CLS, Saskatoon, Saskatchewan
Funding: CLS supports the upgrade of the 250 MeV linac.
The Canadian Light Source (CLS) 250 MeV linac, originally constructed in the 1960's, serves as the injector for the 2.9 GeV synchrotron radiation facility[1] located on the University of Saskatchewan campus. The linac has operated reasonably well for routine operation of the light source. However, the long-term goal of operating the CLS storage ring in top-up mode will place increased demands on the linac for stability and availability that cannot be met with the existing system. Consequently, an upgrade is planned over the next two years to get higher beam stability, reliability and reproducibility. In this paper, the existing linac system will be described and the planned upgrade will be reported.
TRIUMF, Vancouver
Victoria University, Victoria, B.C.
TRIUMF, in collaboration with university partners, proposes to construct a megawatt-class electron linear accelerator (e-linac) as a driver for U(γ,f) of actinide targets for nuclear astrophysics studies, and 9Be(γ,p)8Li for beta-NMR materials science. The e-linac is part of a broader proposal for an expansion of the TRIUMF rare isotope beams capability through a new facility to be named ARIEL. The e-linac design and prospects for funding are elaborated.
CEA, Bruyeres-le-Chatel
The design of a 15 MeV, 2 kA peak current, electron accelerator for the DEINOS project is presented. It is dedicated to a new radiographic facility. The accelerator design is based on a dc photo-injector and a rf superconducting linac. Up to twenty electron micro-pulses, 100 ps time duration and 200 nC bench charge are emitted at 352 MHz repetition rate from a CS2Te photocathode and accelerated to 2.5 MeV in the dc diode before injection into a superconducting linac. A general description of the main accelerator components and the beam dynamics simulations are presented.
CEA, Gif-sur-Yvette
CERN, Geneva
LAL, Orsay
The CLIC project based on the innovative Two Beams Acceleration concept is currently under study at CTF3 where the acceleration of a probe beam will be demonstrated. This paper will describe in details the status of the probe beam linac called CALIFES. This linac (170 MeV, 1 A) is developed by CEA Saclay, LAL Orsay and CERN. It will be installed in the new experimental area of CTF3 to deliver short bunches (1.8 ps) with a charge of 0.6 nC to the CLIC 12 GHz accelerating structures. The linac consists in an rf gun triggered by a laser beam, three LIL sections for bunching and acceleration, a beam diagnostic system and a single klystron with a pulse compression cavity and a dedicated rf network. We report new results of beam dynamic simulation considering the new CLIC parameters. We will give an estimation of the energy and phase deviation over the bunch train (140 ns long) by transient calculation of beam loading. Details about the fabrication of the rf gun, the cavity BPM, the HV modulator and the power phase shifter will be described. New results from laser system studies are discussed. The construction of CALIFES and the start of commissioning will be also reported.
ELSA, Bonn
DESY, Hamburg
Since 1966 a Varian factored injector is in use at the accelerator complex of the University of Bonn serving several experiments to investigate the subnuclear structure of matter. This injector will have to be replaced for several reasons. The new injector will operate in a single bunch mode of 2 A beam current and is currently under construction. Also a 2 μs long pulse mode of 500 mA beam current will be available for ordinary accelerator operation for hadron physics experiments. Produced by a pulsed thermionic 90 kV gun, compression of the pulses is achieved by a 500 MHz prebuncher as well as one β-matching travelling wave buncher running at the linac frequency of 3 GHz. The injector has been designed and optimised using the software package EGUN and numerical simulations based on the paraxial differential equations. The single bunch mode will allow to investigate single bunch instabilities within the Helmholtz alliance "Physics at the Terascale".
TU Darmstadt, Darmstadt
Funding: Work supported by the DFG through SFB 634
After 15 years operating the S-DALINAC the design quality factor for the superconducting cavities has still not been reached. Currently, the cavities are heat treated at 850 C in an UHV furnace installed in Darmstadt three years ago. We will report about the furnace, the heat treatment procedure and the results of subsequent surface resistance measurements. Prior to the heat treatment the field flatness of some of the 20 cell elliptical cavities has been measured, leading to unexpected operational findings to be reported: operating and frequency-tuning the cavity for several years led to heavy distortions of the field flatness. This might be an indication that the frequency tuning of the cavity done by compressing the cavity longitudinally, does not act uniformly on each cell even though the cavity is only supported at the end cells. The paper will close with a status report on machine operation and modifications undertaken during the last two years.
TU Darmstadt, Darmstadt
TEMF, TU Darmstadt, Darmstadt
IKP, Mainz
ANL, Argonne
Funding: Work supported by the DFG through SFB 634
At the superconducting Darmstadt linear accelerator S-DALINAC currently two upgrades of the injector are underway: The current upgrade for the injector mainly involves the superconducting rf part. In order to increase the maximum current from 60 uA to 150 or 250 uA the power coupler design had to be modified, resulting in major changes in the whole cryo-module. Second, an additional polarized electron source (SPIN) has been set-up at an offline test area. There, the polarized electrons are produced by photoemission at a strained GaAs cathode on a 100 kV platform. The test beam line includes a Wien filter for spin manipulation, a Mott polarimeter for polarization measurement and additional diagnostic elements. We will give an overview over the project, report on the status and present first measurement results including the proof of polarisation.
