov et al., Self-Stimulated Undulator Radiation and its Possible Applications: http://arxiv.org/ftp/arxiv/papers/10⁰⁹/1009.3724.pdf

TUPO021

Dielectric Wakefield Accelerator to Drive the Future FEL Light Source

wakefield, FEL, linac, acceleration

1485

C.-J. Jing, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
J.G. Power, A. Zholents
ANL, Argonne, USA

X-ray free-electron lasers (FELs) are expensive instruments and a large part of the cost of the entire facility is driven by the accelerator. Using a high-energy gain dielectric wake-field accelerator (DWA) instead of the conventional accelerator may provide a significant cost saving and reduction of the facility size. In this article, we investigate using a collinear dielectric wakefield accelerator to provide a high repetition rate, high current, high energy beam to drive a future FEL x-ray light source. As an initial case study, a ~100 MV/m loaded gradient, 850 GHz quartz dielectric based 2-stage, wakefield accelerator is proposed to generate a main electron beam of 8 GeV, 50 pC/bunch, ~1.2 kA of peak current, 1MHz (10 beamlines) in just 100 meters with the fill factor and beam loading considered.

TUPO023

Narrow Spectral Bandwidth Optimization of Compton Scattering Sources

laser, scattering, simulation, emittance

1488

F. Albert, S.G. Anderson, S.M. Betts, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck, R.A. Marsh, M. J. Messerly, C. Siders, S.S.Q. Wu
LLNL, Livermore, California, USA

We will be presenting the theoretical and numerical design and optimization of Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering sources. A new precision source with up to 2.5 MeV photon energies, enabled by state of the art laser and x-band linac technologies, is currently being built at LLNL. Various aspects of the theoretical design, including dose and brightness optimization, will be presented. We will review the potential sources of spectral broadening, in particular due to the electron beam properties. While it is also known that nonlinear effects occur in such light sources when the laser normalized potential is close to unity, we show that these can appear at lower values of the potential. A three dimensional analytical model and numerical benchmarks have been developed to model the source characteristics based on given laser and electron beam distributions, including nonlinear spectra. Since MEGa-ray sources are being developed for precision applications such as nuclear resonance fluorescence, assessing spectral broadening mechanisms is essential.
This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

TUPO024

Precision X-band Linac Technologies for Nuclear Photonics Gamma-ray Sources

gun, laser, photon, scattering

1491

F.V. Hartemann, F. Albert, S.G. Anderson, C.P.J. Barty, A.J. Bayramian, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, T.L. Houck, R.A. Marsh, M. J. Messerly, S.S.Q. Wu
LLNL, Livermore, California, USA
C. Adolphsen, A.E. Candel, T.S. Chu, M.V. Fazio, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou
SLAC, Menlo Park, California, USA
D. Cutoiu
Horia Hulubei National Institute for Physics and Nuclear Engineering, Bucharest, Romania
D. Ighigeanu, M. Toma
INFLPR, Bucharest - Magurele, Romania
V.A. Semenov
UCB, Berkeley, California, USA

Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within this context, high-gradient X-band technology will be shown to offer optimal performance in a compact package, when used in conjunction with the appropriate pulse format, and photocathode illumination and interaction laser technologies.

TUPO029

Status of the BERLinPro Optics Design

emittance, linac, vacuum, optics

1500

A.N. Matveenko, M. Abo-Bakr, A.V. Bondarenko, A. Jankowiak, J. Knobloch, B.C. Kuske, Y. Petenev
HZB, Berlin, Germany

Following funding approval late 2010, Helmholtz-Zentrum Berlin officially started Jan. 2011 the design and construction of the Berlin Energy Recovery Linac Project BERLinPro. The initial goal of this compact ERL is to develop the ERL accelerator physics and technology required to accelerate a high-current (100 mA) low emittance beam (1 mm•mrad normalized), as required for future ERL-based synchrotron light sources. Given the flexibility ERLs provides, a short bunch operation mode will also be investigated. Current optics was designed to allow of low emittance and short bunch operation modes. Optics is flexible to suppress BBU and minimize CSR effects. Estimation of impact of ion accumulation, wake fields, halo and chromatic aberrations is given. Requirements for beam diagnostic system, alignment accuracy and power supply stability are investigated.

TUPO031

The Shielding Design of BERLinPro

neutron, shielding, radiation, linac

1503

K. Ott, M. Helmecke
HZB, Berlin, Germany

Funding: Funded by the Bundesministerium für Bildung und Forschung and by the Land Berlin.
The Helmholtz-Zentrum Berlin started in January 2011 the design and construction of the Berlin Energy Recovery Linac Project BERLinPro as a demonstrator of ERL science and technology. BERLinPro consists of a SRF photo injector, a merger, superconducting booster and linac modules, the ring and a beamdump. The energy is 50 MeV, the maximum current is 100 mA (cw), acceleration to higher energies is an option for the future. The low energy parts of the machine are operated at about 10 MeV. Due to the potential radiation hazard posed by the tremendous beampower the facility will be placed subterraneously. The shielding concept is presented here. We used the Monte Carlo code FLUKA to calculate the details of the shielding, activations, energy doses for radiation damage and energy spectra for realistic scenarios. Due to computing time reasons we used FLUKA calculations in the 50 MeV to 1 GeV range to derive analytical formulas for the vertical shielding. Extrapolation of existing formulas valid in the GeV range (or below 100 MeV) are not applicable because of the rapidly increasing cross section of photo pion production between 100 and 200 MeV.

TUPO034

Longitudinal Stability of ERL with Two Accelerating RF Structures

linac, cavity, RF-structure, simulation

1509

Ya.V. Getmanov, O.A. Shevchenko
BINP SB RAS, Novosibirsk, Russia
N. Vinokurov
NSU, Novosibirsk, Russia

Modern ERL projects use superconductive accelerating RF structures. Their RF quality is typically very high. Therefore, the RF voltage induced by electron beam is also high. In ERL the RF voltage induced by the accelerating beam is almost canceled by the RF voltage induced by the decelerating beam. But, a small variation of the RF voltage may cause the deviations of the accelerating phases. These deviations then may cause further voltage variation. Thus the system may be unstable. The stability conditions for ERL with one accelerating structure are well known [*, **]. The ERL with split RF structure was discussed recently [***, ****]. The stability conditions for such ERLs are discussed in this paper.
* L. Merminga et al.,Annu. Rev.Nucl. Part. Sci. 53 (2003) 387.
** N.A. Vinokurov et al.,Proc. SPIE 2988 (1997) 221.
*** D. Douglas, ICFA BD-Nl 26 (2001) 40.
****N.A. Vinokurov et al.,Proc. IPAC’10.

TUPS002

Photodesorption Measurements at ESRF D31

vacuum, radiation, synchrotron, synchrotron-radiation

1518

H.P. Marques, G. Debut, M. Hahn
ESRF, Grenoble, France

Since 1998 exists at ESRF a dedicated beamline for photodesorption measurement from vacuum chambers - D31. The original goal of this installation was to study the wall pumping effect. When exposed to synchrotron radiation surfaces exhibit strong outgassing of the adsorbed gas layer despite UHV conditions. Long term outgassing leads to the depletion of the adsorbed layer and produces a very clean surface which turns the walls of the vacuum chamber into an active pumping surface. The desorption mechanisms can be described by the long standing models of Knotek-Feibelman (KF) and Menzel-Gomer-Redhead – (MGR) which are themselves encompassed under the name of Desorption Induced by Electronic Transitions (DIET). In these models the surface itself plays a fundamental role in the desorption mechanism. At D31 have been tested chambers of stainless steel, aluminum and copper, with or without coatings (e.g. NEG, copper), designed by ESRF and other institutes like ALBA, CERN, ELETTRA and Soleil. Here we review some of the results obtained and outline the future plans of D31.

TUPS004

Enhanced High-voltage Holding under Vacuum by Field Induced Adsorption of Gas on Metal Surfaces

high-voltage, vacuum, cathode, plasma

1524

A. Simonin, L. Christin, L. Doceul, F. Faisse, F. Villecroze, H. de Esch
CEA, St Paul Lez Durance, France

*The energy of future neutral beam injector heating systems of fusion power plants ranges from 1 to 2 MeV. The beam line and the reactor chamber are under vacuum, while all the electrical components (power supplies) are connected to the injector via a long pressured (SF6) high-voltage (1-2 MV) transmission line. The bushing is a key component that ensures the barrier between the transmission line and the injector under vacuum; the design of this component is very challenging as it faces several stringent constraints due to the nuclear environment, in which high-voltage holding, mechanical stresses, and radiations are combined. Moreover, it is a high-voltage feed-through that allows supply of the accelerator electrodes with electrical power, active water cooling, and gas. In this paper, a new high-voltage bushing concept based on experimental findings previously obtained in the laboratory is presented. The main advantages of the concept is a reduction of the electron field emission under vacuum, which is an issue for conventional bushings, a reduction in size, and mechanical simplification of the device resulting in cost reduction and greater reliability."

TUPS008

The Gas Attenuator Vacuum System of FERMI@Elettra

vacuum, photon, radiation, FEL

1530

L. Rumiz, D. Cocco, C. Fava, S. Gerusina, R. Gobessi, E. Mazzucco, F. Zudini
ELETTRA, Basovizza, Italy
M. Zangrando
IOM-CNR, Trieste, Italy

The FERMI@Elettra Free Electron Laser aims to produce a coherent light in the EUV-soft X-ray range employing High Gain Harmonic Generation (HGHG) schemes. The ultrafast, high intensity pulses are delivered to the experimental stations by means of a section called PADReS (Photon Analysis Delivery and Reduction System). Since several experiments need to reduce the FEL radiation intensity without changing the machine parameters, PADReS provides an integrated system to measure and reduce it up to 4 orders of magnitude. It is composed by a windowless gas-filled cell, a gas injection system, a differential pumping system, and the intensity monitors. The gas cell can be filled up to 0.15 mbar of nitrogen and the differential pumping system can keep up over 6 orders of magnitude. The pressure is finely regulated in the ·10^-5 mbar range in the intensity monitor vacuum chamber, almost independently from the gas cell pressure level. The general layout and the performance of the differential pumping system prototype are presented.

TUPS009

SEY of Al Samples from the Dipole Chamber of PETRA III at DESY

emittance, simulation, synchrotron, synchrotron-radiation

1533

D. R. Grosso, R. Cimino, M. Commisso
INFN/LNF, Frascati (Roma), Italy
R. Flammini
CNR-IMIP, Monterotondo Stazione RM, Italy
R. Larciprete
ISM-CNR, Rome, Italy
R. Wanzenberg
DESY, Hamburg, Germany

At the synchrotron radiation facility PETRA III, tune spectra have been measured with some characteristics which are typically observed at other storage rings in connection with electron cloud effects. For some bunch filling patterns, an increase of the vertical emittance has been observed. To estimate such effects with the available e-cloud simulation codes, the detailed knowledge of the SEY (Secondary Electron Yield) of the Al chamber, is required. To the purpose, representative PETRA III Al samples, were studied in detail at the INFN-LNF Surface Science Laboratory. XPS (X-ray photoelectron spectroscopy) and SEY measurements were performed as a function of electron and argon ion conditioning. The SEY of the as received samples shows a maximum value of δmax ≅ 2.8. Electron conditioning at 500 eV kinetic energy, reduces the SEY to values between δmax ≅ 1.8 to 1.4 (depending on the actual sample analyzed). The XPS characterization of the sample surface, after several cycles of argon ion sputtering, shows clearly that the SEY variation is closely related to the oxidation state of the Al sample, reaching a δmax value as low as 1.3 for our cleanest surface.

TUPS012

The Present Status of Vacuum System of XFEL in SPring-8

vacuum, shielding, undulator, laser

1542

T. Bizen
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Hasegawa
RIKEN/SPring-8, Hyogo, Japan

The vacuum component assembly and installation were completed by February in 2011. The total length of the vacuum system is about 630 m. A 455 sputter ion pumps and a 10⁸ NEG cartridge pumps generate vacuum. The average pressures are on the order of ·10^-7 Pa or less. The flange developed for C-band waveguide shows high reliability of vacuum seal.

TUPS018

Observations of Electron Cloud Effects with the LHC Vacuum System

vacuum, solenoid, simulation, ion

1560

V. Baglin, G. Bregliozzi, P. Chiggiato, P. Cruikshank, B. Henrist, J.M. Jimenez, G. Lanza
CERN, Geneva, Switzerland

In autumn 2010, during the LHC beam commissioning, electron-cloud effects producing pressure rise in common and single vacuum beam pipes, were observed. To understand the potential limitations for future operation, dedicated machine studies were performed with beams of 50 and 75 ns bunch spacing at energy of 450 GeV. In order to push further the LHC performances, a scrubbing run was held in spring 2011. This paper summarizes the vacuum observations made during these periods. The effects of bunch intensity and different filling schemes on the vacuum levels are discussed. Simulations taking into account the effective pumping speed at the location of the vacuum gauge are introduced. As a consequence, the different vacuum levels observed along the LHC ring could be explained. Finally, the results obtained during the scrubbing run are shown together with an estimation of pressure profiles during the 2011 run.

TUPS023

Secondary Electron Yield on Cryogenic Surfaces as a Function of Physisorbed Gases

cryogenics, vacuum, gun, insertion

1575

A. Kuzucan, H. Neupert, M. Taborelli
CERN, Geneva, Switzerland
H. Stoeri
IAP TUW, Wien, Austria

Electron cloud is a serious limitation for the operation of particle accelerators with intense positively charged beams. It occurs if the secondary electron yield (SEY) of the beam-pipe surface is sufficiently high to induce an electron multiplication. At low surface temperatures, the SEY is strongly influenced by the nature of the physisorbed gases and by the corresponding surface coverage. These conditions occur in many accelerators operating with superconducting magnets and cold vacuum sections such as the LHC and RHIC. In this work, we investigated the variation of the SEY of copper, aluminium and electro-polished copper as a function of physisorbed N2, CO, CO2, CH4, Kr, C2H6 at cryogenic temperatures. The conditioning by electron bombardment of the surface after the physisorption of H2O on electro polished copper will also be presented. The results of the various gases are compared in order to find a rationale for the behaviour of the secondary electrons for the various adsorbates.

TUPS024

Development of Beryllium Vacuum Chamber Technology for the LHC

vacuum, collider, controls, background

1578

R. Veness
CERN, Geneva, Switzerland
C. Dorn, G. Simmons
Materion Electrofusion, Fremont, California, USA

Beryllium is the material of choice for the beam vacuum chambers around collision points in particle colliders due to a combination of transparency to particles, high specific stiffness and compatibility with ultra-high vacuum. New requirements for these chambers in the LHC experiments have driven the development of new methods for the manufacture of beryllium chambers. This paper reviews the requirements for experimental vacuum chambers. It describes the new beryllium technology adopted for the LHC and experience gained in the manufacture and installation.

TUPS027

Characterization of Carbon Coatings with Low Secondary Electron Yield

vacuum, cryogenics, ion, gun

1587

C. Yin Vallgren, S. Calatroni, P. Costa Pinto, A. Kuzucan, H. Neupert, M. Taborelli
CERN, Geneva, Switzerland

Amorphous carbon (a-C) coatings can reliably be produced with a maximum secondary electron yield (SEY) close to 1 at room temperature. Measurements at low temperature (LHe) are in progress. Analysis by X-ray Photoemission Spectroscopy (XPS) shows a correlation between the lineshape of C1s spectrum in XPS and maximum SEY of the investigated samples. The initial level of oxygen on the surface of the various samples does not seem to be related to the initial maximum SEY value. However, the increase of the SEY with air exposure time on each individual sample is related to the amount of oxygen containing adsorbates. Storage in different environments has been investigated (static vacuum, aluminum foil, dry nitrogen and desiccators) and shows significant differences in the “aging” behavior. Aging is very moderate when storing samples wrapped in aluminum foil in air. Samples which have undergone aging due to inappropriate storage can be recovered nearly to the initial value of the SEY by typical surface treatments as ion bombardment, annealing under vacuum and conditioning by electron beam. However, an enhanced sensitivity to air exposures is observed for most of these curing methods.

TUPS028

Performance of Carbon Coating for Mitigation of Electron Cloud in the SPS

dipole, vacuum, insertion, extraction

1590

C. Yin Vallgren, P. Chiggiato, P. Costa Pinto, H. Neupert, G. Rumolo, E.N. Shaposhnikova, M. Taborelli
CERN, Geneva, Switzerland

Amorphous carbon (a-C) coatings have been tested in electron cloud monitors (ECM) in the Super Proton Synchrotron (SPS) and have shown for LHC type beams a reduction of the EC current by a factor 10⁴ compared to stainless steel (SS). This performance has been maintained for more than 2 years under SPS operation conditions. Secondary electron yield (SEY) laboratory data confirm that after 1 year of SPS operation, the coating maintains a SEY below 1. The compatibility of coexisting SS and a-C surfaces has been studied in an ECM having coated and uncoated areas. The results show no degradation of the properties of the a-C areas. The performance of diamond like carbon (DLC) coating has also been studied. DLC shows a less effective reduction of the EC current than a-C, but conditioning is faster than for SS. Three a-C coated dipoles were inserted in the SPS. However, even with no EC detected, the dynamic pressure rise is similar to the one observed in the SS reference dipoles. Measurement in a new ECM equipped with clearing electrodes to verify the relation between pressure signals and intensity of the EC, as well as an improvement of the diagnostics in the dipoles are in progress.

TUPS030

Manufacturing and Vacuum Testing of Aluminum Bending Chambers for TPS

vacuum, ion, photon, synchrotron

1596

Y.C. Yang, C.K. Chan, C.-C. Chang, C.L. Chen, J.-R. Chen, G.-Y. Hsiung, S-N. Hsu, T.Y. Lee
NSRRC, Hsinchu, Taiwan

The Taiwan Photon Source (TPS) is an aluminum alloy vacuum system with 518.4 m circumference divided into 24 sections. A6061T6 aluminum alloy material is used for TPS bending chambers. Each aluminum bending chamber is component of 2 half plates, about 3.5～4.2 m in length and～0.6 m in width, were oil-free CNC machined, ozone cleaned, and TIG welding in clean room. The deformation < 0.1 mm and leakage rate < 2x10-9mbar. L/s for each welded bending chamber has inspected and achieved. A bending chamber is inspecting the thermal outgassing rate test and ultimate pressure. The manufacturing and vacuum test will be described in this paper.

TUPS056

Synchronizing GEANT and 3D CAD - A Collaborative Engineering Study at ILD

simulation, free-electron-laser, laser

1659

L. Hagge, S. Eucker, B. List, S. Sühl, N. Welle
DESY, Hamburg, Germany

The design of a detector for a high-energy physics experiment is a complex task, driven by two different communities: The scientists aim to optimize the detector performance, while engineers are tasked to provide a design that can actually be built. Both groups have their own specific tools (e.g. GEANT versus 3D CAD systems) that are employed to model the detector and improve its design. The ensuing models need to be compared and synchronized at regular intervals, so that optimizations made to the physics simulation model are propagated to the engineering world, and engineering solutions are reflected properly in the physics simulation. Based on experience from the European XFEL project, DESY is providing tools and processes for establishing this synchronization at a very early stage in the design of the International Large Detector (ILD) for the International Linear Collider (ILC). They have been used to analyze compliance and differences of the ILD engineering design and physics simulation models. The poster introduces tools and process and presents first results and lessons learned.

TUPS073

Top-Up Safety Simulations for the TPS Storage Ring

storage-ring, quadrupole, sextupole, photon

1707

H.-J. Tsai, C.C. Chiang, P.J. Chou, C.-C. Kuo
NSRRC, Hsinchu, Taiwan

TPS is a 3 GeV third generation light source and operates in the top-up injection scheme. During the top-up injection, the beamline photon shutters are always open. To ensure the radiation safety of beamline experiments, we studied the possible particle leakage to ID and neighboring bending beamlines. The effects of errors on magnets and beam chamber alignments are investigated.

TUPS077

Shaping of Ion Pulses from an Electron Beam Ion Source for Particle Injection into Accelerators

ion, ion-source, proton, injection

1716

F. Ullmann, A. Schwan
DREEBIT GmbH, Dresden, Germany
U. Hagen, O. Heid, H. von Jagwitz
Siemens AG, Healthcare Technology and Concepts, Erlangen, Germany
G. Zschornack
Technische Universität Dresden, Institut für Angewandte Physik, Dresden, Germany

Electron Beam Ion Sources (EBISs) provide highly charged ions for many applications, amongst others for particle injection into accelerators. Although EBISs are limited in ion output they feature a lot of advantages which qualify them for accelerator injection. The ion pulses extracted from the ion sources can be directly injected into an accelerator sequence which however requires ion pulses with distinct shape and length. We present the production of ion pulses matching the requirements of particle injection. The ions are produced by trapping in a high density electron beam for a certain time with electrostatic potentials providing for their axial trapping. The ions are extracted by lowering the trapping potential, i.e. opening the trap. Due to the ion energy distribution within the trapping region ion extraction can be controlled by controlling the trapping potential. A specific time dependent control mode of the trapping potential thus allows to produce ion pulses with designated shape and length. Source parameters such as working gas pressure, electron beam current and energy are influencing the energy distribution of the ions which in turn is influencing pulse shaping.

TUPS078

Electron Beam Ion Sources – A New Access for Particle Acceleration

ion, ion-source, emittance, injection

1719

F. Ullmann, F. Grossmann, V.P. Ovsyannikov, A. Schwan
DREEBIT GmbH, Dresden, Germany
G. Zschornack
Technische Universität Dresden, Institut für Angewandte Physik, Dresden, Germany

Electron Beam Ion Sources (EBISs) produce highly charged ions in a high density electron beam. Due to their operational principle EBISs have a lot of advantages although limited in ion output. Since the radial source region is given by a narrow electron beam the extracted ion beam features a very low transversal emittance. Moreover, the ions are ionized by a monoenergetic electron beam resulting in a small variation of the ion energy distribution, and thus in a very low longitudinal emittance. Together with a low basis pressure of less than 10^-9 mbar this result in a high quality ion beam. The ions can be extracted as continuous beam as well as ion pulses with distinct pulse shapes. Providing almost any element with any charge state of up to completely ionized ions gives a large number of different projectiles and kinetic energies. The use of EBISs whether based on permanent magnets or on cryogen-free superconducting magnets has been proven in a variety of fields and applications. In addition, their compact design makes them transportable, low in operational costs, and guarantee easy handling.

TUPS085

Mass Production Report of C-band Choke Mode Accelerating Structure and RF Pulse Compressor

resonance, coupling, cavity, acceleration

1737

S. Miura, T. Hashirano, F. Inoue, K. Okihira
MHI, Hiroshima, Japan
T. Inagaki
RIKEN/SPring-8, Hyogo, Japan
H. Maesaka, T. Shintake
RIKEN Spring-8 Harima, Hyogo, Japan

RIKEN and JASRI already completed the construction of XFEL/SPring8. Recently the facility was named “SACLA” (SPring-8 Angstrom Compact Free Electron LAser). The commissioning team succeeded in acceleration of 8 GeV electron beam and observation of the undulator light of 0.8 angstrom wavelength in March 2011. Now the accelerator is stably operated for the XFEL commissioning. In this project, a C-band (5712 MHz) choke mode accelerating structures and C-band RF pulse compressors are employed to obtain a high acceleration gradient of more than 35 MeV/m. We completed the fabrication of 128 accelerating structures, 64 RF pulse compressors, and 64 units of waveguide components and conducted RF measurements on them until May 2010. We report the result of the mass-production of these 64 C-Band units.

TUPS097

In-situ Experiments of Vacuum Discharge using Scanning Electron Microscopes

vacuum, ion, site, high-voltage

1765

T. Muranaka, V.G. Ziemann
Uppsala University, Uppsala, Sweden
T. Blom, K. Leifer
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden

Funding: This work is supported by the 7th European Framework Program EuCARD under grant number 227579
Fundamental understandings of vacuum discharge mechanisms and involving surface damage is an indispensable for CLIC feasibility study. We have been conducting dc experiments inside a Scanning Electron Microscope (SEM) at Uppsala university in order to investigate localised breakdown phenomena. By using a SEM, we achieve the resolution of the electron probe in the few-nm range, which is of great advantage as the surface roughness of the polished accelerating structures is in the same scale. The high accelerating field of 1 GV/m is realised by biasing an electrode with 1 kV set above the sample with a gap of sub μm. Furthermore, a second SEM equipped with a Focused Ion Beam (FIB) is used to modify the topography of sample surfaces thus the geometrical dependence of field emissions and vacuum discharges could be studied. The FIB can be used for the surface damage analysis as well. We have demonstrated subsurface damage observations by using FIB to sputter a rectangular recess into the sample in the breakdown region. Those powerful surface analysis techniques can be productively applied to the study of fatigue in prototype accelerating structures.