DESY, Hamburg
The Linac II at DESY consists of a 6A/150kV DC electron gun, a 400 MeV primary electron linac, a 800 MW positron converter, and a 450 MeV secondary electron/positron linac. The Particle Intensity Accumulator (PIA) is also considered part of the injector complex accumulating and damping the 50 Hz beam pulses from the linac and transferring them with a rate of 6.25 Hz or 3.125 Hz into the Synchrotron DESY II. The typical positrons rates are 6·1010/s. DESY II and Linac II will serve as injectors for the two synchrotron light facilities PETRA III and DORIS. Since PETRA III will operate in top-up mode, Linac availability of 98-99% are required. DORIS requires positrons for operation. Therefore during top-up mode positrons are required for both rings. In order to maintain its reliability over the operation time of the new facility PETRA III, the major components of the linac were renovated. Some components were redesigned taking into account experience from 30 years of operation.
KEK, Ibaraki
GUAS/AS, Ibaraki
MELCO SC, Tsukuba
IHEP Beijing, Beijing
The 8 GeV Linac at KEK provides electrons and positrons to Photon Factory (PF) and B-Factory (KEKB). Simultaneous top-up injections have been considered for both PF and KEKB rings in order to improve the injection efficiency and the stability. Fast beam-switching mechanisms are being implemented, upgrading the timing and control systems. While the present system provides precise timing signals for 150 devices, many of the signals will be dynamically switched using an event system. A new scheme has been developed and tested to enable double-fold synchronization between rf signals. Fast controls of low-level rf, beam instrumentation, a kicker, a gun, and beam operation parameters will also be upgraded.
KEK, Ibaraki
KEKB injector linac supplies electron and positron beams to the KEKB storage rings and the synchrotron radiation facility rings (PF, AR) as well. Injection modes to these four destinations are switched by inserting and extracting positron generation target, changing magnet parameters and acceleration rf phases. To enable pulse-by-pulse switching in three out of the four modes, a pulse bend and pulse steerings are introduced. For DC quads and DC steerings, compatible beam-optical settings for beams of different beam-energy profiles are introduced. We have been performing beam studies to establish the pulse-by-pulse mode switching for daily beam operation. This paper describes a scheme for the mode switching and reports on an achievement of the beam studies.
KEK, Ibaraki
The KEKB linac continuously injects 8 GeV electron and 3.5 GeV positron beams into the KEKB rings: HER(high energy ring) and LER(low energy ring). The energy spread of the 8-GeV electron beam, which is accelerated to an 1.7 GeV 180-degree arc section and reaccelerated after this arc to a final energy of 8 GeV, is optimized by adjusting rf acceleration phases so as to assure efficient injections. When rf phases are slightly changed or drifted for some reasons, the beam not only shows larger energy spreads but also indicates two clusters on a beam profile monitor located at large energy dispersions. In this connection, a longitudinal beam profile was measured after the arc section with a streak-camera system utilizing an OTR(Optical Transition Radiation) bunch monitor. The observed bunch shape clearly shows a two-microbunch structure, suggesting that it could be generated in the arc section. Various experimental data as well as some CSR-related speculations are presented.
KEK, Ibaraki
KEK injector linac provides an injection beam for four storage rings, KEKB high energy electron ring(HER), low energy positron ring(LER), PF-AR electron ring, and PF electron ring. The injection beams for these rings have different energies and intensities. Recently, a requirement of simultaneous injection among these rings arises to make a top-up injection possible. Magnetic fields of DC magnets to confine the beam to the accelerating structures can not be changed between pulse to pulse, although the beam energy can be controlled by fast rf phase shifters of klystrons. This implies that a common magnetic field of the bending magnets and the quadrupole magnets should be utilized to deliver beams having different characteristics. Therefore, we have designed multi-energy optics for the KEKB-HER electron ring(8 GeV, 1 nC/pulse), the PF electron ring(2.5 GeV, 0.1 nC/pulse), and the KEKB-LER positron ring(3.5 GeV, 0.4 nC/pulse). We present a performance of the multi-energy injector linac.
KEK, Ibaraki
The KEK electron/ positron linac is a 600 m long linear accelerator with the maximum energy 8 GeV electron and 3.5 GeV positron, and it is used as an injector for 4-rings (KEKB e-/ e+, PF, PF-AR). To increase the operation efficiency, we have an injector upgrade plan for a simultaneous injection operation. In this paper, we will present the operation scheme and the progress of upgrade project.
IHEP Beijing, Beijing
After the major upgrade in 2005, the BEPC injector linac has been commissioning and working smoothly for more than two years. A 2.1 GeV, 66 mA positron beam at the linac end has been obtained, and the highest injection rate into the ring of 80 mA/min. at 50 pps is reached, much higher than the design goal of 50 mA/min. The machine is working stable, the mal function was about 2% in the past two years, including the system test and the commissioning.
CERN, Geneva
An automatic beam steering application for CTF 3 is being designed in order to automatize operation of the machine, as well as providing a test-bed for advanced steering algorithms for CLIC. Beam-based correction including dispersion free steering have been investigated. An approach based on a PLACET on-line model has been tested. This paper gives an overview of the current status and the achieved results of the CTF3 automatic steering.
CERN, Geneva
The CERN CLIC test facility (CTF3) aims at assessing the feasibility of the future multi-TeV Compact Linear Collider (CLIC). The CTF3 Tail Clipper Collimator (TCC) will serve to adjust the bunch train length of the beam extracted from the combiner ring, in combination with a fast kicker magnet. In addition, the TCC will operate, when required, as an internal beam dump. The challenge of the TCC design is to meet the requirements of both collimator and dump operational modes for a low energy e- beam (100-300 MeV) of 35 A peak intensity. The TCC collimator will be installed at the end of 2008 in the TL2 transfer line of CTF3. This paper describes the final design of the TCC and the main issues related to its integration in the line.
NSC/KIPT, Kharkov
Funding: The present work is supported by the STCU project #P233
The accelerator driven subcritical assembly facility is under development in the National Science Center Kharkov Institute of Physics and Technology. The important component of the facility is an electron linac with energy of particles of 100-200 MeV and average beam current of 1 mA. In this paper we focus on the S-band electron linac design. The accelerator scheme includes the injector based on evanescence waves, rf chopper, five accelerating structures and energy compression system. The results of calculation of accelerating structure performances and linac systems are considered in the paper
NSC/KIPT, Kharkov
The results of beam dynamic simulation in an S-band injector that can be used for creation of the powerful electron linac are presented in the report. The injector consists of a diode electron gun with beam current of up to 2 A at energy of electrons of 25 keV, the klystron type prebuncher and the three cavity buncher. In the buncher, due to the special choice of eigen frequencies of resonators, maximal amplitude of the field on the axis of resonators exponentially increase from the first (downstream of the beam) resonator to the last resonator. It allows effective bunching the intensive electron beam and accelerating it to relativistic velocities. For providing of low transversal beam emittance the injector is placed in the external magnetic field. The injector provides more than 1 A of beam current at particle energies of about 1 MeV. Attention is paid to research of transients and stability of injector work.
SAIC, Los Alamos, New Mexico
LANL, Los Alamos, New Mexico
LLNL, Livermore, California
NSTec, Los Alamos, New Mexico
Voss Scientific, Albuquerque, New Mexico
The DARHT-II accelerator produced a 2 kA, 17 MeV beam over a 1600 ns flattop. After exiting the accelerator, the long pulse is sliced into four short pulses by a kicker and quadrupole septum and then transported and focused on a target for conversion to bremsstrahlung for radiography. We describe the initial commissioning tests of the kicker, septum, transport, and multi-pulse converter target. The results of beam measurements made during the commissioning of the accelerator downstream transport are described. Beam optics simulations of the commissioning results are described.
SLAC, Menlo Park, California
Funding: US DOE
This paper reports the design and test results on novel topology, high-efficiency, and low operating temperature, 1,320-watt power modules for high availability power supplies. The modules permit parallel operation for N+1 redundancy with hot swap capability. An embedded DSP provides intelligent start-up and shutdown, output regulation, general control and fault detection. PWM modules in the DSP drive the FET switches at 20 to 100 kHz. The DSP also ensures current sharing between modules, synchronized switching, and soft start up for hot swapping. The module voltage and current have dedicated ADCs (>200 kS/sec) to provide pulse-by-pulse output control. A Dual CAN bus interface provides for low cost redundant control paths. Over-rated module components provide high reliability and high efficiency at full load. Low on-resistance FETs replace conventional diodes in the buck regulator. Saturable inductors limit the FET reverse diode current during switching. The modules operate in a two-quadrant mode, allowing bipolar output from complimentary module groups. Controllable, low resistance FETs at the input and output provide fault isolation and allow module hot swapping.
BESSY GmbH, Berlin
Funding: Work partially funded by the European Commission in the Sixth Framework Program, contract no. 011935 EUROFEL-DS5, BMBF and Land Berlin.
Most concepts for next generation light sources base on linear accelerators (linac) due to their excellent beam properties. In case of high electron energies and extreme average currents Energy Recovery Linacs (ERL) are mandatory. In this paper we investigate the rf field stability in a generic superconducting, cw operated ERL. By using rf control cavity simulations and longitudinal beam dynamics the influence of rf field stability on the energy recovery process is analyzed. Since the ERL aims for a small net beam loading cavities are operated at a high loaded quality factor. Therefore they are operated at a low bandwidth and are very susceptible to microphonics detuning. We considered the field stability under the influence of limited rf power, mechanical cavity detuning, varying beamloading, synchronization deviations and varying bunch parameters at injection into the linac. The resulting temporal and energy jitter at the linac end will be transformed in the return arc and leads to rf phase deviations on the return path. Implications of varying beam loading on the ERL performance are examined.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An Energy Recovery Linac (ERL) is one possibility for an upgrade to the Advanced Photon Source (APS). In addition to the linac itself, our concept involves a large turn-around arc (TAA) at 7 GeV that would eventually accommodate many new beamlines. Previously, we based the TAA design on isochronous triple-bend archromat (TBA) cells, since these are expected to provide some immunity to the effects of coherent synchrotron radiation. In the present work, we compare the previous TBA-based design to a new design based on double-bend achromat cells, in terms of emittance growth, energy spread growth, and energy recovery. We also explore the trade-off between optimization of the beta functions in the straight sections and minimization of emittance growth.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An Energy Recovery Linac (ERL) is one possibility for an upgrade to the Advanced Photon Source (APS). Such a system involves not only a long linac, but also long transport lines with many dipole magnets. Since the bunches are short, we may expect that coherent synchrotron radiation and longitudial space charge will have an affect on the beam dynamics. Although previous studies have shown minimal effects for an initially quiet beam distribution, the possibility of a microbunching instability seeded by initial density modulation must be evaluated. We present and discuss simulation results showing the growth of density modulations in two possible lattices for an ERL upgrade of the APS.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
One of the possible options for the Advanced Photon Source (APS) upgrade is an energy-recovery linac (ERL). In its main operating mode, the ERL bunch length would be two picoseconds. Even though this bunch length is already a factor of 20 shorter than the present APS bunch length, some experiments might require shorter X-ray pulses. For the APS storage ring, we plan to use an rf deflection technique* to generate one-picosecond X-ray pulses. In this approach, an rf cavity is used to deliver longitudinally dependent vertical kick to the electron beam and then a pair of slits is used to slice vertically streaked X-ray beam. We investigate the possibility and benefits of utilizing this technique to generate shorter X-ray pulses at the ERL.