TUPS098

Machining and Characterizing X-band RF-structures for CLIC

controls, cavity, damping, collider

1768

S. Atieh, M. Aicheler, G. Arnau-Izquierdo, A. Cherif, L. Deparis, D. Glaude, L. Remandet, G. Riddone, M. Scheubel
CERN, Geneva, Switzerland
D. Gudkov, A. Samoshkin, A. Solodko
JINR, Dubna, Moscow Region, Russia

The Compact Linear Collider (CLIC) is currently under study at CERN as a potential multi-TeV e+e collider. The manufacturing and assembling tolerances for making the required RF components are essential for CLIC to perform efficiently. Machining techniques are relevant to the construction of ultra-high-precision parts for the Accelerating Structures (AS). Optical-quality turning and ultra-precision milling using diamond tools are the main manufacturing techniques identified to produce ultra-high shape accuracy parts. A shape error of less than 5 micrometres and roughness of Ra 0.025 are achieved. Scanning Electron Microscopy (SEM) observation as well as sub-micron precision Coordinate Measuring Machines (CMM), roughness measurements and their crucial environment were implemented at CERN for quality assurance and further development. This paper focuses on the enhancements of precision machining and characterizing the fabrication of AS parts.

TUPS099

A Study of the Surface Quality of High Purity Copper after Heat Treatment

vacuum, damping, linear-collider, collider

1771

M. Aicheler, G. Arnau-Izquierdo, S. Atieh, S. Calatroni, S. Lebet, G. Riddone, A. Samoshkin
CERN, Geneva, Switzerland

The manufacturing flow of accelerating structures for the compact linear collider, based on diamond-machined high purity copper components, include several thermal cycles (diffusion bonding, brazing of cooling circuits, baking in vacuum, etc.). The high temperature cycles may be carried out following different schedules and environments (vacuum, reducing hydrogen atmosphere, argon, etc.) and develop peculiar surface topographies which have been the object of extended observations. This study presents and discusses the results of scanning electron microscopy (SEM) and optical microscopy investigations.

TUPS105

Beam Brightness Booster with Self-Stabilization of Electron-Proton Instability

ion, brightness, space-charge, proton

1789

V.G. Dudnikov, C.M. Ankenbrandt
Muons, Inc, Batavia, USA

The brightness and intensity of a circulating proton beam now can be increased up to the space charge tune shift limit by means of charge exchange injection or by electron cooling but cannot be increased above this limit. Significantly higher brightness can be produced by means of charge exchange injection with space charge compensation*. The brightness of the space charge compensated beam is limited at low level by an electron-proton (e-p) instability. Fortunately, the e-p instability can be self-stabilized at a high beam density. The “cesiation effect” significantly increases negative ion emission from gas discharges, and surface-plasma sources for intense high brightness negative ion beam production have been developed. These developments make it possible to produce stable “superintense” circulating beams with intensity and brightness far above the space charge limit. A beam brightness booster (BBB) for significant increases of accumulated beam brightness is discussed. Superintense beam production can be simplified by developing a nonlinear nearly-integrable focusing system with broad betatron tune spread and a broadband feedback system for e-p instability suppression.
* M. Reiser, “Theory and Design of Charged Particle Beam”, second edition, p. 565-570, Wiley-VCH, (2006).

TUPS106

Absorber Materials at Room and Cryogenic Temperatures*

HOM, cavity, cryogenics, damping

1792

F. Marhauser, T.S. Elliott, A.T. Wu
JLAB, Newport News, Virginia, USA
E.P. Chojnacki
CLASSE, Ithaca, New York, USA
E. Savrun
Sienna Technologies Inc., Woodinville, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We recently reported on investigations of RF absorber materials at cryogenic temperatures conducted at Jefferson Laboratory (JLab). The work was initiated to find a replacement material for the 2 Kelvin low power waveguide Higher Order Mode (HOM) absorbers employed within the original cavity cryomodules of the Continuous Electron Beam Accelerator Facility (CEBAF). This effort eventually led to suitable candidates as reported in this paper. Furthermore, though constrained by small funds for labor and resources, we have analyzed a variety of lossy ceramic materials, several of which could be usable as HOM absorbers for both normal conducting and superconducting RF structures, e.g. as loads in cavity waveguides and beam tubes either at room or cryogenic temperatures and, depending on cooling measures, low to high operational power levels.

TUPZ003

Simulation of Electron-cloud Build-Up for the Cold Arcs of the LHC and Comparison with Measured Data

simulation, dipole, vacuum, injection

1801

G.H.I. Maury Cuna
CINVESTAV, Mérida, Mexico
G. Arduini, G. Rumolo, L.J. Tavian, F. Zimmermann
CERN, Geneva, Switzerland

The electron cloud generated by synchrotron radiation or residual gas ionization is a concern for LHC operation and performance. We report the results of simulations studies which examine the electron cloud build-up, at injection energy, 3.5 TeV for various operation parameters In particular we determine the value of the secondary emission yield corresponding to the multipacting threshold, and investigate the electron density, and heat as a function of bunch intensity for dipoles and field-free regions. We also include a comparison between simulations results and measured heat-load data from the LHC scrubbing runs in 2011

TUPZ015

Electron Cloud Parameterization Studies in the LHC

vacuum, simulation, emittance, beam-losses

1834

C.O. Domínguez, G. Arduini, V. Baglin, G. Bregliozzi, J.M. Jimenez, E. Métral, G. Rumolo, D. Schulte, F. Zimmermann
CERN, Geneva, Switzerland

During LHC beam commissioning with 150, 75 and 50-ns bunch spacing, important electron-cloud effects, like pressure rise, cryogenic heat load, beam instabilities or emittance growth, were observed. The main strategy to combat the LHC electron cloud relies on the surface conditioning arising from the chamber-surface bombardment with cloud electrons. In a standard model, the conditioning state of the beam-pipe surface is characterized by three parameters: 1. the secondary emission yield; 2. the incident electron energy at which the yield is maximum; and 3. the probability of elastic reflection of low-energy primary electrons hitting the chamber wall. Since at the LHC no in-situ secondary-yield measurements are available, we compare the relative local pressure-rise measurements taken for different beam configurations against simulations in which surface parameters are scanned. This benchmark of measurements and these simulations is used to infer the secondary-emission properties of the beam-pipe at different locations around the ring and at various stages of the surface conditioning. In this paper we present the methodology and first results from applying the technique to the LHC.

TUPZ033

Measurements of Transverse Beam Diffusion Rates in the Fermilab Tevatron Collider

antiproton, background, collider, emittance

1882

G. Stancari, G. Annala, T.R. Johnson, D.A. Still, A. Valishev
Fermilab, Batavia, USA

Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. This work was partially supported by the US LHC Accelerator Research Program (LARP).
The transverse beam diffusion rate vs. particle oscillation amplitude was measured in the Tevatron using collimator scans. All collimator jaws except one were retracted. As the jaw of interest was moved in small steps, the local shower rates were recorded as a function of time. By using a diffusion model, the time evolution of losses could be related to the diffusion rate at the collimator position. Preliminary results of these measurements are presented.

Poster TUPZ033 [1.036 MB]

WEXA01

Challenges of 4th Generation Light Sources

FEL, emittance, undulator, photon

3798

C. Pellegrini
SLAC, Menlo Park, California, USA
C. Pellegrini
UCLA, Los Angeles, California, USA

In the last few years Free Electron Lasers (FELs) have emerged as exceptionally exciting tools for new science. The results from FLASH (Hamburg) on biological imaging, LCLS (Stanford) which generated the first hard X-ray lasing and the projects proposed or in costruction around the world are rapidly moving the scientific community to the so called “fast science” which demands ultrashort pulses, fs synchronization, high brightness, high coherence X-rays. The basic SASE FEL process used so far converts energy jitter into jitter of the centralwavelength. Processes based on seeding and HGHG seem to offer a number of advantages in terms of bandwidth, coherence, stability and undulator length. This talk will present an overview of the 4th generation light sources, discussing the main challenges afforded in the construction of the operating facilities and considering the trends for the development of future facilities.

Slides WEXA01 [10.640 MB]

WEOAA02

Performance of 2 MeV, 2 kA, 200 ns Linear Induction Accelerator with Ultra Low Beam Emittance for X-Ray Flash Radiography

target, focusing, cathode, induction

1906

P.V. Logachev, A. Akimov, P.A. Bak, M.A. Batazova, A.M. Batrakov, Y.M. Boimelshtain, D. Bolkhovityanov, A.A. Eliseev, F.A. Emanov, G.A. Fatkin, A.A. Korepanov, Ya.V. Kulenko, G.I. Kuznetsov, I.V. Nikolaev, A.V. Ottmar, A.A. Pachkov, A. Panov, O.A. Pavlov, D.A. Starostenko
BINP SB RAS, Novosibirsk, Russia

Funding: The minestry of education and science of Russian Federation R&D contracts:P2493 and 14.740.11.0160
LIA-2 linear induction accelerator is designed in Budker INP as an injector for full scale 20 MeV linear induction accelerator which can be used for X-ray flash radiography with high space resolution. This machine utilizes ultra high vacuum, precise beam optics design based on low temperature dispenser cathode of 190 mm in diameter. The results of LIA-2 commissioning are presented. The designed value of beam emittance (120 π mm•mrad, not normalized) is achieved at 2 MeV and 2 kA of electron beam energy and current.

Slides WEOAA02 [7.094 MB]

WEOAA03

Approach to a Start-to-end Simulation of 2-loop Compact Energy Recovery Linac

simulation, emittance, linac, optics

1909

M. Shimada, K. Harada, Y. Kobayashi, T. Miyajima, N. Nakamura, S. Sakanaka
KEK, Ibaraki, Japan
R. Hajima
JAEA, Ibaraki-ken, Japan

Transport of an extreme low emittance electron beam is critical issue in an energy recovery linac. In particlar, the space charge effect on an electron bunch in the injector with lower than 5 - 10 MeV induces a large emittance growth. To suppress the emittance growth by such as an optimization of the solenoid magnets, a nonlinear effect should be clarified by a three dimensional tracking simulation. The cons is that it consumes a enormous simulation time. The approach is not suitable for a double loop circulation because the simulation time depends on the transport length. Therefore the beam dynamics and optics are calculated by a start-to-end (S2E) simulation, in which the simulation code is switched after the full acceleration. We used 'general particle tracking (GPT)' for injector electron beam and 'elegant' for a circulator electron beam.

Slides WEOAA03 [3.951 MB]

WEOBA01

ARIEL: TRIUMF’s Advanced Rare IsotopE Laboratory

target, TRIUMF, ISAC, proton

1917

L. Merminga, F. Ames, R.A. Baartman, C.D. Beard, P.G. Bricault, I.V. Bylinskii, Y.-C. Chao, R.J. Dawson, D. Kaltchev, S.R. Koscielniak, R.E. Laxdal, F. Mammarella, M. Marchetto, G. Minor, A.K. Mitra, Y.-N. Rao, M. Trinczek, A. Trudel, V.A. Verzilov, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

TRIUMF has recently embarked on the construction of ARIEL, the Advanced Rare Isotope Laboratory, with the goal to significantly expand the Rare Isotope Beam (RIB) program for Nuclear Physics and Astrophysics, Nuclear Medicine and Materials Science. ARIEL will use proton-induced spallation and electron-driven photo-fission of ISOL targets for the production of short-lived rare isotopes that are delivered to experiments at the existing ISAC facility. Combined with ISAC, ARIEL will support delivery of three simultaneous RIBs, up to two accelerated, new beam species and increased beam development capabilities. The ARIEL complex comprises a new SRF 50 MeV 10 mA CW electron linac photo-fission driver and beamline to the targets; one new proton beamline from the 500 MeV cyclotron to the targets; two new high power target stations; mass separators and ion transport to the ISAC-I and ISAC-II accelerator complexes; a new building to house the target stations, remote handling, chemistry labs, front-end and a tunnel for the proton and electron beamlines. This report will include overview of ARIEL, its technical challenges and solutions identified, and status of design activities.

Slides WEOBA01 [3.676 MB]

WEODA02

Collimation Studies with Hollow Electron Beams

collimation, antiproton, gun, proton

1939

G. Stancari, G. Annala, T.R. Johnson, G.W. Saewert, V.D. Shiltsev, D.A. Still, A. Valishev
Fermilab, Batavia, USA

Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. This work was partially supported by the US LHC Accelerator Research Program (LARP).
Recent experimental studies at the Tevatron collider have shown that magnetically confined hollow electron beams can act as a new kind of collimator for high-intensity beams in storage rings. In a hollow electron beam collimator, electrons enclose the circulating beam. Their electric charge kicks halo particles transversely. If their distribution is axially symmetric, the beam core is unaffected. This device is complementary to conventional two-stage collimation systems: the electron beam can be placed arbitrarily close to the circulating beam; and particle removal is smooth, so that the device is a diffusion enhancer rather than a hard aperture limitation. The concept was tested in the Tevatron collider using a hollow electron gun installed in one of the existing electron lenses. We describe some of the technical aspects of hollow-beam scraping and the results of recent measurements.

Slides WEODA02 [9.049 MB]

WEODA03

Design Concepts for the Large Hadron Electron Collider

linac, cavity, luminosity, collider

1942

M. Klein
The University of Liverpool, Liverpool, United Kingdom

A report is presented on the design concepts for a high luminosity electron-nucleon collider of 1.3 TeV centre of mass energy, realized with the addition of a 60 GeV electron ring or linear accelerator to the existing proton and ion LHC beam facility, comprising machine magnets, optics, interaction region, cryogenics, rf, civil engineering and further components of the LHeC. The report on behalf of the LHeC study team is a summary of the 2011 LHeC CDR and feedback received from an international review panel.

Slides WEODA03 [9.780 MB]

WEXB01

Advanced Acceleration Schemes

laser, plasma, acceleration, wakefield

1945

P.A. Naik, P.D. Gupta, B.S. Rao
RRCAT, Indore (M.P.), India

Review the progress and prospects of advanced acceleration concepts, including plasma acceleration, laser acceleration, and dielectric accelerators. Report ongoing and near-future experiments, and longer-term prospects for applications (e.g. compact X-ray sources, linear colliders, hadrontherapy).

Slides WEXB01 [8.636 MB]

WEOAB01

Highly Polarized and High Quantum Efficiency Electron Source Using Transmission-type Photocathode

laser, gun, brightness, polarization

1950

N. Yamamoto, F. Ichihashi, A. Mano, T. Nakanishi, Y. Takeda, T. Ujihara
Nagoya University, Nagoya, Japan
X.G. Jin
Institute for Advanced Research, Nagoya, Japan

The GaAs-type semiconductor photocathodes (PCs) with a negative electron affinity surface have been used as a polarized electron source and are expected as electron sources for next generation accelerators, such as Linear Colliders and Energy Recovery Linacs. Recently, we have developed transmission-type photocathodes (T-PCs).　By using T-PCs, polarized electron beam is extracted from the back-side of laser irradiation-side.　This scheme offers great merits in designing electron guns, such as short focusing of the laser light for a high brilliance electron beam and a simple geometrical structure avoiding an interference problem between the laser and the electron beam. The layer structure of the MOVPE-grown superlattice photocathode and the performance of 90% polarization, a super high brilliance, and a high quantum efficiency will be reported.

Slides WEOAB01 [6.007 MB]

WEOAB02

FACET: The New User Facility at SLAC

positron, plasma, linac, wakefield

1953

C.I. Clarke, F.-J. Decker, R.A. Erickson, C. Hast, M.J. Hogan, R.H. Iverson, S.Z. Li, Y. Nosochkov, N. Phinney, J. Sheppard, U. Wienands, W. Wittmer, M. Woodley, G. Yocky
SLAC, Menlo Park, California, USA
A. Seryi
JAI, Oxford, United Kingdom

Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
FACET (Facility for Advanced Accelerator and Experimental Tests) is a new User Facility at SLAC National Accelerator Laboratory. Its high power electron and positron beams make it a unique facility, ideal for beam-driven Plasma Wakefield Acceleration studies. The first 2 km of the SLAC linac produce 23 GeV, 3.2 nC electron and positron beams with short bunch lengths of 20 um. A final focusing system can produce beam spots 10um wide. User-aided Commissioning took place in summer 2011 and FACET will formally come online in early 2012. We present the User Facility, the current features, planned upgrades and the opportunities for further experiments.

Slides WEOAB02 [4.772 MB]

WEOAB03

The Production of High Quality Electron Beams in the ALPHA-X Laser Wakefield Accelerator

laser, plasma, emittance, radiation

1956

S.M. Wiggins, M.P. Anania, C. Aniculaesei, E. Brunetti, S. Cipiccia, B. Ersfeld, M.R. Islam, R.C. Issac, D.A. Jaroszynski, G.G. Manahan, R.P. Shanks, G.H. Welsh
USTRAT/SUPA, Glasgow, United Kingdom
W.A. Gillespie
University of Dundee, Nethergate, Dundee, Scotland, United Kingdom
A. MacLeod
UAD, Dundee, United Kingdom

Funding: The U.K. EPSRC, the EC's Seventh Framework Programme (LASERLAB-EUROPE / LAPTECH, grant agreement no. 228334) and the Extreme Light Infrastructure (ELI) project.
The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme is developing laser-plasma accelerators for the production of ultra-short electron beams as drivers of incoherent and coherent radiation sources from plasma and magnetic undulators. Here we report on the latest laser wakefield accelerator experiments on the University of Strathclyde ALPHA-X accelerator beam line looking at high quality electron beams. ALPHA-X uses a 26 TW Ti:sapphire laser (energy 900 mJ, duration 35 fs) focused into a helium gas jet (nozzle length 2 mm) to generate high quality monoenergetic electron beams with central energy in the range 80-180 MeV. The beam is fully characterized in terms of the charge, bunch length, energy spread and transverse emittance. The energy spectrum (with less than 1% measured energy spread) is obtained using a high resolution magnetic dipole imaging spectrometer while pepper-pot mask measurements show that the normalized transverse emittance is as low as 1.1 pi mm mrad (resolution limited). The conditions needed to obtain this high quality are discussed.

Slides WEOAB03 [2.904 MB]

WEOBB01

Sub-micrometer Resolution Transverse Electron Beam Size Measurement System based on Optical Transition Radiation

radiation, photon, background, extraction

1964

A.S. Aryshev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
S.T. Boogert, V. Karataev
JAI, Egham, Surrey, United Kingdom
D. Howell
Oxford University, Physics Department, Oxford, Oxon, United Kingdom

Optical Transition Radiation (OTR) appears when a charged particle crosses a boundary between two media with different dielectric properties has widely been used as a tool for transverse profile measurements of charged particle beams in numerous facilities worldwide. The resolution of the conventional monitors is defined by the Point Spread Function (PSF) dimension - the source distribution generated by a single electron and projected by an optical system onto a screen. For small electron beam dimensions, the PSF form significantly depends on various parameters of the optical system like diffraction of the OTR tails, spherical and chromatic aberrations, etc. In our experiment we managed to create a system which can practically measure the PSF distribution and using a new self-calibration method we are able to calculate transverse electron beam size. Here we represent the development, data analysis and novel calibration technique of a sub-micrometer electron beam profile monitor based on the measurements of the PSF shape, which OTR visibility is sensitive to micrometer electron beam dimensions.

Slides WEOBB01 [2.506 MB]

WEOBB02

Bunch Length Diagnostic with Sub-femtosecond Resolution for High Brightness Electron Beams

laser, undulator, simulation, cavity

1967

G. Andonian, E. Hemsing, P. Musumeci, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
A.Y. Murokh
RadiaBeam, Santa Monica, USA
D. Xiang
SLAC, Menlo Park, California, USA

Next generation light sources require electron beams with high peak currents, typically achieved by compression techniques. The temporal diagnosis of these ultra-short beams demands enhanced resolution. We describe a scheme to achieve a temporal resolution on the order of sub-femtoseconds. The scheme is based on encoding the longitudinal profile of the beam on a transverse angular modulation, based on an interaction between the electron beam and a high-power laser in an undulator. This imposes a fast-sweep of the beam, on the order of sub-femtoseconds. A subsequent sweep in the orthogonal dimension by an rf deflecting cavity, imposes a "slow-sweep" on the order of sub-picoseconds. In this paper, we demonstrate applicability of this diagnostic scheme at the BNL ATF and specify the techniques required for practical applicability.

Slides WEOBB02 [1.120 MB]

WEOBB03

Electron Bunch Profile Diagnostics in the Few fs Regime using Coherent Smith-Purcell Radiation

radiation, diagnostics, vacuum, linac

1970

N. Delerue
LAL, Orsay, France
R. Bartolini, G. Doucas, K. Pattle, C. Perry, A. Reichold, R. Tovey
JAI, Oxford, United Kingdom

Funding: John Fell Fund, University of Oxford
The rapid developments in the field of laser-driven particle acceleration hold the prospect of intense, highly relativistic electron bunches that are only a few fs long. The determination of the temporal profile of such a bunch presents new challenges. The use of a radiative process such as Smith-Purcell radiation (SPR), whereby the beam is made to radiate a small amount of e/m radiation and the temporal profile is then reconstructed from the measured spectral distribution of the radiation, is particularly promising in this respect. We summarize the advantages of SPR and present the design parameters of a forthcoming experiment at the FACET facility at SLAC with bunch lengths of the order of 60fs rms. We also discuss a new approach to the problem of the recovery of the ‘missing phase’, which is essential for the accurate reconstruction of the bunch profile.

Slides WEOBB03 [4.627 MB]

WEIB04

Accelertor-based Mega-science Projects in China and Their Impact on Economy

linac, vacuum, ion, radiation

1986

C. Zhang
IHEP Beijing, Beijing, People's Republic of China

Along with the rapid development of national economy in China, a number of accelerator based mega-science projects were constructed, such as the Beijing Electron-Positron Colliders (BEPC) and its major upgrade project (BEPCII), the Hefei Light Source (HLS), the Heavy Ion Research Facility in Lanzhou (HIRFL) and its Cooling Storage Rings (HIEFL-CSR), the Shanghai Synchrotron Radiation Facility (SSRF) and the Dragon-I induction linac. The Beijing Radioactive Ion Facility (BRIF) and the China Spallation Neutron Source (CSNS) are under construction. In this paper, China’s accelerator projects are briefly reviewed and applications of accelerators are reported. The paper emphasizes spinoff of the accelerator technology developed during R&D and construction of the projects. Collaboration between academia and industry on the projects are described. With some examples, the benefits experienced in the laboratory-industry collaboration and approach of its economic impact are illustrated.

Slides WEIB04 [14.012 MB]

WEIB05

Collaborative R&D in the Industry of Science

neutron, instrumentation, cyclotron, target

1991

C. Oyon
ESS, Lund, Sweden

Successful collaborative efforts involve committed partners that have established comforting level of trust. When industry and research laboratories establish such collaborations they create unique ecosystems that have potential to deliver creative solutions. Many times, however, those collaborations face unexpected legal and administrative limitations. The aim of this talk is to identify key limitations and suggest potential solutions that can streamline collaborative projects.

Slides WEIB05 [6.937 MB]

WEPC002

RF Separator and Septum Layout Concepts for Simultaneous Beams to RIB and FEL Users at ARIEL

septum, linac, dipole, FEL

1998

Y.-C. Chao, C. Gong, S.R. Koscielniak
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

A ½ MW capable CW electron linac is being designed and constructed at TRIUMF in support of the existing Rare Isotope Beam program. In the simplest configuration, the beam makes a single pass through three cryomodules to the RIB production targets. However, after the construction of a recirculation path, beam could make a second pass through two cryomodules with the RF phase advance adjusted to give energy recovery. Here it is proposed to time-interleave two bunch trains, and via an RF separator and septum, to direct one single-pass train to RIB production and the second train through the energy recovery ring that contains an IR FEL. It is also the intention, in single user mode, to use the ring as an energy doubler. This paper describes the RF separation scheme and options for the extraction optics that satisfy the requirements of “simultaneous” beams to two users.

WEPC006

Upgrade Plans on the Superconducting Electron Accelerator S-DALINAC

recirculation, linac, dipole, extraction

2010

M. Kleinmann, R. Eichhorn, F. Hug, N. Pietralla
TU Darmstadt, Darmstadt, Germany

Funding: Work supported by DFG through SFB 634
The S-DALINAC is a superconducting recirculating electron accelerator with maximum design energy of 130 MeV operating in cw at 3 GHz. Even so the gradients of the superconducting cavities are well above design, their design quality factor of 3*10⁹ have not been reached so far, leading to higher heat transfer into the liquid helium than expected. Due to the limited cooling power of the cryo-plant being 120 W, the final energy achievable in cw operation is around 85 MeV, currently. In order to provide a cw beam with the designed final energy in the future, the installation of an additional recirculation path is projected. We will report on the beam-line and the magnet design for the new recirculation path. In addition, we will present the layout of two proposed scraper-systems which will be used to remove the halo of the electron beam allowing high precision coincidence experiments with very low background for nuclear physics in the future.