*A. Zholents, et al., Nucl. Instr. and Meth. A 425 (1999) 385.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An energy recovery linac (ERL) is one of the candidates for an upgrade of the Advanced Photon Source (APS). In addition to the APS ring and full-energy linac, our design also includes a large turn-around arc that could accommodate new X-ray beamlines as well. In total, the beam trajectory length would be close to 3 km. The ERL lattice has a strong focusing to limit emittance growth, and it includes strong sextupoles to keep beam energy spread under control and minimize beam losses. As in storage rings, trajectory errors in sextupoles will result in lattice perturbations that would affect delivered X-ray beam properties. In storage rings, the response matrix fit method is widely used to measure and correct linear lattice errors. Here, we explore the application of the method to the linear lattice correction of ERL.
BNL, Upton, Long Island, New York
AES, Medford, NY
JLAB, Newport News, Virginia
Funding: Work performed under contract No. DE-AC02-98CH10886 with the auspices of the DoE of United States.
An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under construction at Brookhaven National Laboratory (BNL) for testing concepts for high-energy electron cooling and electron-ion colliders. One of the goals is to demonstrate an electron beam with high charge per bunch (~5 nC) and extremely low normalized emittance (~5 mm-mrad) at an energy of 20 MeV. Flexible lattice of ERL loop provides a test-bed for testing issues of transverse and longitudinal instabilities and diagnostics of intense cw e-beam. The superconducting 703 MHz rf photoinjector is considered as an electron source for such a facility. At first we develop the straight pass (gun – 5 cell cavity – beam stop) test for the SRF Gun performance studies. Then the novel injection line concept of emittance preservation at the lower energy will be tested at this ERL. In this paper we present the status and our plans for construction and commissioning of this facility.
Osaka Prefecture University, Sakai
The coherent synchrotron and transition radiation from electron bunches of a linear accelerator (linac) has continuous spectra in a submillimeter to millimeter wavelength range at relatively high peak-intensities. This light source has been applied to absorption spectroscopy by the authors for various kinds of matters with relatively strong light absorbance such as water and aqueous solutions. The other important characteristics of the coherent radiation are picosecond pulsed light and the high peak intensity of the electric field which can be introduced into matters. In our new project the light source using the pulsed coherent synchrotron and transition radiation will be developed by using the electron beams of a 18 MeV S-band electron linac at Osaka Prefecture University (OPU). The pulse shape of the radiation has been evaluated from the shape of the electron bunch. The system of the light source has been optimized and is under construction. The light source will be applied to the pulsed excitation of matters and to the pump-probe experiment using the electron beam and the coherent radiation.
Diamond, Oxfordshire
Several modifications have been made to the 100 MeV Diamond Light Source pre-injector linac since initial commissioning in 2005 to improve beam stability and reliability and to increase the scope of operation of the system. Stability enhancements include tighter thermal control of low-level rf electronics, and a modified timing system for gun and linac operation. The linac has been optimised for multibunch filling of the storage ring and for single-bunch top-up operation with gun charge and timing determined by the state of the storage ring fill. Low-energy beam generation has been studied for fault-mode operation using one of the two rf stations, and a study of the options available for Diamond based on routine operation in this mode has been carried out. A summary of operational experience is presented, together with options for future development
Diamond, Oxfordshire
A New Light Source project has been initiated to deliver a conceptual design for a next-generation light source facility in the UK. One option for such a light source is a free electron laser based on normal-conducting linac technology. This paper considers the different options available for waveband, gun and rf design of a normal-conducting linac FEL, and presents an overview of accelerating structure, modulator and klystron capability and availability. Particular attention is paid to the issue of the operation of a normal-conducting device at repetition rates of several hundred pulses per second. Overall capabilities and limitations of this approach are illustrated by reference to a start-to-end model of a suitable 3 GeV S-band linac design.
DESY, Hamburg
In order to compensate nonlinear distortions of the longitudinal phase space a rf section operated at three times the 1.3 GHz frequency of the existing TTF cavities is foreseen in the next phase of FLASH. Four modules of a nine-cell 3.9 GHz cavities will be installed right after the first accelerating module ACC1. These cavities could cause additional long-range wake fields which would affect the multi bunch (mb) beam dynamics leading to increase of the mb emittance. The mb emittance at the end of the linac is determined by the strength of the transverse wake fields in the rf system. These higher order modes appear after any off-crest moving bunch, which could happen either due to the cavity misalignment, or by transverse position fluctuations of the injected bunches. It is intended to damp them by means of the HOM couplers, which may reduce the damping time by factor of 105. The misalignment of the cavities offsets is expected to be by 0.5 mm rms. The paper describes the results of the simulations on the dependence of the mb emittance on cavities misalignment offsets and damping strength of the HOM couplers in the planned 3.9 GHz rf section.
DESY, Hamburg
The XFEL injector building has a length of 74.3 metres and is divided by 2.5 m long concrete shielding wall. The section upstream the shielding wall will have a length of 42.3 m and give place for the gun, accelerating module, 3rd harmonic section, laser heater and the beam diagnostics section. At its end the possibility for the beam dump is foreseen so that the tuning of the beam in the injector would become possible without any impact on the subsequent parts of the XFEL. Each of these components sets certain requirements on beam optics which may compete with each other. Downstream the shielding the beam will be vertically displaced by 2.75 m over the distance of 20 m by means of the so called dogleg - a combination of two four cell arcs (8 cell system). Since the vertical displacement takes place there it is important to optimize cells in such an order that the chromatic effects don't impact the beam quality noticeably. In this paper we describe the solution for the beam optics at the XFEL injector.
DESY, Hamburg
INFN/LASA, Segrate (MI)
Fermilab, Batavia
Ultra short bunches with high peak current are required for the creation of high brilliance coherent light in the VUV and X-ray range in undulators. At the Free Electron Laser in Hamburg (FLASH) and the European X-ray free electron laser (XFEL) they are obtained by a two stage bunch compression scheme based on acceleration off the rf field crest and transverse magnetic chicanes. The deviation of the rf field's sine shape from a straight line leads to long bunch tails and reduces the peak current. This effect can be eliminated by adding a third harmonic rf system. The paper gives an overview on the actual status of the beam dynamical examinations and as well on the development of the third harmonic sub-systems like modules, cavities and radio frequency systems for FLASH and the XFEL.
DESY Zeuthen, Zeuthen
INRNE, Sofia
DESY, Hamburg
YerPhI, Yerevan
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
INFN/LASA, Segrate (MI)
BESSY GmbH, Berlin
Uni HH, Hamburg
MEPhI, Moscow
Funding: This work was partly supported by the European Community, contracts RII3-CT-2004-506008 and 011935, and by the 'Impuls- und Vernetzungsfonds' of the Helmholtz Association, contract number VH-FZ-005.
The Photo Injector Test facility at DESY, Zeuthen site, (PITZ) was built to develop and optimize high brightness electron sources for Free Electron Lasers (FELs) like FLASH and the European XFEL. In the last shutdown a new RF gun cavity with improved water cooling was installed and conditioned. It is the first rf gun where the surface cleaning was done with dry ice technique instead of high pressure water rinsing and it showed a 10 times lower dark current emission than its precursor gun, even at cathode gradients as high as 60M V/m. In addition, a new photo cathode laser system was installed and will be available for operation in spring 2008. It will allow flat-top temporal laser shapes with 2ps rise/fall time. According to beam dynamics simulations this will further improve the beam quality reported at earlier conferences* and will lead to unprecedented low transverse projected emittance beams at a charge level of 1nC. This contribution will summarize the experimental results from the summer 2008 running period covering transverse projected emittance optimization, thermal emittance from the photocathode, longitudinal phase space and first transverse slice emittance measurements.
* L. Staykov et al., "Measurements of the Projected Normalized Transverse Emittance at PITZ", Proceedings of the FEL 2007, Novosibirsk, Russia, August 2007.
Kyoto IAE, Kyoto
An MIR-FEL facility, Kyoto University FEL (KU-FEL), has been developed for applications in "sustainable energy science", such as fundamental studies on high-efficiency solar cells. The KU-FEL, consisting of an S-band thermionic rf gun, a 3 m accelerator tube and a planer undulator, aims to generate 4-13 μmeter tunable FEL. The first lasing was achieved on March, 2008 at 12.4 μmeters by using a beamloading compensation method both in the rf gun and in the accelerator tube. *Furthermore, we introduced detuning to the rf gun and succeeded to generate an electron beam with macropulse duration of 5.1 μseconds, average current of 100 mA and energy spread of 0.5% which led to power saturation in FEL. In the conference, the improvements of the electron beam properties and power saturation of the KU-FEL will be discussed.
*H. Ohgaki et al., 'First Lasing at 12 um Mid Infrared Free Electron Laser at Kyoto University', Japanese Journal of Applied Physics, accepted for publication. (2008).
JINR, Dubna, Moscow Region
JINR/LHE, Moscow
800 MeV electron linac (LINAC-800) is under construction at JINR. It will be used as a driver for Volume FEL and as a test bench for commissioning of elements of the ILC. Presently the electron injector is commissioned and the electron beam of 50 keV of the energy at current of about 15 mA was obtained. The results of the injector operation at nominal parameters (400 keV, 300 mA) and commissioning of the first accelerating section at 20 MeV are discussed.