WEPC018

Self-focusing Effects in Compact C-band Standing-wave Accelerating Structure for X-ray Imaging Applications

focusing, bunching, accelerating-gradient, linac

2046

H.R. Yang, M.-H. Cho, S.H. Kim, W. Namkung, S.J. Park
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.-S. Oh
NFRI, Daejon, Republic of Korea

In electron RF linacs for industrial X-ray imaging applications, compact structures are preferred for mobility. The electron beam spot size of 1 – 2 mm is required for the spatial resolution of images at the X-ray conversion target. Applying self-focusing effects to the accelerating structure, external magnets can be removed and then the accelerator system becomes more compact. We design a C-band electron linac, which is capable of producing 6-MeV, 80-mA pulsed electron beams with an RF power of 1.5 MW. It uses a bi-periodic and on-axis-coupled accelerating structure with a built-in bunching section. It uses the π/2-mode standing-waves. The first bunching cell has an asymmetric geometry which maximizes the RF phase focusing. On the other hand, the normal cells are designed for the electrostatic focusing to be maximized. In this paper, we present design details of the accelerating cells and the beam dynamics simulation by the PARMELA code.

WEPC045

Transverse Emittance Reduction with Tapered Foil

emittance, scattering, target, simulation

2112

Y. Jiao, Y. Cai, A. Chao
SLAC, Menlo Park, California, USA

Funding: The work is supported by the U.S. Department of Energy under contract No. DE-AC02-76SF00515.
The idea of reducing transverse emittance with tapered energy-loss foil is proposed by J.M. Peterson in 1980s and recently by B. Carlsten. In present paper, we present the physical model of tapered energy-loss foil and analyze the emittance reduction using the concept of eigen emittance. The study shows that, to reduce transverse emittance, one should collimate at least 4% of particles which has either much low energy or large transverse divergence. The multiple coulomb scattering is not trivial, leading to a limited emittance reduction ratio.

WEPC047

Crab Crossing Schemes and Studies for Electron Ion Collider

cavity, collider, lattice, ion

2115

S. Ahmed, S.U. De Silva, Y.S. Derbenev, G.A. Krafft, V.S. Morozov, B.C. Yunn, Y. Zhang
JLAB, Newport News, Virginia, USA
A. Castilla, J.R. Delayen
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Medium Energy Electron Ion Collider (MEIC) at JLab has been envisioned as future high energy particle accelerator beyond 12 GeV upgrade of CEBAF. Crab crossing of colliding electron and ion beams is essential for accommodating high bunch repetition frequency in the conceptual design of MEIC. The scheme eliminates parasitic beam-beam interactions and avoids luminosity reduction by restoring head-on collisions at interaction points. This requires the separation of two beams quickly to avoid parasitic collisions and the minimization of synchrotron-betatron resonance near IP which can be fulfilled by employing the crab crossing concept first proposed by R. Palmer. Let us call this original scheme as transverse crabbing for the sake of comparison with dispersive crabbing which employs the existing accelerating/bunching RF cavities and dispersion function in the section where the cavity is installed as originally proposed by G. Jackson. In this paper, we report the beam transport and optics for both transverse and dispersive crabbing schemes followed by basic beam dynamics. Moreover, alignment and stability calculations together with synchro-betatron beam dynamics will be discussed.

WEPC051

Effect of Compton Scattering on the Electron Beam Dynamics at the ATF Damping Ring

scattering, laser, damping, cavity

2127

I. Chaikovska, C. Bruni, N. Delerue, A. Variola, Z.F. Zomer
LAL, Orsay, France
K. Kubo, T. Naito, T. Omori, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Compton scattering provides one of the most promising scheme to obtain polarized positrons for the next generation of e⁺e⁻ colliders. Moreover it is an attractive method to produce monochromatic high energy polarized gammas for nuclear applications and X-rays for compact light sources. In this framework a four-mirror Fabry-Perot cavity has been installed at the Accelerator Test Facility (ATF - KEK, Tsukuba, Japan) and will be used to produce an intense flux of polarized gamma rays by Compton scattering. For electrons at the energy of the ATF (1.28GeV) Compton scattering may result in a shorter lifetime due to the limited bucket acceptance. We have implemented the effect of Compton scattering on a 2D tracking code with a Monte-Carlo method. This code has been used to study the longitudinal dynamics of the electron beam at the ATF damping ring, in particular the evolution of the energy spread and the bunch length under Compton scattering. The results obtained are presented and discussed. Possible methods to observe the effect of Compton scattering on the ATF beam are proposed.

WEPC053

Crossing of Depolarizing Resonances in Circular Electron Accelerators

resonance, polarization, closed-orbit, quadrupole

2133

W. Hillert, A. Balling, O. Boldt, A. Dieckmann, F. Frommberger
ELSA, Bonn, Germany

Funding: Supported by the German Research Foundation (DFG) through SFB/TR 16
In flat electron storage rings, only the vertical component of the beam polarization is preserved. During acceleration, the crossing of several depolarizing resonances may cause severe beam depolarization. Even in case of fast ramping speeds of up to 6 GeV/sec, first order effects like imperfection and intrinsic resonances have to be compensated by dedicated measures. At the accelerator facility ELSA, schemes like fast tune jumping and harmonic orbit correction are successfully applied on the fast energy ramp up to 3.2 GeV. Characteristics of the setup as well as the optimization efforts to improve the resonance compensation will be reported in detail.

WEPC061

ENC Interaction Region Separation Dipoles

dipole, solenoid, sextupole, multipole

2157

P. Schnizer, E.S. Fischer
GSI, Darmstadt, Germany
K. Aulenbacher
IKP, Mainz, Germany

The Electron Nucleon Collider (ENC) is proposed as an upgrade of the High Energy Storage Ringe of the FAIR. The beams are separated by two dipoles, mounted closely to the intraction point; surrounded by the detectors. Hence these magnetsmust provide sufficient field quality but be slim to be transparaent to the secondary particles. Further these must be air coil magnets due to the detector solenoid field of 2T. We present the 3D optimised magnet next to a first design of the mechanical restraint structure and a concise description for the field distortion leaking into the detector.

WEPC071

The Motion of an Electron in the Periodic Cusped Magnetic Fields

wiggler, focusing, betatron, coupling

2184

G. Du, B.L. Qian, H. Wang
National University of Defense Technology, Changsha, Kaifu District, People's Republic of China

Funding: National High Technology Research and Development Program of P. R. China
The motion and its stability of an electron in the periodic cusped magnetic fields have been analyzed theoretically and calculated numerically, as the stability could not be well predicted by the Mathieu’s equation to guide the design of the magnetic focusing system for the propagation of the sheet electron beams in the waveguides. The precise solution to the motion equations of the electron has been obtained by iteration. To validate the analytical solution and to evaluate the stability of the motion, numerical calculations have been carried out. And the results show that the analytical solution is reliable, and there is only one stable region in the (p₀, B₀) space, where the parameter p₀ is the period of the magnetic fields, and B₀ is the magnitude of the magnetic fields. Besides, the stability of the electron motion would become weaker while the initial distance between the electron and the axis becomes larger. These results are interesting to the area of the sheet-electron-beam microwave sources focused by the periodical cusped magnetic fields.

WEPC087

Dark Current Simulations for the Cornell ERL

cavity, linac, simulation, cryomodule

2214

C.E. Mayes, C.S. Chiu, G.H. Hoffstaetter, V.O. Kostroun, D. Sagan
CLASSE, Ithaca, New York, USA
L.M. Nash
North Carolina University, Chapel Hill, North Carolina, USA

Funding: Supported by NSF award DMR-0807731
Charged particles unintentionally transported through an accelerator, collectively called the dark current, can be lost in the beam chamber and create a radiation hazard for both equipment and personnel. Here we simulate the creation of particles by field emission in the superconducting accelerating cavities of the Cornell Energy Recovery Linac, and track them to their loss points. These lost particles can then be used to simulate background radiation. The presented calculations are therefore an essential step in the design of appropriate radiation-shielding of components around the linac.

WEPC088

Embedding Finite Element Results for Accelerator Components in a Moment Approach Beam Dynamics Code*

quadrupole, simulation, dipole, sextupole

2217

T. Roggen, H. De Gersem, B. Masschaele
KU Leuven, Kortrijk, Belgium
W. Ackermann, S. Franke, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: This research is funded by grant ''KUL 3E100118'' ''Electromagnetic Field Simulation for Future Particle Accelerators''.
A moment based beam dynamics code has particular advantages, i.e. accuracy and efficiency, over macro-particle tracking and full particle-in-cell (PIC) codes respectively. Instead of embedding analytical descriptions of the accelerator components in the beam dynamics model, it is proposed to insert a surrogate model obtained from the finite element model of individual accelerator components. We apply the V-Code, which accepts moments up to the sixth order and accounts for space charge effects. We construct and calculate finite element and finite difference time domain models using the CST Studio Suite 2011 software package. An interface is implemented using VBA and MATLAB. As an example of the accuracy of this cascadic simulation approach, we compare the beam dynamics of an S-DALINAC quadrupole obtained by directly tracking particles to the calculated fields with the results for the cascadic approach with the V-Code.
This work was performed during a three month research visit at the Technische Universität Darmstadt, Institut für Theorie Elektromagnetischer Felder, Darmstadt, Germany.

WEPC094

Energy Loss and Longitudinal Wakefield of Relativistic Short Ion Bunches in Electron Clouds

simulation, ion, wakefield, plasma

2229

F. Yaman, O. Boine-Frankenheim, E. Gjonaj, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany
G. Rumolo
CERN, Geneva, Switzerland

Funding: Work supported by BMBF under contract 06DA9022I
The aim of our study is the numerical computation of the wakefield, impedance and energy loss for an energetic, short (< 10 ns) ion bunch penetrating an electron cloud plasma residing in the beam pipe. We use a 3-D self-consistent and higher order PIC code based on the full-wave solution of the Maxwell equations in the time domain. In our simulations we observe the induced density oscillations in the electron cloud in the longitudinal as well as in the transverse directions. A special numerical procedure is applied to compute the longitudinal wake potential and the broadband coupling impedance due to the beam-electron cloud interaction. The code is applied to the case of the CERN SPS and the projected SIS-100 at GSI. The effects of the beam pipe, electron density, bunch intensity and external magnetic dipole fields are studied. The results are compared to analytical and numerical models of reduced complexity.

WEPC095

Simulations of the Microbunching Instability at ANKA using a Vlasov-Fokker-Planck Solver

radiation, synchrotron, simulation, impedance

2232

M. Klein, A.-S. Müller
KIT, Karlsruhe, Germany
K.G. Sonnad
CLASSE, Ithaca, New York, USA

In order to produce coherent synchrotron radiation the ANKA light source is operated frequently in short bunch mode. It is known that during this procedure strong self fields caused by high electron densities can enforce initial density fluctuations and thus lead to microbunching. The build-up of those substructures is accompanied by bursting radiation which provides higher radiation power for the users. Damping and diffusion due to incoherent radiation smoothens the bunch shape again and hence lead to periodic or chaotic bursting cycles. The evolution of the electron bunch density under the influence of self fields can be described by the Vlasov-Fokker-Plank (VFP) equation. We present results from a numerical solution of the VFP-equation for parameters used in standard short bunch mode at ANKA.

WEPC100

Simulation of the Single Bunch Instability due to the Electron Cloud Effect by Tracking with a Pre-computed 2D Wake Matrix*

dipole, simulation, single-bunch, positron

2247

A. Markoviḱ, G. Pöplau, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany

Funding: Supported by DFG Contract Nr. RI 814/20-1.
The passage of a positron bunch through an initially homogeneous electron cloud (e-cloud) changes the distribution of the e-cloud in a way that the concentration of electrons in the proximity of the beam axis grows rapidly. The electrons are primarily moving in the transverse plane and are very sensitive on the beam centroid position in that plane. Thus the transverse kick of the e-cloud on the tail particles depends on the centroid position of the head particles of the same bunch. A PIC simulation of the interaction of a positron beam with an e-cloud yields the wake kick from the electrons on the tail particles for a certain offset in the transverse centroid position of the head parts of the bunch. With such a pre-computed 2D wake matrix, for a certain e-cloud density, we investigate the stability of a single bunch by tracking it through the linear optics of the storage ring while at each turn applying the kick from the e-cloud. We examine the positron bunch stability of KEKB-LER and PETRAIII for a certain electron cloud density.

WEPC101

Simulation of the Interaction of an Electron Beam with Ionized Residual Gas

ion, simulation, space-charge, emittance

2250

G. Pöplau, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
A. Meseck
HZB, Berlin, Germany

Funding: Supported by BMBF under contract number 05K10HRC
Light sources of the next generation such as ERLs require minimal beam losses as well as a stable beam position and emittance over the time. Instabilities caused by ion accumulation have to be avoided. In Rostock the tracking code MOEVE PIC Tracking has been developed for the simulation of space charge influenced beam dynamics, which is recently applied for simulations of the interaction beam - e-cloud. In this paper we apply MOEVE PIC Tracking for simulation of the interaction of the ionized residual gas with an electron bunch. We demonstrate numerical results with parameters planed for the ERL BERLinPro.

WEPC132

Simulations of Surface Effects and Electron Emission from Diamond-Amplifier Cathodes

simulation, vacuum, scattering, cathode

2307

D.A. Dimitrov, R. Busby, J.R. Cary, D.N. Smithe
Tech-X, Boulder, Colorado, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
X. Chang, T. Rao, J. Smedley, Q. Wu
BNL, Upton, Long Island, New York, USA
E. Wang
PKU/IHIP, Beijing, People's Republic of China

Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under grants DE-SC0004431 (Tech-X Corp.), DE-AC02-98CH10886 (BNL), and DE-SC0005713 (Stony Brook University).
Emission of electrons in diamond experiments based on the promising diamond-amplifier concept* was recently demonstrated**. Transmission mode experiments have shown the potential to realize over two orders of magnitude charge amplification. However, the recent emission experiments indicate that surface effects should be understood in detail to build cathodes with optimal properties. We have made progress in understanding secondary electron generation and charge transport in diamond with models we implemented in the VORPAL particle-in-cell computational framework. We will introduce models that we have been implementing for surface effects (band bending and electron affinity), charge trapping, and electron emission from diamond. Then, we will present results from 3D VORPAL diamond-vacuum simulations with the integrated capabilities on generating electrons and holes, initiated by energetic primary electrons, charge transport, and then emission of electrons from diamond into vacuum. Finally, we will discuss simulation results on the dependence of the electron emission on diamond surface properties.
* I. Ben-Zvi et al., Secondary emission enhanced photoinjector, C-AD Accel. Phys. Rep. C-A/AP/149, BNL (2004).
** X. Chang et al., Phys. Rev. Lett. 10⁵, 164801 (2010).

WEPC135

Recent Developments in Modeling Time-resolved Shielded-pickup Measurements of Electron Cloud Buildup at CESRTA

vacuum, radiation, pick-up, photon

2313

J.A. Crittenden, Y. Li, X. Liu, M.A. Palmer, J.P. Sikora
CLASSE, Ithaca, New York, USA
R.P. Badman
Syracuse University, Syracuse, USA
S. Calatroni, G. Rumolo
CERN, Geneva, Switzerland
S. Kato
KEK, Ibaraki, Japan

Funding: Work supported by the U.S. National Science Foundation PHY-0734867, PHY-1002467 and the U.S. Department of Energy DE-FC02-08ER41538
The Cornell Electron Storage Ring Test Accelerator program includes investigations into the mitigation of electron cloud buildup using a variety of techniques in custom vacuum chambers. The CESR ring accommodates two such chambers equipped with BPM-style pickup detectors shielded against the direct beam-induced signal. The signals provide time-resolved information on cloud development. Results for diamond-like carbon, amorphous carbon, and TiN coatings have been compared to those for an uncoated aluminum chamber. Here we report on extensions to the ECLOUD modeling code which refine its description of a variety of new types of in situ vacuum chamber comparisons. Our results highlight the sensitivity afforded by these measurements to the modeled photoelectron production and secondary yield parameters. We draw conclusions comparing the photoelectron and secondary yield properties of the various vacuum chamber coatings, including conditioning effects as a function of synchrotron radiation dose. We find substantial conditioning effects in both the quantum efficiency for producing photoelectrons and in the secondary yield.

WEPC137

Undulator Radiation Simulation by QUINDI

undulator, radiation, simulation, polarization

2316

D. Schiller, E. Hemsing, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

QUINDI, a code developed to simulate coherent emission from bending systems, has been upgraded to include undulators as a beamline element. This approach allows us to better model the radiation produced by a relativistic electron bunch propagating through such a device.

WEPC141

Application of the SYNRAD3D Photon-Tracking Model to Shielded Pickup Measurements of Electron Cloud Buildup at CesrTA

photon, scattering, simulation, vacuum

2319

L.E. Boon
Purdue University, West Lafayette, Indiana, USA
J.A. Crittenden, T. Ishibashi
CLASSE, Ithaca, New York, USA
K.C. Harkay
ANL, Argonne, USA

Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
We present calculations of synchrotron radiation photon reflection in the vacuum chamber at the Cornell Electron Storage Ring Test Accelerator (CesrTA), applying them as input to the electron cloud buildup code ECLOUD to model time-resolved local measurements with shielded pickup detectors. The recently developed SYNRAD3D photon-tracking code employs a reflection model based on data from the Center for X-Ray Optics at LBNL. This study investigates the dependence of electron cloud buildup on the azimuthal position and kinetic energy distribution of photoelectron production on the vacuum chamber wall.

WEPC143

First Operation of the SACLA Control System in SPring-8

controls, laser, monitoring, status

2325

R. Tanaka, Y. Furukawa, T. Hirono, M. Ishii, M. Kago, A. Kiyomichi, T. Masuda, T. Matsumoto, T. Matsushita, T. Ohata, C. Saji, T. Sugimoto, M. Yamaga, A. Yamashita
JASRI/SPring-8, Hyogo-ken, Japan
T. Fukui, T. Hatsui, N. Hosoda, T. Ohshima, T. Otake, Y. Otake, H. Takebe
RIKEN/SPring-8, Hyogo, Japan
H. Maesaka
RIKEN Spring-8 Harima, Hyogo, Japan

The control system design of the X-ray free electron laser facility (SACLA) in SPring-8 has started in 2006. Now, the facility has completed to start beam commissioning in February 2011. The electron beams were successfully accelerated up to 8 GeV and the first SASE X-ray was observed. The control system adopts the 3-tier standard model by using MADOCA framework developed in SPring-8. The upper control layer consists of Linux PCs for operator consoles, Sybase RDBMS for data logging and FC-based NAS for NFS. The lower layer consists of VMEbus systems with off-the-shelf I/O boards and specially developed boards for RF waveform processing with high precision. Solaris OS is adopted to operate VMEbus CPU. The PLC is used for slow control and connected to the VME systems via FL-net. The Device-net is adopted for frontend device control to reduce the number of signal cables. Some of VMEbus systems have a beam-synchronized data-taking system to meet 60Hz electron beam operation for the beam tuning diagnostics. The accelerator control system has gateways not only to monitor device status but also control the tuning points of the facility utility system, especially cooling water.

WEPC164

First Operation of a Fiber Beam Loss Monitor at the SACLA FEL

undulator, beam-losses, vacuum, radiation

2367

X.-M. Maréchal, T. Itoga
JASRI/SPring-8, Sayo-gun, Japan
Y. Asano
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

A fiber-based Cerenkov beam loss monitor (CBLM) has been developed as a quick and long-range detection tool for radiation safety at the X-ray FEL SACLA (SPring-8 angstrom compact free electron laser) to minimize electron beam losses. Based on tests carried out at the 250 MeV SPring-8 Compact SASE Source facility, large core (400 μm), long (>120 m) multimode fibers were selected and installed in the undulator section of SACLA. We report on the first few months of operation of the CBLM. During the commissioning of the X-FEL, the CBLM has performed effectively, with a detection limit below 10 pC per pulse across the 110 meters of the in-vacuum undulators, and with a position accuracy of less than 2 m. Experimental results are presented along with detailed numerical studies including the geometry of in-vacuum insertion devices, and discussed.

WEPC169

BPM System Interlock for Machine Protection at SOLEIL

photon, undulator, vacuum, power-supply

2379

J.-C. Denard, C. Herbeaux, M. Labat, V. Leroux, A. Loulergue, J.L. Marlats
SOLEIL, Gif-sur-Yvette, France

SOLEIL, a third generation light source, has its Beam Position Monitors (BPM) processed by the LIBERA electronics built by Instrumentation Technologies. This electronics initiated and specified by SOLEIL features a fast hardware interlock output for machine protection. Although interlocks are available in both horizontal and vertical planes, it was initially thought that only the vertical interlocks would be useful. Actually, the high photon beam power densities (up to 1kW/mm2) generated by the in-vacuum undulators could damage vacuum chamber elements in case of corrector power supply failures in horizontal or vertical plane. Crotch absorbers, XBPMs and their upstream absorbers were designed on the basis that they will be protected with interlock thresholds not tighter than ±1mm. This approach was also applied for specifying the apertures of the XBPMs and of their upstream absorbers. More recently tracking simulation has shown that the crotch absorber apertures downstream the new canted undulators needed special attention.

WEPC173

LHC Magnet Quench Test with Beam Loss Generated by Wire Scan

beam-losses, proton, simulation, quadrupole

2391

M. Sapinski, F. Cerutti, K. Dahlerup-Petersen, B. Dehning, J. Emery, A. Ferrari, A. Guerrero, E.B. Holzer, M. Koujili, A. Lechner, E. Nebot Del Busto, M. Scheubel, J. Steckert, A.P. Verweij, J. Wenninger
CERN, Geneva, Switzerland

Beam losses with millisecond duration have been observed in the LHC in 2010 and 2011. They are expected to be provoked by dust particles falling into the beam. These losses could compromise the LHC availability if they provoke quenches of superconducting magnets. In order to investigate the quench limits for this loss mechanism, a quench test using the wire scanner has been performed, with the wire movement through the beam mimicking a loss with similar spatial and temporal distribution as in the case of dust particles. This paper will show the conclusions reached for millisecond-duration dust-provoked quench limits. It will include details on the maximum energy deposited in the coil as estimated using FLUKA code, showing good agreement with quench limit estimated from the heat transfer code QP3. In addition, information on the damage limit for carbon wires in proton beams will be presented, following electron microscope analysis which revealed strong wire sublimation.

WEPO003

The FERMI@Elettra Magnets

dipole, quadrupole, gun, FEL

2409

D. Castronovo, R. Fabris, G.L. Loda, D. Zangrando
ELETTRA, Basovizza, Italy

FERMI@Elettra is a single-pass FEL user-facility located next to the third generation synchrotron radiation facility ELETTRA in Trieste, Italy. The linear accelerator contains more than 200 magnets. This paper reports on the design, construction, magnetic measurement and installation.

WEPS004

Confinement, Accumulation and Diagnostic of Low Energy Ion Beams in Toroidal Fields

ion, diagnostics, beam-transport, injection

2487

M. Droba, A. Ates, O. Meusel, H. Niebuhr, U. Ratzinger, J.F. Wagner
IAP, Frankfurt am Main, Germany

An optimized design of a stellarator-type storage ring for low energy ion beams was numerically investigated. The magnetic field variation along the circumference and therefore magnetic heating is suppressed by using simple circular correction coils. Particle-in-Cell (PIC) simulations in a magnetic flux coordinate system show the ability of high current ion beam accumulation in such a configuration with unique features for clockwise and anticlockwise moving beams. Additionally scaled down experiments with two 30 degree room temperature toroidal segments were performed to demonstrate toroidal transport and to develop optical beam diagnostics. Properties of multi-component beams, redistribution of transversal momenta in the non-adiabatic part of the experimental configuration and investigation of strongly confined beam induced electron clouds will be addressed.

WEPS005

Investigation of Intrabeam Scattering in the Heavy Ion Storage Ring TSR

ion, bunching, scattering, storage-ring

2490

S.T. Artikova, M. Grieser, J. Ullrich
MPI-K, Heidelberg, Germany

Intrabeam scattering (IBS) is a multiple scattering effect between stored beam particles. It leads to diffusion in all three spatial dimensions and thus, causes an expansion of the whole beam. IBS plays an important role in the equilibrium diameter of a low-velocity, electron-cooled ion beam. IBS effects for coasting and bunched 12C⁶⁺ ion beams at an energy of 73.3 MeV were studied using the TSR heavy ion cooler storage ring. Experimental results of the IBS rates are presented.