PSI, Villigen
In the planned PSI-XFEL facility, three FEL branches will supply coherent, ultra-bright, and ultra-short XFEL photons at wide wavelength range. FEL branch 1 will use a 6.0 GeV driving linac to generate hard X-rays from 0.1 nm to 0.3 nm, while FEL branch 2 is foreseen for X-rays from 0.3 nm to 1.0 nm. However, FEL branch 3 was designed to supply spatially as well as temporally coherent soft X-rays from 1.0 nm to 10 nm with the High-order Harmonic Generation based seeded HGHG scheme. To reach emittances of 0.2 mm.mrad and to squeeze consequently the whole facility within an 800 m long tunnel, PSI is presently developing an advanced low emittance gun (LEG) based on a 1 MV high gradient pulsed diode and field emission. The advanced LEG will be used to drive FEL branch 1 and 2, while an RF photoinjector will be used to drive the FEL branch 3. In this paper, we describe a CTF3 RF gun based injector, two bunch compressors, two diagnostic sections, and linacs for the PSI-XFEL FEL branch 3.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The UK's new light source project was officially launched on April 11th 2007, which will be based on advanced conventional and free electron lasers, with unique and world leading capabilities. User consulation exercises have already been initiated to determine the fundamental photon output requirements for such a machine. In order to match a nominal requirement for high repetition rates (extending up to 1 MHz), a series of superconducting rf (SRF) linac options have been investigated, reflecting varied beam loading conditions and subsequent high and low power rf solutions.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Several laboratories concentrate their efforts on development of high repetition rate FEL based next generation light sources. One particular concept under development at STFC Daresbury Laboratory specifies high brightness electron bunches with a charge of 0.2-1 nC which arrive with a frequency up to 1 MHz. As emittance of the bunches should not exceed 1 um, traditional high repetition rate thermionic injectors, similar to the ones used at high micropulse repetition rate FELs like ELBE or FELIX, may not be used. We consider three options of high repetition rate injectors based on photocathode guns - a high voltage dc gun, a one and half cell superconducting rf gun and a normal conducting VHF gun, recently proposed at LBNL. We consider practical injector schemes for all three guns and provide the results of beam dynamic simulations. We also discuss the photocathodes which may be used in each gun, as this critical component defines achievable beam parameters and operational efficiency of the injectors.
ANL, Argonne
SLAC, Menlo Park, California
Funding: Work Argonne supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357.
A Beam-Loss Monitor (BLM) system based on the detection of Cerenkov radiation is in development at the Advanced Photon Source (APS) for the Linac Coherent Light Source (LCLS) free-electron laser. The electron beam will vary in energy nominally from 4 to 14 GeV with a beam charge of 0.2 to 1.0 nC and a maximum repetition rate of 120 Hz. To limit radiation-induced demagnetization of the undulator permanent magnets, the BLM will provide beam-loss threshold detection as part of the Machine Protection System (MPS). The detector incorporates a large volume (30 cc) fused silica Cerenkov radiator coupled to a photomultiplier tube (PMT). The output of the PMT is conditioned locally by a charge amplifier circuit and then digitized at the front end of the MPS rack electronics. During commissioning, the device will be calibrated by inserting a 1-micron aluminum foil into the beam, upstream of the undulator magnets. The present design calls for five BLM detector units to be distributed throughout the 33 undulator magnets. Beam-based testing is to begin at the APS storage ring during the summer of 2008. Details and status of the detector hardware, electronics, and simulations will be discussed.
NPS, Monterey, California
Niowave, Inc., Lansing, Michigan
MIT, Middleton, Massachusetts
Stanford University, Stanford, Califormia
Funding: This research is supported by the Office of Naval Research and the Joint Technology Office.
The Naval Postgraduate School (NPS) has begun the design and assembly of the NPS Free-Electron Laser (NPS-FEL). As part of this effort, the original dc gun-based injector system is being refurbished and upgraded. As described in the accompanying paper 'Status of the NPS-FEL' (these Proceedings), the overall NPS-FEL design parameters are for 40 MeV beam energy, 1 nC bunch charge, and 1 mA average beam current, in an energy-recovery linac configuration. As we move towards this configuration, the injector system will be incrementally upgraded to add photocathode capability, have a higher final beam energy, and improve the beam brightness, to meet the demands of the overall experimental program. This paper describes the current status of the injector system, the initial set of experiments planned, and the projected upgrade path.
Fermilab, Batavia
Funding: Work supported by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. DOE and by Northern Illinois University under Contract No. DE-FG02-08ER41532 with the U.S. DOE
We demonstrate analytically and via numerical simulation, how a longitudinal-to-transverse phase space manipulation* can be used to produce a train of femtosecond electron bunches. The technique uses an incoming transversely-modulated electron beam obtained via destructive (e.g. using a multislits mask) or non destructive (e.g. transversely shaping the photocathode drive laser) methods. A transverse-to-longitudinal exchanger insertion is used to map this transverse modulation into a temporal modulation. Limitation of the proposed method and scalability to the femtosecond regime are analysed analytically and with the help of numerical simulation. Application of the method to generation of super-radiant far infrared (and shorter wavelength) radiation in an FEL is explored. Finally, a proof-of-principle experiment is discussed in the context of the Fermilab's A0 photoinjector.
*P. Emma, Z. Huang, K.-J. Kim, and P. Piot, Phys. Rev. ST Accel. Beams 9, 100702 (2006).
LBNL, Berkeley, California
UCB, Berkeley, California
Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The design of the linac delivering the electron bunches into ten independent soft x-ray free electron lasers (FELs) is presented. The bunch repetition rate in the linac is 1 MHz and the bunch repetition rate in each FEL beam line is 100 kHz. Various issues regarding machine layout and lattice, bunch compression, collimation, and the beam switch yard are discussed. Particular attention is given to collective effects. A demanding goal is to preserve both a low beam slice emittance and low slice energy spread during acceleration, bunch compression and distribution of the electron bunches into the array of FEL beamlines. Detailed studies of the effect of the electron beam microbunching resulting from longitudinal space-charge forces and coherent synchrotron radiation as the beam undergoes compression have been carried out and are presented.
LANL, Los Alamos, New Mexico
Particle beams have exhibited a two-stream instability for many decades; this undesirable trait has been well-understood for many years. We propose creating a scheme that uses a beam of electrons with two distinct energies that will develop the two-stream instability as a bunching mechanism. By controlling the beam parameters and seeding them with a low-level rf signal, a gain as high as 2.5 dB per centimeter is predicted. We show the theory behind this concept and recent progress in a developing experiment.
SLAC, Menlo Park, California
The beam stability for the Linac Coherent Light Source (LCLS) Free-Electron Laser (FEL) at Stanford Linear Accelerator Center (SLAC) are critical for X-Ray power, pointing, and timing stability. Studies of the transverse, longitudinal, and intensity stability of the electron beam are presented. Identifying these sources by different methods like correlations, frequency spectrum analysis and other methods is critical for finally eliminating or reducing them.
SLAC, Menlo Park, California
UW-Madison/SRC, Madison, Wisconsin
Funding: The work of AWC and JW was supported by the US Department of Energy under contract DE-AC02-76SF00515. The work of JB was supported by National Science Foundation Award No. DMR-0537588.
A single-pass high-gain X-ray free electron laser (FEL) calls for a high quality electron bunch. In particular, for a seeded FEL, and for a cascaded harmonic generation (HG) FEL, the electron bunch initial energy profile uniformity is crucial to preserve an FEL narrow bandwidth. After the acceleration, compression, and transport, the electron bunch energy profile entering the undulator can acquire temporal non-uniformity. During the cascading stages, the electron bunch energy profile is also not uniform temporally entering the next stage. We study the effects of the electron bunch initial energy profile on the FEL performance, cascaded HG FEL or single stage FEL amplifier. Concrete examples are discussed for seeded FEL projects being studied.
SLAC, Menlo Park, California
UW-Madison/SRC, Madison, Wisconsin
Funding: The work of PE and JW was supported by the US Department of Energy under contract DE-AC02-76SF00515. The work of RAB and KJK was supported by National Science Foundation Award No. DMR-0537588.
For electron bunches driving a hard X-ray free electron laser, the electron bunch high qualities should be preserved as well as possible in the acceleration and compression. For typical configuration, the electron bunch is accelerated in rf cavity and compressed in magnetic chicane. Besides the rf curvature and high-order optics terms in a chicane, the collective effects during the bunch acceleration, transportation, and compression can further distort the phase space and even lead to instability. Among these collective effects, the coherent edge radiation dominates and governs the overall bunch property; while the longitudinal space charge is the main cause for microbunching instability. Random jitter couples to the wakefields and affect the final bunch properties. We study these effects and discuss their implication to general linac design and optimization.
SLAC, Menlo Park, California
Static magnetic field undulators are capable of producing quasi-monochromatic synchrotron radiation of very high brightness. However, it is not possible to quickly change the properties such as polarization of the radiation in a static undulator. It is possible to construct an undulator using microwaves instead of static magnets where the electron beam is undulated by both electric and magnetic fields of an rf wave. A major advantage with a microwave undulator is that the radiation properties can be changed very quickly. The biggest challenge in developing a microwave undulator is in keeping the rf losses low. We are designing a microwave undulator with the aim of achieving at least a tenth of the flux obtained by the BL13 static magnetic field Elliptical Polarized Undulator in the SPEAR ring. We have considered circular waveguide modes and hybrid HE11 mode in a corrugated waveguide as possible candidates for the microwave undulator. It is found that a corrugated waveguide has the lowest rf losses with a very desirable field profile. It is also possible to use this device for a linac driven FEL. Our analysis of the corrugated waveguide cavity for the rf undulator will be presented.
NPS, Monterey, California
Stanford University, Stanford, Califormia
Funding: This research is supported by the Office of Naval Research and the Joint Technology Office.
The Naval Postgraduate School (NPS) has begun the design and assembly of the NPS Free-Electron Laser (NPS-FEL). The basic NPS-FEL design parameters are for 40 MeV beam energy, 1 nC bunch charge, and 1 mA average beam current, in an energy-recovery linac configuration. The NPS-FEL will make use of portions of the Stanford Superconducting Accelerator (decommissioned in 2007), in particular the injector system, Stanford/Rossendorf-style cryomodules and rf system. The injector will be gradually upgraded to improve beam properties and increase the injection voltage. Each cryomodule contains two, 9-cell TESLA-type 1.3 GHz cavities, each cavity powered by an individual 10 kW cw klystron. NPS has committed to refurbishing a building for the FEL, with approximate interior vault dimensions of 7 m x 20 m x 2.5 m. The building has overall dimensions of 12 m x 49 m and will house the vault, control room, and support equipment. This paper describes the overall goals of the program, initial experimental plans, and progress to date.