WEPS017

Plans for the Upgrade of the LHC Injectors

linac, injection, synchrotron, booster

2517

R. Garoby, S.S. Gilardoni, B. Goddard, K. Hanke, M. Meddahi, M. Vretenar
CERN, Geneva, Switzerland

The LHC Injectors Upgrade (LIU) project has been launched at the end of 2010 to prepare the CERN accelerator complex for reliably providing beam with the challenging characteristics required by the high luminosity LHC until at least 2030. Based on the work already started on Linac4, PS Booster, PS and SPS, the LIU project coordinates studies and implementation, and interfaces with the High Luminosity LHC (HL-LHC) project which looks after the upgrade of the LHC itself, expected by the end of the present decade. The anticipated beam characteristics are described, as well as the status of the studies and the solutions envisaged for improving the injector performances.

WEPS018

The Proposed CERN Proton-Synchrotron Upgrade Program

injection, emittance, cavity, space-charge

2520

S.S. Gilardoni, S. Bart Pedersen, W. Bartmann, S. Bartolome, O.E. Berrig, C. Bertone, A. Blas, D. Bodart, J. Borburgh, R.J. Brown, A.C. Butterworth, M.C.L. Buzio, C. Carli, P. Chiggiato, H. Damerau, T. Dobers, R. Folch, R. Garoby, B. Goddard, M. Gourber-Pace, S. Hancock, M. Hourican, P. Le Roux, L.A. Lopez Hernandez, A. Masi, G. Metral, Y. Muttoni, E. Métral, M. Nonis, J. Pierlot, S. Pittet, C. Rossi, I. Ruehl, G. Rumolo, L. Sermeus, R.R. Steerenberg, M. Widorski
CERN, Geneva, Switzerland

In the framework of the High-Luminosity LHC project, the CERN Proton Synchrotron would require a major upgrade to match the future beam parameters requested as pre-injector of the collider. The different beam dynamics issues, from space-charge limitations to longitudinal instabilities are discussed, as well as the proposed technical solutions to overcome them, covering the increase of the injection energy to RF related improvements.

WEPS033

Matching a Laser Driven Proton Injector to a CH - Drift Tube Linacs

proton, laser, solenoid, acceleration

2556

A. Almomani, M. Droba, U. Ratzinger
IAP, Frankfurt am Main, Germany
I. Hofmann
HIJ, Jena, Germany

Experimental results and theoretical predictions in laser acceleration of protons achieved energies of ten to several tens of MeV. The LIGHT project (Laser Ion Generation, Handling and Transport) is proposed to use the PHELIX laser accelerated protons and to provide transport, focusing and injection into a conventional accelerator. This study demonstrates transport and focusing of laser-accelerated 10 MeV protons by a pulsed 18 T magnetic solenoid. The effect of co-moving electrons on the beam dynamics is investigated. The unique features of the proton distribution like small emittances and high yield of the order of 10¹3 protons per shot open new research area. The possibility of creating laser based injectors for ion accelerators is addressed. With respect to transit energies, direct matching into DTL's seems adequate. The bunch injection into a proposed CH⁻ structure is under investigation at IAP Frankfurt. Options and simulation tools are presented.

WEPS079

Serpentine Acceleration in Scaling FFAG

acceleration, injection, proton, closed-orbit

2691

E. Yamakawa, Y. Ishi, Y. Kuriyama, J.-B. Lagrange, Y. Mori, R. Nakano, T. Planche, B. Qin, T. Uesugi
KURRI, Osaka, Japan
K. Okabe, I. Sakai
University of Fukui, Faculty of Engineering, Fukui, Japan

A serpentine acceleration in scaling FFAG accelerator has been examined. In this scheme, high-energy and high-current beam can be obtained in non-relativistic energy region. Longitudinal hamiltonian is also derived analytically.

WEPZ005

Field Calculations to obtain Attosecond/Femtosecond Electron Bunches

cathode, laser, injection, radiation

2772

V.A. Papadichev
LPI, Moscow, Russia

Obtaining short electron bunches of attosecond and femtosecond duration in a combined quasi-static and laser electric field [* - ****] requires careful field formation in the cathode region. First, the maximum of laser electric field normal to the cathode plate, depending on the incidence angle, was found employing Fresnel formulae using complex dielectric permittivity of metals. Second, laser field enhancement on cathode spikes was calculated for the case of an ellipsoid in a qusi-static approximation (laser wavelength larger than spike dimensions). Field enhancement is approximately proportional to the square of the ratio of major to minor axes of ellipsoid. Thus, enhancement factors as large as 100 - 1000 are obtainable, allowing to reduce laser power by 10 thousand to 1 million times.
* V.A.Papadichev, Patent RU 2 269 877 C1, 10.02.06, Bull. 4.
** V.A.Papadichev, Proc. EPAC08, p.2812.
*** V.A.Papadichev, Proc. EPAC08, p.2815.
**** V.A.Papadichev, Proc. IPAC'10, p. 4372

WEPZ006

Forming Attosecond Electron Pulses in Space-charge Dominated Regime

radiation, laser, acceleration, bunching

2775

V.A. Papadichev
LPI, Moscow, Russia

Production of high-current attosecond electron pulses requires studying of the final bunching stage, which inevitably is space-charge dominated [*, **, ***]. Two models are studied, both allow solving a one-dimensional equation of motion. The first is for a spherical bunch, which corresponds to a short emitted pulse from a one-spike cathode of diameter approximately equal to its length. The second model is suited for pulses emitted from a multi-spike or multi-blade cathode. The bunch in the latter case is a thin plate and its evolution can be studied by also solving one-dimensional equation of motion. It was shown that bunches of 10-attosecond (as) duration with peak current of dozens of amperes can be obtained when using a carbon dioxide laser and less than 0.1-as duration with currents up to 1 MA when employing a neodymium laser. Beam focusing in transverse directions is also studied using a model. Possible applications of such electron bunches are reviewed, including obtaining attosecond pulses of tunable coherent radiation in UV and X-ray regions.
* V.A.Papadichev, Proceedings of EPAC08, p.2815.
** V.A.Papadichev, Proceedings of IPAC'10, Kyoto, Japan, p. 4372.
*** V.A.Papadichev, Proc. RUPAC-2010, TUPSAO10, p. 56.

WEPZ008

Experimental Plans to Explore Dielectric Wakefield Acceleration in the THz Regime

wakefield, acceleration, simulation, dipole

2781

F. Lemery, D. Mihalcea, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
C. Behrens, E. Elsen, K. Flöttmann, C. Gerth, G. Kube, B. Schmidt
DESY, Hamburg, Germany
J. Osterhoff
LBNL, Berkeley, California, USA
P. Stoltz
Tech-X, Boulder, Colorado, USA

Funding: This work was supported by the Defense Threat Reduction Agency, Basic Research Award \# HDTRA1-10^-1-0051, to Northern Illinois University
Dielectric wakefield accelerators have shown great promise toward high-gradient acceleration. We investigate tow experiments in preparation to explore the performance of cylindrically-symmetric and slab-shaped dielectric-loaded waveguides. The planned experiments at Fermilab and DESY will use unique pulse shaping capabilities offered at these facilities. The superconducting test accelerator at FNAL will ultimately provide flat beams with variable current profiles needed for enhancing the transformer ratio. The FLASH facility at DESY recently demonstrated the generation of a ramped round beam current profile that will enable us to explore the performance of cylindrically-symmetric structures. Finally both of these facilities incorporate superconducting linear accelerator that could generate bunch trains with closely spaced bunches thereby opening the exploration of dynamical effects in dielectric wakefield accelerators. We present the planned layout and simulated experimental performances.

WEPZ010

Modeling and Experimental Update on Direct Laser Acceleration

laser, plasma, acceleration, simulation

2787

I. Jovanovic, M.W. Lin
Penn State University, University Park, Pennsylvania, USA

Funding: This work is supported by the Defense Threat Reduction Agency under contract HDTRA1-11-1-0009.
Moderate-energy, high-repetition-rate electron beams are needed in a variety of applications such as those in security and medicine, while requiring that the acceleration be realized in a compact and relatively inexpensive package. Laser wakefield acceleration is an attractive technology which meets most of those requirements, but it requires the use of relatively high peak power lasers which do not scale readily to high repetition rates. We are developing the theoretical and experimental basis for advancing the science and technology of direct laser acceleration (DLA) of charged particles using the axial component of the electric field of a radially polarized intense laser pulse. DLA is an acceleration method which exhibits no threshold and is thus compatible with the use of lower peak power, but much higher repetition rate lasers. We are currently numerically investigating the conditions for quasi-phase-matched DLA of electrons in plasma waveguides and experimentally implementing the quasi-phase-matched waveguide structure in laser-produced plasmas.

WEPZ011

Fast Cooling of Bunches in Compton Storage Rings

laser, emittance, scattering, photon

2790

E.V. Bulyak
NSC/KIPT, Kharkov, Ukraine
J. Urakawa
KEK, Ibaraki, Japan
F. Zimmermann
CERN, Geneva, Switzerland

We propose an enhancement of laser radiative cooling by utilizing laser pulses of small spatial and temporal dimensions, which interact only with a fraction of an electron bunch circulating in a storage ring. We studied the dynamics of such electron bunch when laser photons scatter off the electrons at a collision point placed in a section with nonzero dispersion. In this case of ‘asymmetric cooling', the stationary energy spread is much smaller than under conditions of regular scattering where the laser spot size is larger than the electron beam; and the synchrotron oscillations are damped faster. Coherent oscillations of large amplitude may be damped within one synchrotron period, so that this method can support the rapid successive injection of many bunches in longitudinal phase space for stacking purposes. Results of extensive simulations are presented for the performance optimization of Compton gamma-ray sources and damping rings.

WEPZ013

Design Status of LHeC Linac-Ring Interaction Region

proton, quadrupole, optics, dipole

2796

R. Tomás, J.L. Abelleira, S. Russenschuck, F. Zimmermann
CERN, Geneva, Switzerland
N.R. Bernard
UCLA, Los Angeles, California, USA

The ECFA-CERN-NuPECC design study for a Large Hadron electron Collider (LHeC) based on the LHC, considers two options, using a ring accelerator like LEP on top of the LHC or adding a recirculating energy-recovery linac tangential to the LHC. In order to obtain the required luminosity with an e^- beam from a linac, with average lepton beam current limited to a few mA, reaching the smallest possible proton beam size is essential. Another constraint is imposed by the need to separate e^- and p beams after the collision without losing too much luminosity from a crossing angle. A further constraint is that the ep collision should occur simultaneously to pp collisions at other LHC interaction points such that the second LHC proton beam must be accommodated in the interaction region too. We present a conceptual layout using detector-integrated combination-separation dipoles and challenging Nb3Sn technology quadrupoles for focusing the colliding proton beam and providing a low-field “hole” to accommodate both the non-colliding proton beam and the lepton beam, and the optics for all three beams. We discuss synchrotron radiation fluxes and the chromatic correction for the lepton final focus.

WEPZ014

Upgrade of the Argonne Wakefield Accelerator Facility (AWA): Commissioning of the RF Gun and Linac Structures for Drive Beam Generation

wakefield, gun, linac, acceleration

2799

M.E. Conde, D.S. Doran, W. Gai, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof
ANL, Argonne, USA
S.P. Antipov, C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Research at the AWA Facility has been focused on the development of electron beam driven wakefield structures. Accelerating gradients of up to 100 MV/m have been excited in dielectric loaded cylindrical structures operating in the microwave range of frequencies. Several upgrades, presently underway, will enable the facility to explore higher accelerating gradients, and also be able to generate longer RF pulses of higher intensity. The major items included in the upgrade are: (a) a new RF gun with a higher quantum efficiency photocathode will replace the RF gun that has been used to generate the drive bunches; (b) the existing RF gun will be used to generate a witness beam to probe the wakefields; (c) three new L-band RF power stations, each providing 25 MW, will be added to the facility; (d) five linac structures will be added to the drive beamline, bringing the beam energy up from 15 MeV to 75 MeV. The upgraded drive beam will consist of bunch trains of up to 32 bunches spaced by 0.77 ns with up to 100 nC per bunch. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level.

WEPZ016

Generation and Characterization of Electron Bunches with Ramped Current Profiles at the FLASH Facility

laser, wakefield, linac, free-electron-laser

2805

P. Piot
Fermilab, Batavia, USA
C. Behrens, C. Gerth, M. Vogt
DESY, Hamburg, Germany
F. Lemery, D. Mihalcea
Northern Illinois University, DeKalb, Illinois, USA

Funding: This work was supported the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10^-1-0051, to Northern Illinois University and the German's Bundesministerium f\"ur Bildung und Forschung
We report on the successful generation of electron bunches with current profiles that have a quasi-linear dependency on the longitudinal coordinate. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a linac operating at two frequencies (1.3 and 3.9 GHz) and a bunch compressor. Data taken for various accelerator settings demonstrate the versatility of the method. The produced bunches have parameters well matched to drive high-gradient accelerating field with enhanced transformer ratio in beam-driven accelerators based on sub-mm-sizes dielectric or plasma structures.

WEPZ017

ESTB: A New Beam Test Facility at SLAC

kicker, hadron, linac, emittance

2808

M.T.F. Pivi, H. Fieguth, C. Hast, R.H. Iverson, J. Jaros, R.K. Jobe, L. Keller, T.V.M. Maruyama, D.R. Walz, M. Woods
SLAC, Menlo Park, California, USA

Funding: Work supported by the Director, Office of Science, High Energy Physics, U.S. DOE under Contract No. DE-AC02-76SF00515.
End Station A Test Beam (ESTB) is a beam line at SLAC using a small fraction of the bunches of the 13.6 GeV electron beam from the Linac Coherent Light Source (LCLS), restoring test beam capabilities in the large End Station A (ESA) experimental hall. ESTB will provide one of a kind test beam essential for developing accelerator instrumentation and accelerator R&D, performing particle and particle astrophysics detector research, linear collider machine and detector interface (MDI) R&D studies, development of radiation-hard detectors, and material damage studies with several distinctive features. In the past, 18 institutions participated in the ESA program at SLAC. In stage I, 4 new kicker magnets will be added to divert 5 Hz of the LCLS beam to ESA. A new beam dump is installed and a new Personnel Protection System (PPS) is built in ESA. In stage II, we plan to install a secondary hadron target, able to produce pions up to about 12 GeV/c at 1 particle/pulse. We report about the ESTB commissioning, status and plan for tests.

WEPZ023

Results from Plasma Wakefield Acceleration Experiments at FACET

plasma, wakefield, acceleration, diagnostics

2814

S.Z. Li, C.I. Clarke, R.J. England, J.T. Frederico, S.J. Gessner, M.J. Hogan, R.K. Jobe, M.D. Litos, D.R. Walz
SLAC, Menlo Park, California, USA
E. Adli
University of Oslo, Oslo, Norway
W. An, C.E. Clayton, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori, S. Tochitsky
UCLA, Los Angeles, California, USA
P. Muggli
USC, Los Angeles, California, USA

Funding: Work supported by the U.S. Department of Energy under contract number DE- AC02-76SF00515.
We report initial results of the Plasma Wakefield Acceleration (PWFA) Experiments performed at FACET - Facility for Advanced aCcelertor Experimental Tests at SLAC National Accelerator Laboratory. At FACET a 23 GeV electron beam with 1.8x10¹0 electrons is compressed to 20 microns longitudinally and focused down to 10 microns x 10 microns transverse spot size for user driven experiments. Construction of the FACET facility completed in May 2011 with a first run of user assisted commissioning throughout the summer. The first PWFA experiments will use single electron bunches combined with a high density lithium plasma to produce accelerating gradients >10GeV/m benchmarking the FACET beam and the newly installed experimental hardware. Future plans for further study of plasma wakefield acceleration will be reviewed.

WEPZ024

Some Considerations in Realizing a TeV Linear Collider Based on the PDPWA Scheme

proton, plasma, wakefield, collider

2817

G.X. Xia, A. Caldwell
MPI-P, München, Germany
P. Muggli
MPI, Muenchen, Germany

Proton-driven plasma wakefield acceleration (PDPWA) has recently been proposed as an approach to bring the electron beam to the energy frontier in a single passage of acceleration. Particle-in-Cell (PIC) simulation shows that a TeV proton bunch, with a bunch intensity of 10¹¹, and a bunch length as short as 10⁰ microns can resonantly excite a large amplitude plasma wakefield and accelerate an externally injected electron bunch to 600 GeV in a single stage of 500 m long plasma. This novel PDPWA scheme may open a new path for designing a TeV linear lepton collider by using the currently available proton drivers. In this paper, we investigate some key issues, e.g. bunch length, centre-of-mass (CoM) energy, luminosity and dephasing in realizing a TeV linear collider based on the PDPWA scheme.

WEPZ025

Study of Self-injection of an Electron Beam in a Laser-driven Plasma Cavity

plasma, laser, simulation, injection

2820

S. Krishnagopal, S.A. Samant, D. Sarkar
BARC, Mumbai, India
P. Jha
Lucknow University, Lucknow, India
A.K. Upadhyay
CBS, Mumbai, India

Over the last few years, remarkable advances in laser wakefield acceleration of electrons have been achieved, including quasi-monoenergetic beams and GeV energy in a few centimeters. However, it is necessary to achieve good beam quality (large current, low energy-spread and low emittance) for applications such as free-electron lasers. We study self-injection in two regimes of the laser-plasma interaction: the moderate intensity, self-guiding regime, and the low intensity, near-injection-threshold regime, both in a homogeneous plasma that completely fills the simulation volume. We find good beam quality with injection of on-axis electrons, especially at lower intensity. We also study the case when the laser has to travel through vacuum before entering the plasma. We find that injection here is completely different, from off-axis electrons, and the beam quality is poorer.

WEPZ027

Stabilization of the LWFA and its Application to the Single-shot K-edge Densitometry

scattering, laser, emittance, wakefield

2823

K. Koyama, H. Madokoro, Y. Matsumura
University of Tokyo, Tokyo, Japan
R. Kuroda, K. Yamada
AIST, Tsukuba, Ibaraki, Japan
H. Masuda, M. Uesaka
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
S. Masuda
Osaka University, Suita, Osaka, Japan

Funding: This work was supported in part by Global COE Program “Nuclear Education and Research Initiative,” MEXT, Japan
Injection of electrons into a laser wakefield accelerator (LWFA) via a wavebreaking process was investigated in order to obtain stable output of electron bunches. A density down ramp for occurring the wavebreaking was formed by an oblique shockwave, which was excited by setting a little flow-deflector on an edge of the supersonic nozzle of high-Mach number (M=5). Parameters of the jet were examined by using PIC code and evaluated by using an interferometer, the density was 10¹⁹cm^-3, density ratio was 2, and the characteristic length was 70 microns. Injection experiments using 7-TW laser pulses suggested that electrons were injected in the density ramp. Since the all-optical Compton X-ray is attractive source for an accurate densitometry, a preliminary experiment of a single-shot K-edge densitometry was performed by using X-ray pulses generated by the laser-Compton scattering (LCS) device based on a compact S-band 40 MeV linac at AIST. The single-shot K-edge densitometry was also applicable to evaluate the transverse emittance of electron bunches.

WEPZ028

Status of Plasma Electron Hose Instability Studies in FACET

plasma, simulation, ion, emittance

2826

E. Adli
University of Oslo, Oslo, Norway
W. An, W.B. Mori
UCLA, Los Angeles, California, USA
R.J. England, J.T. Frederico, M.J. Hogan, S.Z. Li, M.D. Litos, Y. Nosochkov
SLAC, Menlo Park, California, USA

Funding: This work is supported by the Research Council of Norway, the Fulbright Visiting Scholar Program and US DOE contract DE-AC02-76SF00515.
In the FACET plasma-wakefield acceleration experiments a dense 23 GeV electron beam will interact with lithium and cesium plasmas, leading to plasma ion-channel formation. The interaction between the electron beam and the plasma sheath-electrons may lead to a fast growing electron hose instability. By using optics dispersion knobs to induce a controlled z-x tilt along the beam entering the plasma, we investigate the transverse behavior of the beam in the plasma as function of the tilt. We seek to quantify limits on the instability in order to further explore potential limitations on future plasma wakefield accelerators due to the electron hose instability.

WEPZ030

Study on a Gas-filled Capillary Waveguide for Laser Wakefield Acceleration

simulation, laser, acceleration, plasma

2829

M.S. Kim, D. Jang, D. Jang, H. Suk
APRI-GIST, Gwangju, Republic of Korea

In gas-filled capillary waveguide for lase wakefield accelerators the gas flows through the two gas feed lines used to sustain constant pressure. Compared to the supersonic gas-jet system operated under high pressure, the gas at low pressure (<1atm) is injected inside capillary waveguide, so that this waveguide has experimental limit to the measurement of the neutral density. In order to investigate the gas pressure in capillary system we used computational fluid dynamics (CFD) simulation. In this paper, we presented the gas pressure changed by a variety of parameters, such as length and sizes of gas feed lines, and the method to decrease the turbulence effect at the ends of capillary.

WEPZ031

Accelerator Studies on a Possible Experiment on Proton-driven Plasma Wakefields at CERN

plasma, proton, laser, acceleration

2832

R.W. Assmann, I. Efthymiopoulos, S.D. Fartoukh, G. Geschonke, B. Goddard, C. Heßler, S. Hillenbrand, M. Meddahi, S. Roesler, F. Zimmermann
CERN, Geneva, Switzerland
A. Caldwell, G.X. Xia
MPI-P, München, Germany
P. Muggli
MPI, Muenchen, Germany

There has been a proposal by Caldwell et al to use proton beams as drivers for high energy linear colliders. An experimental test with CERN's proton beams is being studied. Such a test requires a transfer line for transporting the beam to the experiment, a focusing section for beam delivery into the plasma, the plasma cell and a downstream beam section for measuring the effects from the plasma and safe disposal of the beam. The work done at CERN towards the conceptual layout and design of such a test area is presented. A possible development of such a test area into a CERN test facility for high-gradient acceleration experiments is discussed.

WEPZ032

Energy Spectrometer Studies for Proton-driven Plasma Acceleration

plasma, proton, simulation, acceleration

2835

S. Hillenbrand, R.W. Assmann, F. Zimmermann
CERN, Geneva, Switzerland
S. Hillenbrand, A.-S. Müller
KIT, Karlsruhe, Germany
T. Tückmantel
HHUD, Dusseldorf, Germany

Plasma-based acceleration methods have seen important progress over the last years. Recently, it has been proposed to experimentally study plasma acceleration driven by proton beams, in addition to the established research directions of electron and laser driven plasmas. Here, we present the planned experiment with a focus on the energy spectrometer studies carried out.

WEPZ034

Double Resosnant Plasma Wakefields

plasma, laser, simulation, wakefield

2838

B.D. O'Shea, A. Fukasawa, B. Hidding, J.B. Rosenzweig, S. Tochitsky
UCLA, Los Angeles, California, USA
D.L. Bruhwiler
Tech-X, Boulder, Colorado, USA

Present work in Laser Plasma Accelerators focuses on a single laser pulse driving a non-linear wake in a plasma. Such single pulse regimes require ever increasing laser power in order to excite ever increasing wake amplitudes. Such high intensity pulses can be limited by instabilities as well engineering restrictions and experimental constraints on optics. Alternatively we present a look at resonantly driving plasmas using a laser pulse train. In particular we compare analytic, numerical and VORPAL simulation results to characterize a proposed experiment to measure the wake resonantly driven by four Gaussian laser pulses. The current progress depicts the interaction of 4 CO2 laser pulses, λlaser = 10.6μm, of 3 ps full width at half max- imum (FWHM) length separated peak-to-peak by 18 ps, each of normalized vector potential a0 ≃ 0.7. Results con- firm previous discourse (*,**) and show, for a given laser pro- file, an accelerating field on the order of 900 MV/m, for a plasma satisfying the resonant condition, ωp=π/t_fwhm.
* Umstadter, D., et al, Phys. Rev. Lett. 72, 1224
** Umstadter, D., et al, Phys. Rev. E 51, 3484

WEPZ036

A Multi-Parameter Optimization of Plasma Density for an Advanced Linear Collider

plasma, ion, focusing, emittance

2841

P. Muggli
USC, Los Angeles, California, USA
R.W. Assmann
CERN, Geneva, Switzerland
S. Hillenbrand
KIT, Karlsruhe, Germany
P. Muggli
MPI, Muenchen, Germany

Funding: Work supported by US DoE
Recent plasma wakefield accelerator (PWFA) experiments showed that an accelerating gradient as high as 50GV/m can be driven and sustained over a meter-long plasma*. Based on this result, a strawman design for a future, multi-stage, PWFA-based electron/positron collider with an energy gain of ~25GeV/stage has been generated**. However, the choice of plasma density remains open. On one hand, high density means large accelerating gradients and possibly a shorter collider. On the other it means that the accelerating structure dimensions become very small, on the order of the plasma wavelength (<100 microns in each dimension?). Operating at high gradient and with such small structure imposes very strong constraints on the particle bunches: small dimensions and spacing, large current or limited charge, etc. These constraints result in challenges in producing bunches (compression, shaping for optimum loading, etc.) and could limit the achievable collider luminosity (beam-beam effects, etc.). We explore the global implications of operating at a lower accelerating gradient with the goal of relaxing the beam and plasma parameters while meeting the requirements of the collider.
* P. Muggli and M.J. Hogan, Comptes Rendus Physique, 10(2-3), 116 (2009).
** A. Seryi, M.J. Hogan, T. Raubenheimer, private communication.

THOBA01

Electron Cloud Observations in LHC

vacuum, injection, emittance, simulation

2862

G. Rumolo, G. Arduini, V. Baglin, H. Bartosik, P. Baudrenghien, N. Biancacci, G. Bregliozzi, S.D. Claudet, R. De Maria, J. Esteban Muller, M. Favier, C. Hansen, W. Höfle, J.M. Jimenez, V. Kain, E. Koukovini, G. Lanza, K.S.B. Li, G.H.I. Maury Cuna, E. Métral, G. Papotti, T. Pieloni, F. Roncarolo, B. Salvant, E.N. Shaposhnikova, R.J. Steinhagen, L.J. Tavian, D. Valuch, W. Venturini Delsolaro, F. Zimmermann
CERN, Geneva, Switzerland
C.M. Bhat
Fermilab, Batavia, USA
U. Iriso
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
N. Mounet, C. Zannini
EPFL, Lausanne, Switzerland

Operation of LHC with bunch trains different spacings has revealed the formation of an electron cloud inside the machine. The main observations of electron cloud build-up are the pressure rise measured at the vacuum gauges in the warm regions, as well as the increase of the beam screen temperature in the cold regions due to an additional heat load. The effects of the electron cloud were also visible as a strong instability and emittance growth affecting the last bunches of longer trains, which could be improved running with higher chromaticity and/or larger transverse emittances. A summary of the 2010 and 2011 observations and measurements and a comparison with existing models will be presented. The efficiency of scrubbing and scrubbing strategies to improve the machine running performance will be also briefly discussed.

Slides THOBA01 [2.911 MB]

THOAB02

Metal Nano-particle Synthesis by using Proton Beam

proton, controls, radiation, cyclotron

2871

M.H. Jung, K. R. Kim, S.J. Ra
KAERI, Daejon, Republic of Korea

Funding: This work was conducted as a part of the Proton Engineering Frontier Project supported by the Ministry of Education Science & Technology of Korea Government.
Many scientists have studied metal nano-particles for newly known optical, electronic and chemical properties. The unique properties of nano-particles have a tendency to relate the particle size and shape. Electron beam have been used for the nano-particle synthesizing and many results were published. Study of nano-particles synthesize by using proton beam is still in the early stages however study for gold, silver, platinum and cobalt nano-particle was in progress. 100 MeV proton linear accelerator, which is by Proton Engineering Frontier Project, Korea Atomic Energy Research Institute, is scheduled to be completed by 2012. Study of nano-particle synthesize by using proton beam will become active due to the completion of 100 MeV proton accelerator and it can be mass-produced because of the large current beam. Finally, industrial applications could become possible. The mechanism of metal nano-particles synthesizing by proton beam irradiation was not completely known. In this study, we investigated the changes of size and shape for metal nano-particle depending on the condition of proton beam irradiation, and concentration of additives by TEM and UV/Vis spectrophotometer.

Slides THOAB02 [9.791 MB]

THOBB01

Evaluation of Performance, Reliability, and Risk for High Peak Power RF Sources from S-band through X-band for Advanced Accelerator Applications

klystron, high-voltage, linac, focusing

2882

M.V. Fazio, C. Adolphsen, A. Jensen, C. Pearson, D.W. Sprehn, A.E. Vlieks, F. Wang
SLAC, Menlo Park, California, USA
M.V. Fazio
LANL, Los Alamos, New Mexico, USA

Historically linear accelerator development and the choice of frequency have been driven by the availability of RF power sources. This is also true at the present time and is particularly significant as new accelerators are being conceived and planned over a wide frequency range for FEL light sources and other applications. This paper evaluates the current state of the technology for high peak power RF sources from S-band through X-band including reliability and the facility risk incurred for applications demanding high availability and decades-long operation.

Slides THOBB01 [2.326 MB]

THPPA00

Study of Beam Diagnostics with Trapped Modes in Third Harmonic Superconducting Cavities at FLASH

cavity, dipole, HOM, simulation

2891

P. Zhang
DESY, Hamburg, Germany
P. Zhang
UMAN, Manchester, United Kingdom

Contribution selected for EPS-AG Prize d). Off-axis beams passing through an accelerating cavity excite dipole modes among other higher order modes (HOMs). These modes have linear dependence on the transverse beam offset from the cavity axis. Therefore they can be used to monitor the beam position within the cavity. The fifth dipole passband of the third harmonic superconducting cavities at FLASH has modes trapped within each cavity and do not propagate through the adjacent beam pipes, while most other cavity modes do. This could enable the beam position measurement in individual cavities. This paper investigates the possibility to use the fifth dipole band for beam alignment in the third harmonic cavity module. Simulations and measurements both with and without beam-excitations are presented. Various analysis methods are used and compared. A good correlation of HOM signals to the beam position is observed.

Slides THPPA00 [2.740 MB]

THPPA02

EPS-AG Budker Prize Presentation: Retrospective of 24 years of RIBF Life

cyclotron, factory, ion, scattering

2899

Y. Yano
RIKEN Nishina Center, Wako, Japan

The speaker will look back on 24 years (from 1987 to now) devoted to the RIBF project.

Slides THPPA02 [10.303 MB]

THPC006

Experiments to Measure Electron Beam Energy using Spin Depolarization Method on SOLEIL Storage Ring

polarization, storage-ring, beam-losses, synchrotron

2915

J.F. Zhang, L. Cassinari, M. Labat, A. Nadji, L.S. Nadolski, D. Pédeau
SOLEIL, Gif-sur-Yvette, France

The electron beam energy on SOLEIL storage ring was successfully measured using spin depolarization method after several attempts over the past few years. The experimental results demonstrate that the effective polarization was 91.3%±3% and polarization time was 17±2.3 minutes as expected from the simulation using SLIM code. The beam was depolarized using an AC shaker and the depolarization was monitored using DCCT and beam loss monitors. The beam energy was measured with accuracy up to a few 10^-5.

THPC007

Laser Electron Interaction Simulation for the Femtosecond Bunch Slicing on SOLEIL Storage Ring

laser, wiggler, simulation, storage-ring

2918

J.F. Zhang, M.-E. Couprie, M. Labat, A. Loulergue, A. Nadji
SOLEIL, Gif-sur-Yvette, France

The interaction of an electron bunch and a laser in a wiggler (modulator) to generate a femtosecond slice is simulated for the slicing project on SOLEIL storage ring, using a code based on Monte-Carlo method and GENESIS. The results from these two codes are consistent with the theoretical values. The maximum modulated energy of the electron bunch and the number of electrons above a certain limit are studied for different wiggler and laser parameters. The transport of the 6D distribution of the sliced bunch from the modulator to the radiators are simulated using AT (Accelerator Toolbox) and ELEGANT, with synchrotron radiation on and taking into account the collective effects of the sliced bunch core.

THPC008

Touschek Lifetime and Momentum Acceptance Measurements for ESRF

vacuum, emittance, scattering, synchrotron

2921

B. Nash, F. Ewald, L. Farvacque, J. Jacob, E. Plouviez, J.-L. Revol, K.B. Scheidt
ESRF, Grenoble, France

The Touschek lifetime of a synchrotron results from electrons scattering off one another within the bunch and subsequently being lost. We have measured the Touschek lifetime for the major operating modes of the ESRF as a function of RF voltages. This includes multibunch and few bunch filling patterns with correspondingly different chromaticity values. Through calibration of the RF voltage and measurement of the other beam parameters such as bunch length and vertical emittance, we may understand the momentum acceptance in the regime where this is determined by non-linear dynamics effects.

THPC013

THz Studies at a Dedicated Beamline at the MLS

radiation, synchrotron, synchrotron-radiation, storage-ring

2933

R. Müller, A. Hoehl, A. Serdyukov, G. Ulm
PTB, Berlin, Germany
J. Feikes, M. Ries, G. Wüstefeld
HZB, Berlin, Germany

The Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute is operating the low-energy electron storage ring Metrology Light Source (MLS) in Berlin-Adlershof in close cooperation with the Helmholtz-Zentrum Berlin. The MLS is designed and prepared for a special machine optics mode (low-alpha operation mode) based on a sextupole and octupole correction scheme, for the production of coherent synchrotron radiation in the THz region*. At the MLS two bending magnet beamlines dedicated to the use of IR and THz synchrotron radiation are in operation: the MLS-IR beamline optimized for the NIR to FIR, and a dedicated THz beamline optimized for the FIR/THz spectral range**. Low-alpha operation optic modes for different ring energies, 250 MeV, 350 MeV, 450 MeV and 630 MeV are available. We compare the THz spectra taken in the different low-alpha modes and discuss the results.
* J. Feikes et al., Phys. Rev. ST Accel. Beams 14, 030705 (2011).
** R. Müller et al., J. Infrared Milli Terahz Waves, in press (2011), DOI: 10.10⁰⁷/s10762-011-9785-6.

THPC014

Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring

cavity, optics, focusing, radiation

2936

G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries
HZB, Berlin, Germany

A scheme is discussed, where short and long bunches can be stored simultaneously in the BESSY II storage ring. With recent developments in sc-rf cavity technology it becomes possible, to install high gradient cavities in electron storage rings. With an appropriate choice of these cavities stable fixed points with different rf-voltage gradients are available, leading to different zero current bunch lengths. For BESSY II, we discuss the simultaneously storage of bunches with rms-lengths of 2 ps and 15 ps at high beam intensities. Additionally, in a low alpha optics sub-ps and ps-bunches are possible and a double bucket optics can be set up to store the two types of beams simultaneously on different orbits. Ultra-short and long bunches can be supplied to the users, separated by slightly different orbits.

THPC015

A Dedicated THz Beamline at DELTA

laser, radiation, simulation, undulator

2939

M. Höner, M. Bakr, H. Huck, S. Khan, R. Molo, A. Nowaczyk, A. Schick, P. Ungelenk, M. Zeinalzadeh
DELTA, Dortmund, Germany

Funding: Work supported by DFG, BMBF, and by the Federal State NRW
As a consequence of the new radiation source for ultrashort VUV pulses at DELTA, which is based on the interaction of electrons with fs laser pulses, coherent THz radiation is emitted. Simulations of the laser-electron interaction, particle dynamics and radiation spectrum, as well as the optical and mechanical design of a dedicated THz beamline are presented. First experimental results including laser-electron overlap diagnostics and characterization of the THz radiation are discussed.

THPC016

Ultrashort VUV and THz Pulse Generation at the DELTA Storage Ring

laser, undulator, radiation, klystron

2942

A. Schick, M. Bakr, H. Huck, M. Höner, S. Khan, R. Molo, A. Nowaczyk, P. Ungelenk, M. Zeinalzadeh
DELTA, Dortmund, Germany

Funding: Supported by DFG, BMBF, and the Federal State NRW
The optical klystron (two undulators, separated by a dispersive section) at DELTA, formerly operated as storage-ring FEL, is seeded with ultrashort pulses from a Ti:Sapphire laser. The thus induced energy modulation of an electron bunch in the first undulator is converted to a density modulation within the dispersive chicane. In the second undulator, the micro-bunched electrons emit ultrashort pulses coherently at harmonics of the fundamental laser wavelength. Additionally, coherent ultrashort THz pulses are generated several meters downstream of the optical klystron by the laser-induced gap in the electron bunch. First results are presented.

THPC017

Temporal and Spatial Alignment of Electron Bunches and Ultrashort Laser Pulses for the CHG Experiment at DELTA

laser, undulator, controls, synchrotron

2945

M. Zeinalzadeh, M. Bakr, H. Huck, M. Höner, S. Khan, R. Molo, A. Nowaczyk, A. Schick, P. Ungelenk
DELTA, Dortmund, Germany

Funding: Supported by DFG, BMBF, and the Federal State NRW
The generation of ultrashort VUV pulses by CHG (Coherent Harmonic Generation) requires achieving and maintaining the longitudinal and transversal overlap of femtosecond laser pulses and electron bunches. We present the techniques and the experimental setup applied at the DELTA storage ring. For the longitudinal analysis, both a streak camera and a fast photo diode are used. Transversely, two CCD cameras acquire images of laser and synchrotron light at different positions inside of the undulator. A feedback system utilizes the intensity of a THz signal generated several meters downstream of the undulator to optimize and maintain the overlap.

THPC025

Booster Design for ILSF

booster, synchrotron, storage-ring, dipole

2960

H. Ghasem
IPM, Tehran, Iran
E. Ahmadi
ILSF, Tehran, Iran
D. Einfeld
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain

A full energy 3 GeV booster synchrotron has been designed to boost electron beam to the target energy of 3 GeV for the proposed third generation synchrotron light source (ILSF) that will be constructed in Iran. The primary goal of the ILSF booster is to design a synchrotron which can deliver a small emittance (ε<30 nm-rad), while at the same time has a low cost in construction. In order to design lattice for the booster, two configurations for booster have been considered. In the first configuration, booster is designed based on locating in a separate tunnel as 3 GeV storage ring inside the ring and in the second configuration, the booster is optimized for placing inner to the ring with one shared wall as service area of ILSF storage ring. Several types of lattice with various circumferences have been explored for the booster synchrotron in each configuration and this paper presents results of linear and nonlinear optimization of the main designed lattice for booster in both configurations.

THPC028

A Proposal of Short X-ray Pulse Generation from Compressed Bunches by mm-wave iFEL in the SPring-8 Upgrade Plan

storage-ring, wiggler, injection, simulation

2969

M. Masaki, K. Fukami, C. Mitsuda, T. Watanabe
JASRI/SPring-8, Hyogo-ken, Japan

In the SPring-8 upgrade plan, short pulse options are prepared for time-resolved experiments of pico-second order with high repetition rate. The best scenario is that selected bunches have equilibrium bunch length of 1 ps or less. A mm-wave storage-ring iFEL may be one possible solution for it. If resonant wavelength of the FEL is a few millimeters, which is about ten times longer than typical short bunch length of 0.3 mm corresponding to 1 ps, almost all electrons of a bunch can be confined in one valley of ponderomotive potentials formed by the FEL mechanism. The system consists of a helical wiggler with period length of several meters and a mm-wave resonator. Numerical simulations with coherent synchrotron radiation effect at bunch charge of 479 pC show that an ultra-short injection bunch is trapped in a mm-wave “bucket” and kept shorter than 1 ps (r.m.s.) even after twice the longitudinal damping time from the injection. The ultra-short bunches need to be injected from the XFEL linac. XFEL-to-Storage Ring beam transport line is designed to suppress dispersions which cause bunch lengthening. Tracking calculations show promising results for bunch qualities at the transport line.

THPC032

Current Status of SPring-8 Upgrade Plan

lattice, emittance, brilliance, injection

2981

T. Watanabe, T. Asaka, H. Dewa, H. Ego, T. Fujita, K. Fukami, M. Masaki, C. Mitsuda, A. Mochihashi, T. Nakamura, H. Ohkuma, Y. Okayasu, Y. Shimosaki, K. Soutome, M. Takao
JASRI/SPring-8, Hyogo-ken, Japan
T. Tanaka
RIKEN Spring-8 Harima, Hyogo, Japan

The SPring-8 upgrade plan has been discussed. The main goal is to replace the storage ring in the existing tunnel so that the resulting emittance will get as close to the diffraction limit in hard x-ray region as possible. For 10 keV photons, for instance, the diffraction limit corresponds to the emittance of as small as 10 pm.rad. For the challenging goal, the new ring features a multi-bend lattice with damping wigglers, which presumably enables us to reduce an emittance by two orders of magnitudes or more compared with the current double-bend lattice without damping wigglers. Up to now, a six-bend lattice has been mainly studied, which is supposed to generate a natural emittance of 60–70 pm.rad for 6 GeV. In addition, damping wigglers and coupling control should assist to reduce the emittance even more for approaching the ultimate goal. The major modification requires not only an advanced lattice design via manipulation of non-linear beam dynamics but also extensive technological developments in almost every component such as magnets, monitors, and RF systems. The overall review of the upgrade plan, including some detailed discussions on the critical issues, will be presented.

THPC037

Accelerators of the Central Japan Synchrotron Radiation Facility Project (II)

storage-ring, synchrotron, booster, linac

2987

N. Yamamoto, M. Hosaka, A. Mano, H. Morimoto, K. Takami, Y. Takashima
Nagoya University, Nagoya, Japan
Y. Hori
KEK, Ibaraki, Japan
M. Katoh
UVSOR, Okazaki, Japan
S. Koda
SAGA, Tosu, Japan
S. Sasaki
JASRI/SPring-8, Hyogo-ken, Japan

Central Japan Synchrotron Radiation (SR) Facility Project is making progress for the service from FY2012. The construction of SR building is almost completed in the Aichi area of Japan, and the installs of accelerators will start in a few week. The key equipments of our accelerators are an 1.2 GeV compact electron storage ring that is able to supply hard X-rays and a full energy injector for top-up operation. The beam current and natural emittance of the storage ring are 300 mA and 53 nmrad. The circumference is 72 m. The magnetic lattice consists of four triple bend cells and four straight sections. The bending magnets at the centers of the cells are 5 T superconducting magnets and the critical energy of the SR is 4.8 keV. The injector consists of a 50 MeV linac and a booster synchrotron with the circumference of 48 m. To save construction expenses, the injector is built at inside of the storage ring. More than ten hard X-ray beam-line can be constructed. One variable polarization undulator will be installed in the first phase. The top-up operation will be introduced as early as possible.

THPC040

Expected Performance Characteristic of Accelerator-based THz Source at Tohoku University

radiation, undulator, focusing, gun

2990

H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, School of Science, Sendai, Japan
N.Y. Huang
NTHU, Hsinchu, Taiwan

Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
Sources of coherent synchrotron radiation at THz wavelength region have been constructed at Tohoku University. Bunch train of extremely shorter electron pulse less than 100 fs will be provided by an injector linac employing thermionic rf gun, where the bunch compression will be performed by means of velocity bunching in an accelerator structure. Radiation source under development are a Halbach type planar undulator and an accumulator isochronous ring. The undulator employs large gap and long period length configuration, so that the resonant frequency of 1 THz is achieved when a lower beam energy of ~ 20 MeV. Since spectrum of coherent synchrotron radiation (CSR) is strongly depending on longitudinal bunch form factor, we have calculated CSR spectra for various conditions of the beam to evaluate the performance of the THz source. Numerical simulation with multi-particle system has been carried out to understand the radiation power and angular distribution as well. The beam transport in the undulator is crucial for quality of the radiation because the beam energy is very much low relative to strong focusing power. Characteristics of THz CSR from the undulator will be discussed.

THPC041

Injector System of Test Accelerator as Coherent Terahertz Source

gun, cavity, cathode, radiation

2993

S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, School of Science, Sendai, Japan
N.Y. Huang
NTHU, Hsinchu, Taiwan
F. Miyahara
KEK, Ibaraki, Japan

Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
A test accelerator as a coherent terahertz source (t-ACTS) project has been under development at Tohoku University, in which a generation of intense coherent terahertz (THz) radiation from sub-picosecond electron bunch will be demonstrated. We will supply a wide-band coherent radiation from bending magnets in an isochronous ring and a narrow-band coherent THz radiation using an undulator in a linac. Stable generation of very short electron bunch is one of the key issues in the t-ACTS project. The injector system is consists of a thermionic RF gun with two independent cavity cells, an alpha magnet and an accelerating structure. A velocity bunching scheme is employed to produce the very short electron bunch. Components of the t-ACTS injector except the accelerating structure have already been installed and we have started a high power RF processing of the gun cavities. The characteristics of electron bunch extracted from the RF gun are measured by varying phase and amplitude of input RF fields for the gun cavities. The status of t-ACTS project will be presented in the conference.

THPC053

Shanghai Soft X-Ray Free Electron Laser Test Facility

laser, radiation, linac, FEL

3011

Z.T. Zhao
SINAP, Shanghai, People's Republic of China

As a critical development step towards constructing a hard X-ray FEL in China, a soft X-ray FEL test facility (SXFEL) was proposed and will be constructed at the SSRF campus by a joint team of Institute of Tsinghua University and Shanghai Institute of Applied Physics. This test facility, based on an 840MeV electron linear accelerator, aims at generating 9nm FEL radiation with two-stage cascaded HGHG scheme. The project proposal was approved in February 2011 by central government, and the constrction is expected to start in early 2012. This paper describes the preliminary design of this soft X-ray test facility and the R&D progress of the key FEL technologies in the SDUV-FEL test bench.

THPC068

CSR and THz Emission Measurements at the Diamond Light Source

radiation, bunching, dipole, vacuum

3050

R. Bartolini, G. Cinque, G. Rehm, C.A. Thomas
Diamond, Oxfordshire, United Kingdom
I.P.S. Martin
JAI, Oxford, United Kingdom

After the successful implementation of the low alpha optics at Diamond we have started a characterisation of coherent THz emission with the aim of classifying the rich phenomenology of stable and bursting emission and to devise the best operational mode for potential THz users. In conjunction with the Diamond IR beamline B22, THz spectral data were acquired simultaneously with Schottky diode signals in the mm-wave region of the spectrum. We also report the results of comparison with numerical simulations made with the aim of reproducing the measured THz emission spectra and gaining further understanding on the mechanisms of the instability.

THPC079

Echo-enabled Harmonic Generation at DELTA

undulator, laser, bunching, storage-ring

3074

R. Molo, M. Bakr, H. Huck, M. Höner, S. Khan, A. Nowaczyk, A. Schick, P. Ungelenk, M. Zeinalzadeh
DELTA, Dortmund, Germany

Funding: Supported by DFG, BMBF, and the Federal State NRW
We present conceptual studies of the realization of the echo-enabled harmonic generation (EEHG) technique proposed by G. Stupakov* as an upgrade of the present coherent harmonic generation (CHG) project at the DELTA storage ring**. EEHG allows to reach shorter wavelengths compared to the CHG scheme. In addition to the optical klystron used for CHG, a third undulator is needed for a second energy modulation of the electron bunch, followed by an additional strong dispersive section. Installing these insertion devices requires a new long straight section in the storage ring and a new lattice configuration.
* G. Stupakov Phys. Rev. Lett. 10², 074801 (2009)
** A. Schick et al., this conference

THPC082

Properties of the Radiation from the European X-ray Free Electron Laser

FEL, undulator, radiation, emittance

3083

E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

Recent success of the Linac Coherent Light Source (LCLS) demonstrated feasibility for reliable production, compression, and acceleration of electron beams with emittances significantly smaller than original baseline parameters. The same scenario can be applied to the European XFEL as well. Experimental results from the Photo Injector Test Facility in Zeuthen (PITZ) demonstrated the possibility to generate electron beams with small charge and emittance. Computer modeling of the beam formation system also indicate on the possibility to preserve electron beam quality during acceleration and compression. Recently these trends have been analyzed, and baseline parameters of the European XFEL have been revised. Parameter space has been significantly extended in terms of the bunch charge. As a result, different modes of FEL operation become possible with essentially different properties of the radiation. In this paper we present an overview of radiation properties of SASE FEL radiators driven by electron beam with new baseline parameters.

THPC083

Analysis of Parameter Space of a Kilowatt-scale Free Electron Laser for Extreme Ultraviolet Lithography Driven by L-band Superconducting Linear Accelerator Operating in a Burst Mode

radiation, FEL, undulator, laser

3086

E. Schneidmiller, V. Vogel, H. Weise, M.V. Yurkov
DESY, Hamburg, Germany

The driving engine of the Free Electron Laser in Hamburg (FLASH) is an L-band superconducting accelerator. It is designed to operate in a burst mode with 800 microsecond pulse duration at a repetition rate of 10 Hz. The maximum accelerated beam current during the macropulse is 10 mA. In this paper we analyze the parameter space for optimum operation of the FEL at the wavelength of 13.5 nm and 6.7 nm. Our analysis shows that the FLASH technology holds great potential for increasing the average power of the linear accelerator and an increase of the conversion efficiency of the electron kinetic energy to the light. Thus, it will be possible to construct a FLASH like free electron laser with an average power up to 3 kW. Such a source meets the requirements of the light source for the next generation lithography.

THPC084

Optical Afterburner for a SASE FEL: First Results from FLASH

radiation, FEL, undulator, resonance

3089

M. Foerst
CFEL, Hamburg, Germany
M. Gensch
HZDR, Dresden, Germany
R. Riedel, E. Schneidmiller, N. Stojanovic, F. Tavella, M.V. Yurkov
DESY, Hamburg, Germany

Radiation Pulse from a Self-Amplified Spontaneous Emission Free Electron Laser (SASE FEL) consists out of spikes (wavepackets). Energy loss in the electron beam (averaged over radiation wavelength) also exhibits spiky behaviour on a typical scale of coherence length, and follows the radiation pulse envelope. These modulations of the electron beam energy are converted into large density (current) modulations on the same temporal scale with the help of a dispersion section, installed behind the x-ray undulator. Powerful optical radiation is then generated with the help of a dedicated radiator (afterburner). Envelope of the optical afterburner pulse is closely resembles the envelope of the x-ray pulse. We have recently demonstrated this principle at the Free Electron Laser in Hamburg (FLASH). We use THz undulator that is installed after the main X-ray as both dispersive element and radiator simultaneously. We characterize properties of the optical pulse using standard laser diagnostics techniques (i.e. FROG). Main result comes from the pulse duration measurement that we use to derive envelope of the x-ray radiation pulse duration which is in sub-100 fs range.

THPC086

Status Report on FERMI@Elettra Project

FEL, photon, linac, undulator

3095

F. Parmigiani, M. Svandrlik, D. Zangrando
ELETTRA, Basovizza, Italy

Funding: This work was supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3
FERMI@Elettra, a single-pass FEL user-facility covering the wavelength range from 100 nm (12 eV) to 3 nm (413 eV) located next to the third-generation synchrotron radiation facility Elettra in Trieste, Italy is actually under completion and will start user operation next year. The first seeded lasing was observed in December 2010 and the first experiments have started this year. In this paper an overview of the present status of machine and beamlines systems will be given as well as a status about operation and future upgrade.

THPC087

Saturation Effect on VUV Coherent Harmonic Generation at UVSOR-II

laser, simulation, FEL, bunching

3098

T. Tanikawa, M. Adachi, M. Katoh, J. Yamazaki, H. Zen
UVSOR, Okazaki, Japan
M. Hosaka, Y. Taira, N. Yamamoto
Nagoya University, Nagoya, Japan

Light source technologies based on laser seeding are under development at the UVSOR-II electron storage ring. In the past experiments, we have succeeded in generating coherent harmonics (CHs) in deep ultraviolet (UV) and vacuum UV (VUV) region and also in generating CH with variable polarizations in deep UV*. In previous conference, we reported an introduction of new-constructed spectrometer for VUV and results of spectra measurement, undulator gap dependence, and injection laser power dependence on VUV CHs**. This time we have successfully observed saturation on CHs intensities　and have found some interesting phenomena in different harmonic orders. In this conference, we will discuss the results of some systematic measurements and those analytical and particle tracking simulations***.
*M. Labat et al., Phys. Rev. Lett. 10¹ (2008) 164803.
**T. Tanikawa et al., Proc. IPAC'10, TUPE029, p. 2206 (2010).
***T. Tanikawa et al., Appl. Phys. Express 3 (2010) 122702.

THPC088

Performance of RF System for XFEL/SPring-8 Injector

cavity, gun, emittance, klystron

3101

T. Asaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Asaka, H. Ego, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi
JASRI/SPring-8, Hyogo-ken, Japan
T. Inagaki
RIKEN/SPring-8, Hyogo, Japan
Y. Otake, T. Shintake, K. Togawa
RIKEN Spring-8 Harima, Hyogo, Japan

In the XFEL/SPring-8 accelerator, the RF processing of an injector for the 8-GeV accelerator were carried out during two months after the installation of all the main components of the accelerator was completed in January 2011. To realize stable bunch compression process without the emittance growth, the injector adopts the combination of an extremely low emittance thermionic gun and multi-stage RF cavities for velocity bunching. In addition, in order to reduce the emittance growth occurring at the transition from the velocity bunching to acceleration, the newly developed L-band APS type accelerating structures and a waveguide system were introduced in the injector. Since an intensity of beam current is affected by the slight variations of RF power and phase of these RF equipment, we have carried out thorough countermeasures to complete highly-stabilized RF systems. Consequently, the stability of RF power and phase in rated operating condition of each RF cavity achieved 20 ppm (std.) and 0.06˚ (std.), respectively. In this paper, we describe the stability performances and RF processing of these RF systems in the injector.

THPC089

Study of a Modified Quasi-periodic Undulator

undulator, radiation, photon, insertion

3104

A.L. Wu, Q.K. Jia
USTC/NSRL, Hefei, Anhui, People's Republic of China

To suppress high-order harmonic radiation effectively while maintain comparatively higher fundamental radiation intensity, a modified quasi-periodic undulator (QPU) which the magnet blocks have different size is studied in this paper. Then the paper also compares the radiation spectrum of various structural schemes. It is shown that the higher harmonic radiation of this new scheme will be suppressed more effectively than the conventional QPU.

THPC095

Commissioning Status of the SwissFEL Injector Test Facility

emittance, laser, solenoid, gun

3110

T. Schietinger, M. Aiba, S. Bettoni, B. Beutner, A. Falone, R. Ganter, R. Ischebeck, F. Le Pimpec, N. Milas, G.L. Orlandi, M. Pedrozzi, E. Prat, S. Reiche, C. Vicario
PSI, Villigen, Switzerland

The SwissFEL injector test facility at the Paul Scherrer Institute has been in operation since August 2010. Its primary goal is the demonstration of a high-brightness electron beam as it will be required to drive the SwissFEL main linac. The injector further serves as a platform for the development and validation of accelerator components needed for the SwissFEL project. We give an overview of recent commissioning activities at about 130 MeV beam energy, with particular emphasis on results from optics matching studies and emittance measurements, the latter obtained with different optics-based methods. A five-cell transverse-deflecting cavity allows studies of the longitudinal bunch charge distribution and slice emittance. Bunch length measurements will become the focus of interest after the installation of a magnetic compression chicane, currently scheduled for the summer of 2011.

THPC096

Soft X-ray Free-electron Laser with a 10-time Reduced Size

undulator, FEL, bunching, laser

3113

Y.-C. Huang, F.H. Chao, C.H. Chen, K.Y. Huang
NTHU, Hsinchu, Taiwan
P.J. Chou
NSRRC, Hsinchu, Taiwan

Funding: This work is supported by National Science Council under Contract NSC 99-2112-M-007 -013 -MY3.
We present a 30-m long soft x-ray FEL consisting of a 5-MeV photoinjector, a 150 MeV linac, a magnetic chicane compressor, and a 3-m long undulator. We employ both the 3rd and the 4th harmoincs of a Nd laser at 355 and 266 nm, respectively, to illuminate the cathode of the photoinjector. Owing to the beating of the two lasers, the emitted electron beam is modulated at 282 THz. The electrons are further accelerated to 150 MeV and, after acceleration, compressed by 33 times in a magnetic chicane. The temporal compression of the electron macropulse increases the electron bunching frequency to 9.3 PHz, corresponding to a soft x-ray wavelength of 32.2 nm. We adopt a solenoid-derived staggered array undulator* with a 3-m length, 5 mm undulator period, and 1.2 mm gap. With a solenoid field of 10 kG, we estimate an undulator parameter of 0.4 and a corresponding radiation wavelength of 32.2 nm for a 150 MeV driving beam. With 3.3-kA peak current, 0.03% energy spread, 2 mm-mrad emittance, and 80-micron beam radius at the undulator entrance, the GENESIS code predicts 0.2 GW radiation power from the 3-m long undulator for an initial bunching factor of merely 10 ppm.
* Y.C. Huang, H.C. Wang, R.H. Pantell, and J. Feinstein, "A staggered-array wiggler for far infrared, free-electron laser operation," IEEE J. Quantum Electronics 30 (1994) 1289.

THPC097

Transverse Alignment Tolerances for the European XFEL Laser Heater

laser, FEL, undulator, emittance

3116

V.A. Goryashko
NASU/IRE, Kharkov, Ukraine
M. Dohlus
DESY, Hamburg, Germany
M. Hamberg, V.G. Ziemann
Uppsala University, Uppsala, Sweden

Funding: Supported by the KTH-SU-UU FEL Center.
We study the impact of misalignments between a laser beam and an electron bunch on the energy distribution function of the electron bunch in the laser heater. Transverse position and angular misalignment as well as different spot size of the laser and electron beam are considered. We find that the transverse misalignment makes the energy distribution function narrower compared to the case of ideal adjustment and a distinct peak in the distribution around the initial mean value of the energy appears. We demonstrate that despite these misalignments a uniform heating in terms of the energy spread can be achieved by appropriately adapting the transverse size and power of the laser beam such that the energy distribution function of the electron bunch at the end of the laser heater can be made similar to a Gaussian, thus providing more effective Landau damping against the micro-bunching instability. The laser power mainly determines the local energy spread while the laser spot size governs the shape of the energy distribution function. The transverse oscillations of electrons induced by the magnetic field in the laser heater are found to be non-essential for typical operation parameters.

THPC101

Fitting Formulas for Space-charge Dominated Free-electron Lasers

FEL, space-charge, undulator, simulation

3122

G. Marcus, E. Hemsing, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

A simple power-fit formula for calculating the gain length of the fundamental Gaussian mode of a free-electron laser having strong space-charge effects in the 3D regime has been obtained. This tool allows for quick evaluation of the free-electron laser performance in the presence of diffraction, uncorrelated energy spread, and longitudinal space-charge effects. Here, we use it to evaluate the performance of high-gain FEL amplifiers considered candidates as high average power light sources. Results are compared with detailed numerical particle simulations using the free-electron laser code Genesis.

THPC102

Production of Coherent Optical \vCerenkov Radiation in Silica Aerogel

radiation, scattering, photon, emittance

3125

F.H. O'Shea, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

As a demonstration of the apposite properties of silica aerogel as an electron beam diagnostic we intend to use it to produce coherent optical Cˇ erenkov radation (COCR). In this paper we propose an experiment and provide details of the challenges to be overcome in producing COCR.

THPC103

Beam Dynamics Study of X-band Linac Driven X-ray FELs

linac, simulation, FEL, optics

3128

Y. Sun, C. Adolphsen, C. Limborg-Deprey, T.O. Raubenheimer, J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by the DOE under Contract DE-AC02-76SF00515
Several linac driven X-ray Free Electron Lasers (XFELs) are being developed to provide high brightness photon beams with very short, tunable wavelengths. In this paper, three XFEL configurations are proposed that achieve LCLS-like performance using X-band linac drivers. These linacs are more versatile, efficient and compact than ones using S-band or C-band rf technology. For each of the designs, the overall accelerator layout and the shaping of the bunch longitudinal phase space are described briefly.

THPC104

Optimization for Single-Spike X-Ray Fels at LCLS with a Low Charge Beam

undulator, laser, FEL, simulation

3131

L. Wang, Y.T. Ding, Z. Huang
SLAC, Menlo Park, California, USA

The recently commissioned Linac Coherent Light Source is an x-ray free-electron laser at the SLAC National Accelerator Laboratory, which is now operating at x-ray wavelengths of 20-1.2 Angstrom with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources. At the low charge operation mode (20 pC), the x-ray pulse length can be <10 fs. In this paper we report our numerical optimization and simulations to produce even shorter x-ray pulses by optimizing the machine and undulator setup. In the soft x-ray regime, with the help of slotted-foil or undulator taper, a single spike x-ray pulse is achievable with peak FEL power of 30 GW.

THPC106

Commissioning Status of the Fritz Haber Institute THz FEL

FEL, undulator, linac, gun

3137

A.M.M. Todd, H. Bluem, V. Christina, M.D. Cole, J. Ditta, D. Dowell, K. Jordan, R. Lange, J.H. Park, J. Rathke, T. Schultheiss, L.M. Young
AES, Princeton, New Jersey, USA
W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, W. Schöllkopf, G. von Helden
FHI, Berlin, Germany
S.C. Gottschalk
STI, Washington, USA

The THz Free-Electron Laser (FEL) at the Fritz Haber Institute (FHI) of the Max Planck Society in Berlin is designed to deliver radiation from 3 to 300 microns using a single-plane-focusing mid-IR undulator and a two-plane-focusing far-IR undulator that acts as a waveguide for the optical mode. A key aspect of the accelerator performance is the low longitudinal emittance, < 50 keV-psec, that is specified to be delivered at 200 pC bunch charge and 50 MeV from a gridded thermionic electron source. We utilize twin accelerating structures separated by a chicane to deliver the required performance over the < 20 - 50 MeV energy range. The first structure operates at near fixed field while the second structure controls the output energy, which, under some conditions, requires running in a decelerating mode. "First Light" is targeted for the centennial of the sponsor in October 2011 and we will describe progress in the commissioning of this device to achieve this goal. Specifically, the measured performance of the accelerated electron beam will be compared to design simulations and the observed matching of the beam to the mid-IR wiggler will be described.

THPC113

Slice Emittance Measurements for Different Bunch Charges at PITZ

emittance, laser, solenoid, booster

3149

Ye. Ivanisenko, H.-J. Grabosch, M. Gross, L. Hakobyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, D. Richter, S. Rimjaem, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
I.I. Isaev
MEPhI, Moscow, Russia
M.A. Khojoyan
YerPhI, Yerevan, Armenia
I.H. Templin, I. Will
MBI, Berlin, Germany

The successful operation of the Free electron LASer in Hamburg (FLASH) at DESY brings up the interest in further broadening the spectrum of possible applications also for the upcoming European XFEL. Hence the electron beam properties required for lasing should be tested and optimized for a broad range of values already on the level of the injector. The Photo Injector Test facility in Zeuthen (PITZ) at DESY characterizes the photo injectors for FLASH and the European XFEL. The main study involves the transverse projected emittance optimization for different beam conditions. Beside the projected emittance, the PITZ setup allows to measure the transverse emittance with a sub-bunch longitudinal resolution. This slice emittance diagnostics is based on the usage of bunches with an energy correlation of the longitudinal phase space components induced by the booster. Then the bunch is swept vertically with a dipole magnet. Part of the bunch that corresponds to a longitudinal slice is cut out by means of a vertical slit and the horizontal emittance is measured. This report presents the results of recent slice emittance measurements for different bunch charges.

THPC114

High Brightness Photo Injector Upgrade and Experimental Optimization at PITZ

emittance, laser, gun, booster

3152

M. Krasilnikov, H.-J. Grabosch, M. Gross, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
L. Hakobyan, M.A. Khojoyan
YerPhI, Yerevan, Armenia
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
I.I. Isaev, A. Shapovalov
MEPhI, Moscow, Russia
M.A. Nozdrin
JINR, Dubna, Moscow Region, Russia
D. Richter
HZB, Berlin, Germany
I.H. Templin, I. Will
MBI, Berlin, Germany

The photo injector test facility at DESY in Zeuthen (PITZ) develops and optimizes electron sources for linac driven free electron lasers. The main goal of PITZ is to demonstrate a small electron beam emittance by tuning several main parameters of the injector - photo cathode laser pulse, rf gun with solenoids and booster cavity parameters. A slit scan technique is used to measure the transverse phase space of the electron beam and the projected normalized emittance. The photo injector is capable of pulse train production which can be measured with dedicated diagnostics at PITZ. This enables optimization of the beam emittance for a wide range of bunch charges from tens of pC to several nC while keeping high resolution of beam measurements. The results of the experimental optimization will be presented yielding a new benchmark of photo injector performance.

THPC115

Emittance Optimization for Different Bunch Charges with Upgraded Setup at PITZ

emittance, laser, gun, booster

3155

G. Vashchenko, G. Asova, M. Gross, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, M. Krasilnikov, M. Mahgoub, D. Malyutin, M. Otevřel, B. Petrosyan, S. Rimjaem, A. Shapovalov, F. Stephan, S. Weidinger
DESY Zeuthen, Zeuthen, Germany
M.A. Nozdrin
JINR, Dubna, Moscow Region, Russia
D. Richter
HZB, Berlin, Germany
I.H. Templin, I. Will
MBI, Berlin, Germany

The Photo Injector Test facility at DESY, Zeuthen site, (PITZ) has the aim to develop and optimize high brightness electron sources for Free Electron Lasers like FLASH and the European XFEL. Photo electrons emitted from the Cs2Te cathode are accelerated by a 1.6-cell L-band RF gun cavity operated at 60 MV/m maximum accelerating gradient at the cathode. Cylindrically shaped laser pulses with a flat-top temporal profile of about 20 ps FWHM and 2 ps rise and fall time are used to produce electron beams with extremely low emittance. The PITZ beam line was upgraded in 2010. The new gun cavity (prototype number 4.1) was installed January 2010. The new booster cavity (CDS) with well-defined field distribution was installed in July 2010. The diagnostic system for characterization of the laser hitting the photocathode was upgraded in October 2010. Emittance measurements results for different charges: 2 nC, 1 nC, 0.25 nC, 0.1 nC and 0.02 nC, will be presented. The optimization was done for different parameters, e.g. gun solenoid current, gun phase, laser spot size on the cathode, booster gradient.

THPC116

Surface Analysis of a Degraded NEA-GaAs Photocathode by Temperature Programmed Desorption Technique

vacuum, cathode, quadrupole, ion

3158

H. Iijima, M. Kuriki, Y.M. Masumoto
HU/AdSM, Higashi-Hiroshima, Japan

A GaAs photocathode activated the surface to negative electron affinity (NEA) is an important device for high-average-current electron accelerators, such as a next-generation light source based on an energy recovery linac. It is well known that the quantum efficiency of the NEA-GaAs photocathode is decaying with time elapsing, even if the electron beam is not extracted. The degradation is mainly caused by adsorption of residual gases in a vacuum chamber. Previously a few investigators reported that the quantum efficiency of the photocathode was rapidly degraded by water or carbon dioxide vapor. In order to analyze such surface states, we have measured desorption of gases from the degraded NEA-GaAs photocathode by using of temperature programmed desorption (TPD) technique with a quadrupole mass spectrometer. The desorption peaks of hydrogen, carbon oxide and carbon dioxide from the degraded NEA surface were observed, while that of water was not observed.

THPC117

Analysis Quantum Efficiency Spectrum of NEA-GaAs Photocathode

vacuum, cathode, brightness, linac

3161

Y.M. Masumoto, H. Iijima, M. Kuriki
HU/AdSM, Higashi-Hiroshima, Japan

ERL is a future project of synchrotron light source with high brightness and partial coherence. ERL is based on super conducting linear accelerator providing the high brightness electron beam to insertion devices continuously. One of the most difficult technical challenge is the electron source for ERL. A photo-cathode DC biased gun is assumed, but several issues should be solved. One of the issue is the operational lifetime of cathode material, NEA GaAs. NEA stands for Negative electron affinity made by artificial treatment on clean GaAs surface. Emission from the cathode is decreased in time and extracted beam current. In order to research the phenomena, the surface potential is studied by measuring the QE　(Quantum Efficiency) spectrum. Observing temporal evolution of QE, we found that the photon energy threshold did not change during the decay. The spectrum shape was changed suggesting that the surface potential barrier becomes thicker.

THPC118

Present Status of Quantum Radiation Sources on the Basis of the S-band Compact Electron Linac

laser, radiation, cavity, linac

3164

R. Kuroda, E. Miura, H. Toyokawa, K. Yamada, E. Yamaguchi
AIST, Tsukuba, Ibaraki, Japan
M. Kumaki
RISE, Tokyo, Japan

We have developed quantum radiation sources such as a laser Compton scattering (LCS) X-ray and a coherent THz radiation sources on the basis of the S-band compact electron linac at AIST in Japan. The S-band linac consists of the laser-driven photocathode rf gun and two 1.5 m-long acceleration tubes and can accelerate the electron beam up to about 42 MeV. The LCS X-ray source can generate a quasi-monochromatic hard X-ray with variable energy of 12 - 40 keV for medical and biological applications. Now, the multi-collision LCS system has been developed with the regenerative amplifier type laser storage cavity and the multi-bunch electron beam to increase the X-ray yield. On the other hand, the high-power coherent THz radiation source has been also developed and its peak power is estimated to be more than 1 kW in frequency range between 0.1 - 2 THz. The high-power THz radiation was applied to the scanning transmission imaging. Now, the high power THz time domain spectroscopy (TDS) has been developed for the material science. In this conference, we will report the present status of the S-band compact electron linac, our quantum radiation sources and applications.

THPC120

Experimental Investigation of Photocathode Thermal Emittance Components with a Copper Cathode*

emittance, cathode, gun, laser

3167

H.J. Qian, Y.-C. Du, Hua, J.F. Hua, W.-H. Huang, C. Li, C.-X. Tang, L.X. Yan
TUB, Beijing, People's Republic of China

With progress of photocathode RF gun technology, thermal emittance has become the primary limitation of electron beam brightness*. Extensive efforts have been devoted to study thermal emittance, but experiment results diverge between research groups and few can be well interpreted**. One possibility is the undefined online cathode surface conditions, which may cause difference of work functions, field enhancement factor and surface roughness, and lead to thermal emittance divergence. In this paper, we report an experiment of characterizing online photocathode work function, field enhancement factor and surface roughness effect by measuring electric field dependence of photoemission quantum efficiency (QE) and thermal emittance in a Cu-cathode RF gun. Preliminary experiment results reveal huge thermal emittance contributed by surface roughness for the first time, and are in reasonable consistency with theoretical model prediction***.
*Ivan V. Bazarov et al., Phys. Rev. Lett. 10², 104801(2009)
** D.H. Dowell et al, Nucl. Instrum. Methods Phys. Res., Sect. A 622, 685 (2010).
***D. Xinag et al, PAC’07, 10⁴⁹ (2007)

THPC127

Recent Results from a Combined Diode-RF Gun

emittance, cathode, laser, gun

3182

C.H. Gough, S. Ivkovic, M. Paraliev
PSI, Villigen, Switzerland

For the SwissFEL project, a novel combined diode-RF electron gun was tested at PSI, as a possible source for XFELs. Typically, electron bunches of 1-100 pC charge , 1-5 MeV energy and 2-0.3 um-rad emittance were produced and measured. The advantage of the combined gun is that diode geometry and emission surface can be changed readily. An optimum polishing procedure for magnesium photo cathodes was found, and various surfaces such as FEA's were tested in high gradient. Emittance changes for emission surface depression within the cathode, as well as laser spot size and anode hole size, were measured. Finally, the excellent performance of the gun permitted detailed study of the pepperpot EMSY (Emittance Measurement System) behaviour with changing beam parameters.

THPC129

Gallium Arsenide Photocathode Research at Daresbury Laboratory

cathode, laser, vacuum, gun

3185

L.B. Jones, B.D. Fell, J.W. McKenzie, K.J. Middleman, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R.J. Cash
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
N. Chanlek
UMAN, Manchester, United Kingdom

Significant effort has been expended over several years by ASTeC to optimise procedures for preparing GaAs photocathodes for use as high-current electron sources in accelerators. Having established robust chemical and thermal cleaning processes, and carried out lifetime studies on activated photocathodes by deliberately poisoning them*, we present data showing high levels of Quantum Efficiency (QE) for heterostructure photocathodes when activated with Cs-O and Cs-NF3 procedures. We will show that the use of NF3 delivers higher QE, and conveys greater control in that the final QE level can be set more accurately using NF3 than with O. We plan to carry out further experiments on GaAs photocathodes to measure the 2-D energy distribution of the emitted electrons at both room and cryogenic temperatures. We are constructing a retarding-field electron calorimeter which will measure current as a function of retarding voltage. From this, we will establish the 2-D energy distribution in the electron beam, permitting a comparison of these figures for photocathodes at room and low temperatures. The goal is to create an ultra-bright electron source for use with particle accelerators.
* Proc IPAC ’10, TUPEC018, 1752-1754

THPC130

A 160 keV Photocathode Electron Gun Test Tacility

gun, diagnostics, laser, cathode

3188

L.B. Jones, B.D. Fell, C. Hill, J.W. McKenzie, K.J. Middleman, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R.J. Cash
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The ALICE ERL* at Daresbury Laboratory is a prototype 4th generation free-electron laser light source operating at IR wavelengths. An upgrade to the DC photoinjector gun has been designed and partially-constructed, but due to installation postponement, the system will be used for photocathode physics experiments. The re-designed gun will operate at 160 keV. The gun and photocathode preparation facility (PPF) will be assembled with a diagnostic beamline, supporting research towards high-brightness electron beams based on GaAs technology. Combining an external PPF with a load-lock facility allows the rapid exchange of photocathodes, thus permitting the testing of various different photocathode heterostructures, and fine control of the cleaning and activation processes applied during preparation. The diagnostics beamline will include a transverse kicker to study bunch length, and a dipole magnet for beam energy and energy spread measurements. Various horizontal and vertical slit and screen assemblies allow for emittance measurement, so providing full 6-D characterisation of the electron bunches generated. A current transformer and Faraday cups support bunch charge measurements.
* Accelerators and Lasers In Combined Experiments electron Energy-Recovery Linac

THPC133

Pre-Conceptual Design Requirements For The MaRIE Facility At LANL And The Resulting X-Ray Free Electron Laser Baseline Design

photon, linac, scattering, emittance

3197

R.L. Sheffield, B.E. Carlsten
LANL, Los Alamos, New Mexico, USA

The MaRIE (Matter-Radiation Interactions in Extremes) facility is being proposed to advance materials science by the concurrent utilization of a diverse set of highly penetrating probes. These probes will provide the basis for developing materials that will perform predictably and on demand with currently unattainable lifetimes in extreme environments. The MaRIE facilities, the Multi-Probe Diagnostic Hall (MPDH), the Fission and Fusion Materials Facility (F³), and the Making, Measuring, and Modeling Materials (M4) Facility will each have experimental needs for one or more high-energy x-ray beam probes, but all require a 50-keV coherent source of greater than 10¹0 photons in less than 1 ps. Because of space considerations at the facility, a high-gradient design is being investigated that will use a X-band RF systems to drive a 20-GeV normal-conducting linac. Experimental requirements drive a need for multiple photon bunches over time durations greater than 1 microsecond, as well as interleaving 0.1 nC very-low-emittance bunches with 2-nC electron bunches. This paper will cover an overview of the scientific requirements for the MaRIE XFEL and the baseline XFEL design.

THPC134

LCLS RF Gun Copper Cathode Performance

cathode, laser, gun, emittance

3200

A. Brachmann, F.-J. Decker, P. Emma, R.H. Iverson, P. Stefan, J.L. Turner, F. Zhou
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE-AC03-76SF00515
We report on the performance and the operational experience of the LCLS RF gun copper photocathodes used during the LCLS run I, II, III and IV. We discuss the problems of cathode surface contamination and our experience with methods to remove such contamination. Techniques to obtain high quantum efficiency (QE) while preserving the low emittance quality are discussed. Furthermore, we will present the current status of the installed cathode, its quantum efficiency and the typical injector emittances of the extracted beam.

THPC135

Optimal Parameters of the Photocathode Gun Space Charge to Improve Beam Quality

laser, cathode, gun, space-charge

3203

M.G. Fedurin, C. Swinson, V. Yakimenko
BNL, Upton, Long Island, New York, USA

Accelerator Test Facility at Brookhaven National Laboratory operates with 5 MeV photocathode gun and 70 MeV linac for different range of experiments with a few picoseconds and a few micrometers emittance electron bunch. Many conducted experiments require beam with good spatial resolution and short length as well. NdYaG laser pulse turns to the electron bunch in the gun with space charge affecting on the own bunch length and transverse profile. Optimal beam loading parameters of the space charge in the photocathode RF gun could be found and used to improve bunch length and emittance. Simple model and experimental results on the Accelerator Test Facility at Brookhaven national Laboratory will be described

THPC142

Burst Pulse Superimposed Electron Beam Acceleration in LEBRA FEL Linac

FEL, acceleration, linac, gun

3218

T. Tanaka, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, N. Sato
LEBRA, Funabashi, Japan
S. Aizawa, Y. Arisumi, K. Shinohara
Nihon Koshuha Co. Ltd, Yokohama, Japan
I. Sato
Nihon University, Advanced Research Institute for the Sciences and Humanities, Funabashi, Japan

The electron beam for free electron laser (FEL) at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University had been extracted from a conventional DC triode electron gun system. In conjunction with the renewal of the gun high voltage terminal a Kentech high-speed grid pulser was installed in addition to the conventional grid pulser. The 89.25MHz sine wave frequency-divided from the 2856MHz accelerating RF has been applied to the high-speed grid pulser, generating 64 or 128 frequency-divided grid pulses synchronous with the round-trip time in the FEL optical resonator. The high-speed grid pulses have been applied to the EIMAC Y646B cathode simultaneously with the conventional macropulse through the pulse coupling strip-line circuit; the resultant beam has been the short pulse beam superimposed on the macropulse beam. By reducing the macropulse voltage, only the train of the burst beam with 0.6ns width has been extracted. The peak burst beam current roughly 6 times higher than the conventional macropulse beam has been obtained with the Farady cup at the end of the FEL beamline. The FEL lasing experiment with the burst beam is underway.

THPC151

The 65 mm Period Electromagnetic/Permanent Magnets Helical Undulator at SOLEIL

permanent-magnet, undulator, power-supply, wiggler

3239

F. Marteau, P. Berteaud, F. Bouvet, L. Chapuis, M.-E. Couprie, J.P. Daguerre, T.K. El Ajjouri, J.-M. Filhol, P. Lebasque, J.L. Marlats, A. Mary, K. Tavakoli
SOLEIL, Gif-sur-Yvette, France

SOLEIL prepares a new 65 mm period Electromagnetic/Permanent Magnets Helical Undulator (EMPHU), with a rapid switching at 5 Hz of the polarization required for dichroïsm experiments. The vertical field Bz is produced by coils fed by a fast switching power supply (designed and built in house), with a maximum current of 350 A and a polarity switching time shorter than 100 ms. The coils consist of 25 stacked copper layers shaped by water jet cutting. The current flows in 16 layers and 9 of them are cooled with thermal drain to a water piping. 4 additional power supplies feed 2 types of correction coils for the dynamic compensation of the field integrals, besides the ones for the termination. 1.28 T remanence NdFeB permanent magnets generate the horizontal field Bx. Peak Bz and Bx in the helical configuration reach 0.24 T at 14.7 mm minimum gap. Thermal modelling and measurements aim at keeping the magnet temperature constant. The static magnetic configuration was optimised using the ID_Builder software and the trajectory were checked for insuring a good reproducibility of the photon beam pointing when sweeping from one helicity to the other.

THPC154

Shimming of the Dynamic Field Integrals of the BESSY II U125 Hybrid Undulator

undulator, wiggler, permanent-magnet, injection

3248

J. Bahrdt, W. Frentrup, A. Gaupp, M. Scheer, I. Schneider, G. Wüstefeld
HZB, Berlin, Germany

Within a continuous program the BESSY II undulators are prepared for Topping-Up operation. The BESSY II U125 planar hybrid undulator has a period length of 125 mm and a pole width of only 60 mm. The horizontal defocusing of the 1.7 GeV e-beam may result in a significant reduction of the horizontal dynamic aperture, reducing the injection efficiency when injecting into the closed gap. The dynamic field integrals are derived from a 2D-Fourier decomposition of the 3D-field. An analytic description of the dynamic multipoles based on the Fourier coefficients is presented. Magic fingers have been installed in order to minimize the dynamic field integrals and to enlarge the good field region of the device.

THPC159

Factory Acceptance Test of COLDDIAG: A Cold Vacuum Chamber for Diagnostics

vacuum, diagnostics, synchrotron, factory

3263

S. Gerstl, T. Baumbach, S. Casalbuoni, A.W. Grau, M. Hagelstein, T. Holubek, D. Saez de Jauregui
Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
V. Baglin
CERN, Geneva, Switzerland
C. Boffo, G. Sikler
BNG, Würzburg, Germany
T.W. Bradshaw
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
R. Cimino, M. Commisso, A. Mostacci, B. Spataro
INFN/LNF, Frascati (Roma), Italy
J.A. Clarke, R.M. Jones, D.J. Scott
Cockcroft Institute, Warrington, Cheshire, United Kingdom
M.P. Cox, J.C. Schouten
Diamond, Oxfordshire, United Kingdom
I.R.R. Shinton
UMAN, Manchester, United Kingdom
E.J. Wallén
MAX-lab, Lund, Sweden
R. Weigel
Max-Planck Institute for Metal Research, Stuttgart, Germany

Superconductive insertion devices (IDs) have higher fields for a given gap and period length compared with the state-of-the-art technology of permanent magnet IDs. One of the still open issues for the development of superconductive insertion devices is the understanding of the heat intake from the electron beam. With the aim of measuring the beam heat load to a cold bore and the hope to gain a deeper understanding in the underlying mechanisms, a cold vacuum chamber for diagnostics was built. It is equipped with the following instrumentation: retarding field analyzers to measure the electron flux, temperature sensors to measure the beam heat load, pressure gauges, and mass spectrometers to measure the gas content. The flexibility of the engineering design will allow the installation of the cryostat in different synchrotron light sources. The installation in the storage ring of the Diamond Light Source is foreseen in November 2011. Here we report about the technical design of this device, the factory acceptance test and the planned measurements with electron beam.

THPC164

Phase Shifters for the FERMI@Elettra Undulators

undulator, FEL, radiation, polarization

3278

B. Diviacco, R. Bracco, D. Millo, M.M. Musardo
ELETTRA, Basovizza, Italy

The variable gap undulator system in operation at the FERMI@Elettra Free Electron Laser facility requires adjustable phase matching devices between consecutive radiator segments in order to maintain optimal lasing conditions while changing the radiation properties. A permanent magnet phase shifter has been designed to achieve the required electron beam delay in a compact structure that could be installed in close proximity to the undulators. In this paper we present the design of the phasing units and the results of the magnetic measurements performed on the five devices installed so far. We also describe the method used to properly set their field strength for any given electron energy, radiation wavelength and polarization.

THPC165

Estimations for Demagnetization of ID Permanent Magnets due to Installation of OTR

permanent-magnet, radiation, simulation, undulator

3281

Y. Asano
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Bizen
JASRI/SPring-8, Hyogo, Japan

Demagnetization due to high energy electron irradiation is one of the crucial issues for stable operation of X-ray free electron laser (XFEL) and Synchrotron radiation (SR) facilities. Especially, during the commissioning, electron beam is scattered and then hits permanent magnets of insertion devices due to installation of some instrumentations such as OTR (Optical Transition Radiation) for beam diagnosis so that the estimation of demagnetization is very important to perform the commissioning smoothly. Fortunately, we found the index of demagnetization of Nd2Fe14B permanent magnets due to high energy electron irradiation. Star density produced by high energy photo-neutron reproduces experimental results of demagnetization. At SPring-8, in-vacuum type undulators have been employed for XFEL so that we estimate the demagnetization of the undulators for various cases such as electron energy in ranging from 2 GeV to 8 GeV and the permanent magnet gap from 2 mm to 40 mm. And we also estimate the allowable time to be able to insert the OTR.

THPC168

Field Error Correction for a Superconducting Undulator

undulator, photon, radiation, simulation

3290

S. Chunjarean
PAL, Pohang, Kyungbuk, Republic of Korea
C.-S. Hwang, J.C. Jan
NSRRC, Hsinchu, Taiwan
H. Wiedemann
SLAC, Menlo Park, California, USA

To reach higher photon energies in the region of soft or hard x-rays with high photon beam brightness in low energy storage rings, superconducting undulators with very short period length and high magnetic field strength are required. Because undulator radiation comes in a line spectrum, photons up to the 7th harmonic are desired. The photon brightness in such harmonics is strongly dependent on perfect periodicity of the magnetic field. Such imperfections also appear in conventional permanent material undulators, which can be corrected by well developed and efficient shimming. Unfortunately, this method cannot be applied to superconducting undulators. Therefore, we present a new approach to field corrections by modification of the magnetic field saturation in each pole. In this paper it is shown that this approach can reduce not only the magnetic field error but also greatly improves phase errors from period to period. The proposed method works quite local with only small perturbations in neighboring poles. The tenability is preserved for most of the field excitations and is reduced only at extreme parameters.

THPC169

Short-Period RF Undulator for a Nanometer SASE Source

undulator, cavity, injection, radiation

3293

S.V. Kuzikov, M.E. Plotkin, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia
J.L. Hirshfield
Yale University, Physics Department, New Haven, CT, USA
T.C. Marshall, G.V. Sotnikov
Omega-P, Inc., New Haven, Connecticut, USA

Funding: Sponsored in part by US Department of Energy, Office of High Energy Physics.
A room-temperature RF undulator to produce ~1 nm wavelength radiation using a relatively low energy electron beam (0.5 GeV) is considered. The design features include an effective undulator period of 0.45 cm, an undulator parameter of K = 0.4, an effective field length of 50 cm. These parameters could be be realized using a multi-MW RF power amplifier to drive the undulator (e.g., the 34 GHz pulsed magnicon at Yale or a 30 GHz gyroklystron at IAP) with microsecond pulse duration. Two undulator designs were considered that avoid problems with a co-propagating wave: a dual-mode cylindrical cavity [TE01 (counter propagating) - TE02 (co-propagating)] with an off-axis electron beam; and a traveling HE11 mode resonant ring with an on-axis beam.

THPC172

Superconducting 119-pole Wiggler for ALBA Light Source

wiggler, vacuum, site, radiation

3302

N.A. Mezentsev, S.V. Khrushchev, V.K. Lev, E.G. Miginsky, V.A. Shkaruba, V.M. Syrovatin, V.M. Tsukanov, A.A. Volkov
BINP SB RAS, Novosibirsk, Russia
J. Campmany, D. Einfeld
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain

Budker INP of Siberian Branch of the Russian Academy of Science has designed, manufactured and tested 119-pole superconducting wiggler for ALBA CELLS light source. The period length and maximal field of the wiggler are 30 mm 2.2 Ò correspondingly. Pole gap and vertical aperture for electron beam are 12.6 mm and 8.5 mm, accordingly. The wiggler magnetic structure closely comes nearer to undulator structure as K-value is about 6. The wiggler cryostat is bath cryostat type with use of cryocoolers which provide zero liquid helium consumption for long period. In June, 2010 the wiggler has been successfully tested on ALBA site. Test results of the wiggler including magnetic measurement, quench training, cryogenic system behavior for various mode of operation are presented.

THPC174

Manufacturing and Testing of the First Phase Shifter Prototypes Built by CIEMAT for the European-XFEL

controls, undulator, free-electron-laser, laser

3308

I. Moya, J. Calero, J.M. Cela-Ruiz, L. García-Tabarés, A. Guirao, J.L. Gutiérrez, L.M. Martinez Fresno, T. Martínez de Alvaro, E. Molina Marinas, A.L. Pardillo, L. Sanchez, S. Sanz, F. Toral, C. Vazquez, J.G.S. de la Gama
CIEMAT, Madrid, Spain

Funding: Work partially supported by the Spanish Ministry of Science and Innovation under SEI Resolution on 17-September-2009.
The European X-ray Free Electron Laser (EXFEL) will be based on a 10 to 17.5 GeV electron linac. Its beam will be used in three undulator systems to obtain ultra-brilliant X-ray flashes from 0.1 to 6 nanometres for experimentation. The undulator systems are formed by 5m long undulator segments and 1.1m long intersections in between. They accommodate a quadrupole on top of a precision mover, a beam position monitor, two air coil correctors and a phase shifter. The function of the phase shifter is to adjust the phase of the electron beam with respect to that of the radiation field when the wavelength is changed by tuning the gap. In this context, CIEMAT will deliver 92 phase shifters, as part of the Spanish in-kind contribution to the EXFEL project. This paper describes the engineering design, the manufacturing techniques and the mechanical and magnetic tests realized on the first prototypes.

THPC177

Field Correction Results from NSRRC Elliptically Polarized Undulator 46

kicker, undulator, multipole, synchrotron

3317

J.C. Huang, C.-H. Chang, C.-S. Hwang, C. JunTune, F.-Y. Lin
NSRRC, Hsinchu, Taiwan

Elliptically polarized undulator (EPU) is a common insertion device to use in storage ring in order to provide circular polarization. The field correction is an essential step for EPU construction, and it can prevent the photon flux reduction from idea case and electron beam trajectory and exit angle from EPU. The conventional field correction method is tedious works and strongly based on experiences. An initial state of NSRRC EPU46 has phase error over 40 degrees, and many difficulties on field correction to reduce the phase error under 5 degrees. This paper will describe the detailed magnetic field correction process and practical results from in NSRRC EPU.

THPC179

Electron Beam Heating and Operation of the Cryogenic Undulator and Superconducting Wigglers at Diamond

wiggler, undulator, cavity, synchrotron

3323

J.C. Schouten, E.C.M. Rial
Diamond, Oxfordshire, United Kingdom

Diamond Light Source has two superconducting wigglers and one cryocooled undulator installed serving three beam lines. The cryocooled undulator (cpmu) has been operating since August 2010 while the superconducting wigglers have been operating for more than 4 years (SCW-1) and 2 years (SCW-2). We will report on the first year of operation of the cpmu including details of its spectral output and cryogenic performance. Our experience of the cooling system and measures taken to ensure reliability and to minimize the risks of a prolonged downtime are also presented. The two superconducting wigglers are exposed to a high heat load due to the beam heating of the inner liner. Until recently this resulted in a much higher helium consumption than specified and so recently a new liner has been fitted to SCW-1 and new re-condensers to SCW-2. In addition a thermal bridge has been made between the RF tapers and the outer heat shield of both SCW-1 and SCW-2. The results of these improvements will be presented.

THPC183

Application of the Balanced Hybrid Mode in Overmoded Corrugated Waveguides to Short Wavelength Dynamic Undulators

undulator, cavity, impedance, FEL

3326

S.G. Tantawi, G.B. Bowden, C. Chang, J. Neilson, M. Shumail
SLAC, Menlo Park, California, USA
C. Pellegrini
UCLA, Los Angeles, California, USA

Funding: Work Supported by the US Department of Energy
Inspired by recent developments in low-loss overmoded components and systems for ultra-high power RF systems, we explored several overmoded waveguide systems that could function as RF undulators. One promising structure is a corrugated waveguide system operating at the hybrid HE11 mode. This is a new application for that mode. Initial calculations indicate that such a system can be operated at relatively low power levels while obtaining large values for the undulator parameters. RF surface fields are typically low enough to permit superconducting operation. This technology could realize an undulator with short wavelengths and also dynamic control of the undulator parameters including polarization. We introduce the scaling laws governing such a structures, and then show with exact simulations an undulator design that have a wavelength of about 1.4 cm with an undulator parameter K~1. This undulator is intended to be powered by a 50 MW source at a frequency of 11.4 GHz. We describe the experimental setup for testing such a technology.

THPC184

Progress of the Coherent Soft X Ray Straight Section at NSLS-II

undulator, photon, polarization, insertion

3329

C.A. Kitegi, P. Cappadoro, O.V. Chubar, T.M. Corwin, D.A. Harder, P. He, Y. Li, C. Meyer, G. Rakowsky, J. Rank, C. Rhein, C.J. Spataro, T. Tanabe
BNL, Upton, Long Island, New York, USA

The National Synchrotron Light Source II (NSLS-II) is the new light source under construction at Brookhaven National Laboratory (BNL). The Coherent Soft X rays beam line (CSX) is one of the six beamlines included in the baseline project. Following the request of CSX scientists for a source providing adjustable polarized radiation from 160 eV to 1.7 keV, two Advanced Planar Polarized Light Emitter II (APPLE-II)-type undulators will be installed in a 6.6 m long straight section. Each device is 2 m long, the period is 49.2 mm and the minimum gap is 11.5 mm. The different operation modes of the beamline and the layout of the straight section are reviewed here.

THPO004

An Active Power Filter Based on Wavelet Analysis

power-supply, controls, simulation, background

3341

X.L. Guo
Private Address, Beijing, People's Republic of China
X.L. Guo
IHEP Beijng, Beijing, People's Republic of China

As modern accelerator demands a magnet supply with a much higher stability, it is important to improve the quality of the magnet supply. An effective method to improve the output performance active power filter (APF) applied in current supply is proposed. To lowdown the harmonic constituents, the APF circuit generates a harmonic current, which added to the current from the main power supply, to countervail the ones in the supply’s current. At end of this paper, a simulation result is given to prove the effect of APF.

THPO025

Longitudinal Beam Dynamics of a Laser Sliced Bunch

laser, synchrotron, radiation, damping

3397

P. Kuske
HZB, Berlin, Germany

Nowadays fs-laser slicing of a bunch of electrons in storage rings is quite common for creating short VUV- and soft X-ray light pulses or pulses of coherently emitted THz-radiation over a couple of revolutions. In this paper the longitudinal dynamics of the sliced bunch is studied numerically. The calculations are based on the one dimensional solution of the Vlasov-Fokker-Planck-equation assuming that the shielded CSR-wake is dominating the dynamics of the 100 fs-long slice. It is found that the density modulation survives longer and that the CSR-spectra extend to higher frequencies at later turns even below the corresponding instability threshold. This very simple model seems to support experimental observations at the Swiss Light Source.

THPO029

Microwave Beating Generated by a Dual Beam Accelerator

beat-wave, plasma, coupling, impedance

3406

G.L. Li, Z.X. Jin, L. Liu, T. Shu, J.H. Yang, C.W. Yuan, J. Zhang
National University of Defense Technology, Changsha, Kaifu District, People's Republic of China

Funding: National University of Defense Technology
As high power microwave (HPM) technologies gradually matured, the technologies for enhancing the output capacity of HPMs are becoming more and more attractive. However, limited by physics and technology, the approaches for enhancing the output capacity with a single HPM source have encountered difficulties. An alternative method for enhancing the output capacity of HPM sources is the coupling output of dual channel HPM sources. However, if the microwave sources have some coupling with each other, they maybe inter modulate with each other, and the phase-locking of the HPM sources may occur. In order to make sure that the beat waves are generating on the right way, a waveguide diplexer is introduced. Each channel has disjoint pass frequency band, and dual-channel HPM sources are isolated. As the dual-channel electron beams are driven by one accelerator, the HPM sources are expected to have a better match with the accelerator, and even higher microwave power is possible. In the high power experiments, the radiated powers of the beat waves are measured to be about 4.3 GW, 40 ns, the frequencies are about 9.41 GHz and 9.59 GHz.
Correspondence: Guolin Li, College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China. Email: nudt-liguolin@hotmail.com

THPO035

Computer Investigation of Efficiency Enhancement in Coaxial Gyrotron Backward Wave Oscillators

simulation, plasma, injection, bunching

3418

V.M. Khoruzhiy
NSC/KIPT, Kharkov, Ukraine

The gyrotron backward wave oscillator (gyro-BWO) is a high frequency (HF) powerful oscillator for cm and mm wavelengths*,**,***.Gyro-oscillators are possible devices for accelerators techniques. For efficiency enhancement in gyro-devices we suggest profiling of guiding magnetic field Hg(z) at longitudinal direction z by special law, namely Hg(z)=Hg0*(1+alfa*(z/L)*f(z/L))**0.5 where Hg0 is amplitude of homogenous guiding magnetic field, alfa is non-homogeneity amplitude, L is waveguide length and function f(z/L))is similarly to the shape (envelope) of longitudinal distribution of HF electrical field E(z) in gyro-device along longitudinal coordinate z. For investigated gyro-BWO f(z/L)=(cos(pi*z/2L))**m, f(0)=1, f(L)=0, L=60cm, m=6 and pi=3.14. We obtained enhancing of gyro-BWO’s efficiency from 11% (homogenous distribution of guiding magnetic field) up to 32% (non-homogenous one) due to profiling of magnetic field under conditions above.
* A.V.Gaponov et al., Izv. VUZov(USSR), Radiofizika 10(9), 10, 1967.
** V.Khoruzhiy et al., Phys. J.of Ukraine 49(2), 126, 2004.
*** V.Khoruzhiy et al., Phys. J.of Ukraine 50(11), 1230, 2005.

THPS002

Progress of the 2 MeV Electron Cooler Development for COSY-Jülich/HESR

solenoid, high-voltage, dipole, proton

3427

J. Dietrich, V. Kamerdzhiev
FZJ, Jülich, Germany
M.I. Bryzgunov, A.D. Goncharov, V.M. Panasyuk, V.V. Parkhomchuk, V.B. Reva, D.N. Skorobogatov
BINP SB RAS, Novosibirsk, Russia

The 2 MeV electron cooling system for COSY-Jülich was proposed to further boost the luminosity even in presence of strong heating effects of high-density internal targets. The project is funded since mid 2009. The design and construction of the cooler is accomplished in cooperation with the Budker Institute of Nuclear Physics in Novosibirsk, Russia. The 2 MeV cooler is also well suited in the start up phase of the High Energy Storage Ring (HESR) at FAIR in Darmstadt. It can be used for beam cooling at injection energy and is intended to test new features of the high energy electron cooler for HESR. The infrastructure necessary for the operation of the cooler in the COSY ring (radiation shielding, cabling, water cooling etc.) is established. The electron beam commissioning at BINP Novosibirsk is scheduled to start at May of 2011. First results are reported. Final commissioning at COSY-Jülich is planned for the end of 2011.

THPS004

Beam Dynamics Simulation on Simultaneous use of Stochastic Cooling and Electron Cooling with Internal Target

emittance, target, simulation, proton

3433

T. Kikuchi, N. Harada, T. Sasaki, H. Tamukai
Nagaoka University of Technology, Nagaoka, Niigata, Japan
T. Katayama
GSI, Darmstadt, Germany

The small momentum spread of proton beam has to be realized and kept in the storage ring during the experiment with a dense internal target. The stochastic cooling alone does not compensate the momentum spread increases due to the scattering at the internal target. The dense proton beam in the six dimensional phase space includes intra-beam scattering as one of emittance growth mechanisms. The numerical simulation is carried out using Fokker-Planck equation solver, and the results on the simultaneous use of stochastic cooling and electron cooling at COSY are indicated.

THPS006

Present Status of Beam Cooling and Related Research at S-LSR

laser, proton, ion, betatron

3436

A. Noda, M. Nakao, H. Souda, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
T. Fujimoto, S.I. Iwata, S. Shibuya
AEC, Chiba, Japan
M. Grieser
MPI-K, Heidelberg, Germany
K. Ito, H. Okamoto
HU/AdSM, Higashi-Hiroshima, Japan
K. Jimbo
Kyoto IAE, Kyoto, Japan
K. Noda, T. Shirai
NIRS, Chiba-shi, Japan

Funding: Work supported by Advanced Compact Accelerator Development project of MEXT, and Global COE Program, "The Next Generation of Physics, Spun from Universality and Emergence" at Kyoto University.
With the use of Ion Storage and Cooler Ring, S-LSR at ICR, Kyoto University, Mg ion beam with 40 keV has been laser cooled not only in the longitudinal direction but also in the horizontal direction by "Synchro-Betatron Coupling". Laser cooling is now tried to be extended to vertical direction with horizontal and vertical coupling with the use of a solenoid magnetic field. At S-LSR, an electron beam cooling is also applied for 7MeV proton beam, resulting an ordered state. Electron beam cooling is also applied for rf captured bunched beam and a short pulse proton beam with the duration of ~3 ns is fast extracted in order to enable beam irradiation. A beam course is now being constructed to irradiate bio-molecular cells vertically from the bottom through a thin film separating the accelerator vacuum from the cultivating liquid containing the cells in the air.

THPS009

Coherent Electron Cooling Demonstration Experiment

ion, FEL, hadron, wiggler

3442

V. Litvinenko, S.A. Belomestnykh, I. Ben-Zvi, J. Bengtsson, A.V. Fedotov, Y. Hao, D. Kayran, G.J. Mahler, W. Meng, T. Rao, T. Roser, B. Sheehy, R. Than, J.E. Tuozzolo, G. Wang, V. Yakimenko
BNL, Upton, Long Island, New York, USA
G.I. Bell, D.L. Bruhwiler, V.H. Ranjbar, B.T. Schwartz
Tech-X, Boulder, Colorado, USA
A. Hutton, G.A. Krafft, M. Poelker, R.A. Rimmer
JLAB, Newport News, Virginia, USA
M.A. Kholopov, P. Vobly
BINP SB RAS, Novosibirsk, Russia

Coherent electron cooling (CEC) is considered to be on of potential candidates capable of cooling high-energy, high-intensity hadron beams to very small emittances. It also has a potential to significantly boost luminosity of high-energy hadron-hadron and electron-hadron colliders. In a CEC system, a perturbation of the electron density caused by a hadron is amplified and fed back to the hadrons to reduce the energy spread and the emittance of the beam. Following the funding decision by DoE office of Nuclear Physics, we are designing and building coherent electron cooler for a proof-of-principle experiment at RHIC to cool 40 GeV heavy ion beam. In this paper, we describe the layout of the CeC installed into IP2 interaction region at RHIC. We present the design of the CeC cooler and results of preliminary simulations.

THPS012

Simulation of the Generation and Transport of Laser-Accelerated Ion Beams

ion, target, laser, simulation

3445

O. Boine-Frankenheim, V. Kornilov
GSI, Darmstadt, Germany
L. Zsolt
TEMF, TU Darmstadt, Darmstadt, Germany

In the framework of the LIGHT project a dedicated test stand is under preparation at GSI for the transport and focusing of laser accelerated ion beams. The relevant acceleration mechanism for the parameters achievable at the GSI PHELIX laser is the TNSA (Target Normal Sheath Acceleration). The subsequent evolution of the ion beam can be described rather well by the isothermal plasma expansion model. This model assumes an initial dense plasma layer with a 'hot' electron component and 'cold' ions. We will present 1D and 2D simulation results obtained with the VORPAL code on the expansion of the beam and on the cooling down of the neutralizing electrons. The electrons and their temperature can play an important role for the focusing of the beam in a solenoid magnet, as foreseen in the GSI test stand. We will discuss possible controlled de-neutralization schemes using external magnet fields.

THPS034

Studies on Electron Cloud Dynamics for an Optimized Space Charge Lens Design

plasma, space-charge, ion, diagnostics

3493

K. Schulte, M. Droba, B. Glaeser, S. Klaproth, O. Meusel, U. Ratzinger
IAP, Frankfurt am Main, Germany

Funding: Work supported by HIC for FAIR.
Space charge lenses using a stable electron cloud for focusing low energy heavy ion beams are an alternative concept to conventional ion optics. Due to external fields electrons are confined inside the lens’ volume. In case of a homogeneously distributed electron cloud the linear electric space charge field enables beam focusing free of aberration. Since the mapping quality of the lens is related to the confinement, non-destructive diagnostics has been developed to determine the plasma parameters and to characterize the collective behavior of the confined nonneutral plasma. Moreover, a scaled up space charge lens was constructed for a detailed investigation of the nonneutral plasma properties as well as beam interactions with a stable confined electron cloud. Experimental results will be presented in comparison with numerical simulations.

THPS064

Application of X-band 3.95 MeV Linac X-ray Source for On-site Bridge Inspection

linac, site, target, gun

3571

H.F. Jin, K. Demachi, K. Dobashi, T. Fujiwara, M. Uesaka, H. Zhu
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan

We developed an X-ray non-destructive (NDT) system for on-site bridge inspection. A portable X-band (9.3-12 GHz) 3.95MeV linear accelerator (linac) has been developed for this system. The system consists of X-ray of 62kg without the target collimeter of 80kg, the RF power source of 62kg and other utility box of 116kg. For the onsite investigation, a flexible waveguide is used for this linac. And the linac is a point X-ray source. For X-ray detection, we chose 8-inch square size scintillation type flat panel detector. The spatial resolution of the detector is as high as 0.2mm, which is manufactured by Perkin Elmer Co. Cd2O2S:Tb is used for the scintillator crystal. The capable radiation energy range is 40keV to 15MeV. In order to realize quick inspection for a bridge, remote control robot which handles and compact X-ray source and detector are desired. Therefore, we developed 3D location system for this robot. The locating system is realized with image processing with its camera. For the operation, stereoscopic radiographic image is taken and analyzed, and computed tomography (CT) image analysis is taken for detailed inspection.
Non-destructive test (NDT) , X-ray Source, X-band, Linac, Detector, Computed Tomography (CT).

THPS083

Two-channel Mode of Mo-99 Production at an Electron Accelerator

target, neutron, simulation, photon

3627

V.L. Uvarov, A.N. Dovbnya, V.V. Mytrochenko, V.I. Nikiforov, S.A. Perezhogin, V.A. Shevchenko, B.I. Shramenko, A.Eh. Tenishev, A.V. Torgovkin
NSC/KIPT, Kharkov, Ukraine

High-energy bremsstrahlung is the main source of isotopic target activation at an electron accelerator. The photoneutrons concurrently generated are generally considered as a background radiation. At the same time, the natural materials entering into photonuclear targets sometimes comprise a mixture of stable isotopes, the atomic-number difference of which equals 2. Thus, if the desired isotope has an intermediate mass, then at certain conditions, it can be produced on two target nuclei at once, via (γ,n) and (n,γ) channels. As an example, we investigate the possibility of increasing the yield of 99Mo by means of its simultaneous production from 100Mo(γ,n)99Mo and 98Mo(n,γ)99Mo reactions. The method and the device have been developed to provide measurements of the 99Mo yield from the natural molybdenum target as it is placed inside the neutron moderator and without the latter. Experiments were performed at the NSC KIPT accelerator LU-40m at electron energies ranging from 30 to 60 MeV. It is demonstrated that the use of the moderator gives nearly a 30% increase in the 99Mo yield. The experimental results are in good agreement with the computer simulation data.

THPS084

Modification of the PENELOPE Transport System for HS Simulation of Isotope Production Mode

target, simulation, photon, radiation

3630

V.L. Uvarov, V.I. Nikiforov
NSC/KIPT, Kharkov, Ukraine

A method has been developed for high-speed computing the photonuclear isotope yield along with the absorbed radiation power in exit devices of electron accelerator. The technique involves a step-by-step calculation of isotope microyield along the photon trajectories. The approach has been realized in the computer programs based on the PENELOPE system of -2001, -2006 and -2008 versions. For their benchmarking, use has been made of the experimental data on activity distributions of the 67Cu produced from 68Zn(γ,p)67Cu reaction in thick zinc targets. The results of simulation using the PENELOPE-2006 and -2008 codes are in excellent agreement with all experimental data. At the same time, the PENELOPE-2001 computations give good agreement with the experimental results for target activation by the electron beam, but systematically underestimate (~15%) in case of the target exposed to bremsstrahlung. The proposed technique provides a ~ 10⁴ times higher computation speed as compared with the direct Monte Carlo simulation of photonuclear events and that speed is independent of the reaction cross section.

THPS090

Development of the Pulse Radiolysis System with a Supercontinuum Radiation using Photonic Crystal Fiber

laser, radiation, gun, optics

3645

K.B. Ogata, R. Betto, Y. Hosaka, Y. Kawauchi, K. Sakaue, T. Suzuki, M. Washio
RISE, Tokyo, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690
In usage of radiation, it is important to study the process of chemical effects of ionizing radiation in a material. Pulse radiolysis is a method to trace these rapid initial chemical reactions by ionizing radiation. As a pump beam, we are using 5MeV electron beam produced from the S-band photo cathode RF-Gun. In nanosecond timescale pulse radiolysis, it is required the stable probe light of a broad spectrum. And especially in picosecond timescale pulse radiolysis, probe light should have short pulse width to use stroboscopic method. Therefore, in order to develop a wide range of timescale experimental system, we have been developing a Supercontinuum (SC) light as a probe light, which is generated by nonlinear optical process of short pulse IR laser in photonic crystal fiber (PCF). As a result, the SC light spectrum is broad enough to use as a probe light. Then we tried to measure the absorption spectrum of hydrated electron by SC light, we successfully observed good signal-noise ratio data both nanosecond and picosecond experiment with unified pulse　radiolysis system. In this conference, we will report details of these results and future prospects.

THPS095

Q-factor of an Open Resonator for a Compact Soft X-ray Source based on Thomson Scattering of Stimulated Coherent Diffraction Radiation

cavity, radiation, vacuum, scattering

3657

A.S. Aryshev, S. Araki, M.K. Fukuda, J. Urakawa
KEK, Ibaraki, Japan
V. Karataev
JAI, Egham, Surrey, United Kingdom
G.A. Naumenko
Tomsk Polytechnic University, Nuclear Physics Institute, Tomsk, Russia
A. Potylitsyn, L.G. Sukhikh, D. Verigin
TPU, Tomsk, Russia
K. Sakaue
RISE, Tokyo, Japan

High-brightness and reliable sources in the VUV and the soft X-ray region may be used for numerous applications in such areas as medicine, biology, biochemistry, material science, etc. We have proposed a new approach to produce the intense beams of X-rays in the range of eV based on Thomson scattering of Coherent Diffraction Radiation (CDR) on a 43 MeV electron beam. CDR is generated when a charged particle moves in the vicinity of an obstacle. The radiation is coherent when its wavelength is comparable to or longer than the bunch length. The CDR waves are generated in an opened resonator formed by two mirrors. In this report the status of the experiment, the first CDR measurements at the multibunch beam of the LUCX facility and general hardware design will be reported.

THPS098

Compact Gamma-ray Source for Non-destructive Detection of Nuclear Material in Cargo

laser, microtron, photon, neutron

3663

R. Hajima
JAEA/ERL, Ibaraki, Japan
I. Daito, T. Hayakawa, Y. Hayashi, M. Kando, H. Kotaki
JAEA, Kyoto, Japan
T. Hori, H. Ohgaki
Kyoto IAE, Kyoto, Japan
N. Kikuzawa
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
T. Shizuma
JAEA APRC, Ibaraki-ken, Japan

Funding: This work is supported by Strategic Funds for Promotion of Science and Technology (Grant No. 066).
A mono-energetic gamma-ray source based on laser Compton scattering is under development for non-destructive detection of nuclear material in cargo. In the detection system, we employ nuclear resonance fluorescence triggered by mono-energetic gamma-rays tuned at the resonance energy of nuclear material such as U-235. As a prototype, a 150-MeV microtron combined with a YAG laser to produce a 400-keV gamma ray is constructed at JAEA, where critical technologies are to be demonstrated for high-flux gamma-ray generation, 3x10⁵ ph/s. We also start to design a microtron at higher energy, 250 MeV, to produce a 2-MeV gamma-ray, which is required for the detection of U-235.

THPS101

Present and Perspectives of the Sparc THz Source

radiation, linac, polarization, single-bunch

3669

E. Chiadroni, M. Bellaveglia, M. Boscolo, M. Castellano, G. Di Pirro, M. Ferrario, G. Gatti, E. Pace, C. Vaccarezza
INFN/LNF, Frascati (Roma), Italy
P. Calvani, S. Lupi, A. Nucara
Università di Roma I La Sapienza, Roma, Italy
L. Catani, B. Marchetti
INFN-Roma II, Roma, Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
O. Limaj
University of Rome La Sapienza, Rome, Italy
A. Mostacci, L. Palumbo
Rome University La Sapienza, Roma, Italy
C. Ronsivalle
ENEA C.R. Frascati, Frascati (Roma), Italy

The development of radiation sources in the THz spectral region has become more and more interesting because of the peculiar characteristics of this radiation: it is non ionizing, it penetrates dielectrics, it is highly absorbed by polar liquids, highly reflected by metals and reveals specific "fingerprint" absorption spectra arising from fundamentals physical processes. The THz source at SPARC is an accelerator based source for research investigations (e.g. material science, biology fields). Its measured peak power is of the order of 10⁸ W, very competitive with respect to other present sources. The present status of the source is presented and future perspectives are presented.

THPS102

Novel Schemes for the Narrow Band Sparc THz Source using a Comb like e-beam

linac, radiation, cavity, laser

3672

B. Marchetti
INFN-Roma II, Roma, Italy
M. Boscolo, M. Castellano, E. Chiadroni, M. Ferrario, B. Spataro, C. Vaccarezza
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
C. Ronsivalle
ENEA C.R. Frascati, Frascati (Roma), Italy

The development of radiation sources in the THz spectral region has become more and more interesting because of the peculiar characteristics of this radiation: it is non ionizing, it penetrates dielectrics, it is highly absorbed by polar liquids, highly reflected by metals and reveals specific "fingerprint" absorption spectra arising from fundamentals physical processes. The THz source at SPARC is an accelerator based source for research investigations (e.g. material science, biology fields). By means of e-beam manipulation technique, a longitudinal modulated beam, the so-called comb beam, can be produced at Sparc. In terms of THz sources, such e-beam distribution allows to produce high intensitiy narrow band THz radiation, whose spectrum strongly depends on the charge distribution inside the e-beam. Different linac schemes are compared. In particular, spectra obtained using the comb-beam compression through velocity bunching including a IV harmonic RF section is showed.

THPZ014

LHeC Lattice Design

optics, dipole, lattice, insertion

3714

M. Fitterer, O.S. Brüning, H. Burkhardt, B.J. Holzer, J.M. Jowett, K.H. Meß, T. Risselada
CERN, Geneva, Switzerland
M. Klein
The University of Liverpool, Liverpool, United Kingdom
A.-S. Müller
KIT, Karlsruhe, Germany

The Large Hadron Electron Collider (LHeC) aims at lepton-proton and lepton-nucleus collisions with centre of mass energies of 1-2 TeV at ep luminosities in excess of 10³3 cm^-2 s^-1. We present here a lattice design for the electron ring option, which meets the design parameters and also the constraints imposed by the integration of the new electron ring in the LHC tunnel.

THPZ015

Synchrotron Radiation in the Interaction Region for a Ring-Ring and Linac-Ring LHeC

radiation, linac, interaction-region, luminosity

3717

N.R. Bernard
UCLA, Los Angeles, California, USA
R. Appleby, L.N.S. Thompson
UMAN, Manchester, United Kingdom
N.R. Bernard
ETH, Zurich, Switzerland
B.J. Holzer, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland
M. Klein
The University of Liverpool, Liverpool, United Kingdom
P. Kostka
DESY Zeuthen, Zeuthen, Germany
B. Nagorny, U. Schneekloth
DESY, Hamburg, Germany

The Large Hadron electron Collider (LHeC) aims at bringing hadron-lepton collisions to CERN with center of mass energies in the TeV scale. The LHeC will utilize the existing LHC storage ring with the addition of a 60 GeV electron accelerator. The electron beam will be stored and accelerated in either a storage ring in the LHC tunnel (Ring-Ring) or a linac tangent to the LHC tunnel (Linac-Ring). Synchrotron Radiation (SR) in the Interaction Region (IR) of this machine requires an iterative design process in which luminosity is optimized while the SR is minimized. This process also requires attention to be given to the detector as the beam pipe must be designed such that damaging effects, such as out-gasing, are minimized while the tracking remains close to the IP. The machinery of GEANT4 has been used to simulate the SR load in the IR and also to design absorbers/masks to shield SR from backscattering into the detector or propagating with the electron beam. The outcome of these simulations, as well as cross checks, are described in the accompanying poster which characterizes the current status of the IR design for both the Ring-Ring and Linac-Ring options of the LHeC in terms of SR.

THPZ016

Interaction Region Design for a Ring-Ring LHeC

quadrupole, optics, luminosity, proton

3720

L.N.S. Thompson, R. Appleby
UMAN, Manchester, United Kingdom
N.R. Bernard
UCLA, Los Angeles, California, USA
M. Fitterer
KIT, Karlsruhe, Germany
B.J. Holzer
CERN, Geneva, Switzerland
M. Klein
The University of Liverpool, Liverpool, United Kingdom
P. Kostka
DESY Zeuthen, Zeuthen, Germany
L.N.S. Thompson
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The Large Hadron Electron Collider project is a proposal to study e-p and e-A interactions at the LHC. Using one of the LHC's proton beams, an electron beam of relatively low energy and moderately high intensity provides high luminosity TeV-scale e-p collisions at one of the LHC interaction points, running simultaneously with existing experiments. Two designs are studied; an electron ring situated in the LHC tunnel, and an electron linac. The focus of this paper is on the ring design. Designing an e-p machine presents interesting accelerator physics and design challenges, particularly when considering the interaction region. These include coupled optics, beam separation and unconventional mini-beta focusing schemes. Designs are constrained by an array of interdependent factors, including beam-beam interaction, detector dimensions and acceptance, luminosity and synchrotron radiation. Methods of addressing these complex issues are discussed. The current designs for the LHeC Ring-Ring interaction region and long straight section are presented and discussed, in the context of the project goals and design challenges encountered. Future developments and work are also discussed.

THPZ017

Achromatic Low-beta Interaction Region Design for an Electron-ion Collider

ion, sextupole, betatron, interaction-region

3723

V.S. Morozov, Y.S. Derbenev
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Supported in part by Muons, Inc.
An achromatic Interaction Region (IR) design concept is presented with an emphasis on its application at an electron-ion collider. A specially-designed symmetric Chromaticity Compensation Block (CCB) induces an angle spread in the passing beam such that it cancels the chromatic kick of the final focusing quadrupoles. Two such CCB’s placed symmetrically around an interaction point (IP) allow simultaneous compensation of the 1st-order chromaticities and chromatic beam smear at the IP without inducing significant 2nd-order aberrations. Special attention is paid to the difference in the electron and ion IR design requirements. We discuss geometric matching of the electron and ion IR footprints. We investigate limitations on the momentum acceptance in this IR design.

THPZ019

High Luminosity Electron-hadron Collider eRHIC

hadron, linac, luminosity, proton

3726

V. Ptitsyn, E.C. Aschenauer, J. Beebe-Wang, S.A. Belomestnykh, I. Ben-Zvi, R. Calaga, X. Chang, A.V. Fedotov, H. Hahn, L.R. Hammons, Y. Hao, P. He, A.K. Jain, E.C. Johnson, D. Kayran, J. Kewisch, V. Litvinenko, G.J. Mahler, W. Meng, B. Parker, A.I. Pikin, T. Rao, T. Roser, B. Sheehy, J. Skaritka, R. Than, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, G. Wang, Q. Wu, W. Xu
BNL, Upton, Long Island, New York, USA

We present the design of a future high-energy high-luminosity electron-hadron collider at RHIC called eRHIC. We plan adding 20 (30) GeV energy recovery linacs to accelerate and to collide polarized and unpolarized electrons with hadrons in RHIC. The center-of-mass energy of eRHIC will range from 30 to 200 GeV. The luminosity exceeding 10³4 cm^-2s⁻¹ can be achieved in eRHIC using the low-beta interaction region which a 10 mrad crab crossing. A natural staging scenario of step-by-step increases of the electron beam energy by builiding-up of eRHIC's SRF linacs. We report on the eRHIC design and cost estimates for it stages. We discuss the progress of eRHC R&D projects from the polarized electron source to the coherent electron cooling.

THPZ020

eRHIC Interaction Region Design

ion, proton, lattice, interaction-region

3729

D. Trbojevic, J. Beebe-Wang, Y. Hao, D. Kayran, Y. Luo, V. Ptitsyn, N. Tsoupas
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: *Work performed under a Contract Number DE-AC02-98CH10886 with the auspices of the US Department of Energy.
Interaction region design of the future electron ion collider at Relativistic Heavy Ion Collider (eRHIC) is presented. Polarized protons/Helium and heavy ions will collider with 5-30 GeV polarized electrons with a 10 mrad angle by using the crab cavity crossing. The interaction region is designed without bending electrons to avoid problems with synchrotron radiation. Use of the combined function magnet in the ion side allows detection of neutrons. Design allows detection of deep virtual scattering as well as detection of partons with lower energies (po/2.5). The betatron function at collisions is 5 cm assuming use of three dimensional electron beam cooling. Special chromaticity correction is applied in both sides of the ion straight section interaction region. Electrons arrive with avoiding completely synchrotron radiation at the detector. Special superconducting combined function magnet is designed to allow passage of electrons through the field free region.

THPZ024

Updated Design of the Italian SuperB Factory Injection System

injection, linac, positron, emittance

3738

S. Guiducci, M.E. Biagini, R. Boni, M.A. Preger, P. Raimondi
INFN/LNF, Frascati (Roma), Italy
J. Brossard, O. Dadoun, P. Lepercq, C. Rimbault, A. Variola
LAL, Orsay, France
A. Chancé
CEA, Gif-sur-Yvette, France
J.T. Seeman
SLAC, Menlo Park, California, USA

The ultra high luminosity B-factory (SuperB) project of INFN requires a high performance and reliable injection system, providing electrons at 4 GeV and positrons at 7 GeV, to fulfill the very tight requirements of the collider. Due to the short beam lifetime, continuous injection of electrons and positrons in both HER and LER rings is necessary to keep the average luminosity at a high level. An updated version of the injection system, optimized at higher repetition frequency is presented. This scheme includes a polarized electron gun, a positron production scheme with electron/positron conversion at low energy 0.6 GeV, and a 1 GeV damping ring to reduce the injected emittance of the positron beam.

FRXAA01

Theory of Microwave Instability and Coherent Synchrotron Radiation in Electron Storage Rings

impedance, synchrotron, shielding, storage-ring

3774

Y. Cai
SLAC, Menlo Park, California, USA

Funding: This work was supported by Department of Energy Contract No. DE-AC02-76SF00515.
Bursting of coherent synchrotron radiation has been observed and in fact used to generate THz radiation in many electron storage rings. In order to understand and control the bursting, we return to the study of the microwave instability. In this talk, we will report on the theoretical understanding, including recent developments, of the microwave instability in electron storage rings. The historical progress of the theories will be surveyed, starting from the dispersion relation of coasting beams, to the work of Sacherer on a bunched beam, and ending with the Oide and Yokoya method of discretization. This theoretical survey will be supplemented with key experimental results over the years. Finally, we will describe the recent theoretical development of utilizing the Laguerre polynomials in the presence of potential-well distortion. This self-consistent method will be applied to study the microwave instability driven by commonly known impedances, including that of coherent synchrotron radiation.

Slides FRXAA01 [0.948 MB]