BNL, Upton, Long Island, New York
The Source Development Laboratory (SDL) at the National Synchrotron Light Source (NSLS) is a laser linac facility dedicated for laser seeded FEL and beam physics R&D. The SDL consists of a RF synchronized Ti:sapphire laser, a BNL photocathode RF gun, a four-magnet chicane bunch compressor, and a 300 MeV linac. To further improve the performance of the laser seeded FEL at the NSLS SDL, we have carried out a systematic experimental characterization of the high-brightness electron beam generated by the photocathode RF gun. We will present the experimental studies of both transverse and longitudinal emittance of electron beam as a function of RF gun phase and solenoid magnet for electron beam charge ranging from 350 pC to 1 nC and their influences on FEL output.
Kyoto ICR, Uji, Kyoto
KEK, Ibaraki
A final focus quadrupole (FFQ) doublet of ILC should have excellent properties such as strong focusing, compactness and less vibrations. In a baseline design, superconducting magnet is supposed to be used, which may have some vibrations traveling through liquid helium. It may not be suitable for FFQ of ILC unless the vibration effect is proven to be negligible. Since the five-disc-singlet proposed by Gluckstern satisfies these properties including continuous adjustability, we are developing a FFQ aiming at a beam test at ATF2. Although the x-y coupling effect is carefully cancelled in the design, fabrication errors or rotation errors may break the cancellation. We are estimating the effect of these errors on the beam size at the interaction point. Two methods are currently carried out. The first one is transfer matrix calculations, which neglects fringing field and higher multipole components. The second one is beam-tracking calculation in measured or calculated magnetic field. The fabricated magnet is under adjustment measuring the magnetic field. The recent results will be presented.
CERN, Geneva
Recently the CLIC study has changed the operating frequency and accelerating gradient of the main linac from 30 GHz and 150 MV/m to 12 GHz and 100 MV/m, respectively. This major change of parameters has been driven by the results from a novel main linac optimization procedure. The procedure allows simultaneous optimization of operating frequency, accelerating gradient, and many other parameters of CLIC main linac. It takes into account both beam dynamics (BD) and high power rf constraints. BD constraints are related to emittance growth due to short- and long-range transverse wakefields. Rf constraints are related to rf breakdown and pulsed surface heating of the accelerating structure. The optimization figure of merit includes the power efficiency, measured as a ratio of luminosity to the input power as well as a quantity proportional to investment cost.
CERN, Geneva
INFN/LNF, Frascati (Roma)
TRIUMF, Vancouver
The objective of the CLIC Test Facility CTF3 is to demonstrate the feasibility issues of the CLIC two-beam technology. CTF3 consists of an electron linac followed by a delay loop, a combiner ring and a two-beam test area. One issue studied in CTF3 is the efficient generation of a very high current drive beam, used in CLIC as the power source to accelerate the main beam to multi-TeV energies. The beam current is first doubled in the delay loop and then multiplied by a factor four in the combiner ring by interleaving bunches using transverse deflecting rf cavities. The combiner ring and the connecting transfer line have been put into operation in 2007. In this paper we give the status of the commissioning, present the results of the combination tests and illustrate in some detail the beam optics measurements, including response matrix analysis, dispersion measurement and applied orbit correction algorithms. We discuss as well the observation of a vertical beam break-up instability which is due to the vertical transverse mode in the horizontal rf deflectors used for beam injection and combination. We outline the attempted methods to mitigate the instability and their effectiveness.
CERN, Geneva
KEK, Ibaraki
SLAC, Menlo Park, California
Demonstration of a gradient of 100 MV/m at a breakdown rate of 10-7 is one of the key feasibility issues of the CLIC project. A high power rf test program both at X-band (SLAC and KEK) and 30 GHz (CERN) is under way to develop accelerating structures reaching this performance. The test program includes the comparison of structures with different rf parameters, with/without wakefield damping waveguides, and different fabrication technologies namely quadrant bars and stacked disks. The design and objectives of the various X-band and 30 GHz structures are presented and their fabrication methods and status is reviewed.
Diversified Technologies, Inc., Bedford, Massachusetts
Funding: U.S. Department of Energy SBIR Program
Diversified Technologies, Inc. (DTI) is developing a driver for a kicker strip-line deflector which inserts and extracts charge bunches to and from the electron and positron damping rings of the International Linear Collider. The kicker driver must drive a 50 Ω terminated TEM deflector blade at 10 kV with 2 ns flat-topped pulses, which according to the ILC pulsing protocol, bursts pulses at a 3 MHz rate within one-millisecond bursts occurring at a 5 Hz rate. The driver must also effectively absorb high-order mode signals emerging from the deflector. In this paper, DTI will describe current progress utilizing a combination of high voltage DSRDs (Drift Step Recovery Diodes) and high voltage MOSFETs. The MOSFET array switch, without the DSRDs, is itself suitable for many accelerator systems with 10 - 100 ns kicker requirements. DTI has designed and demonstrated the key elements of a solid state kicker driver which both meets the ILC requirements, is suitable for a wide range of kicker driver applications. Full scale development and test are exptected to occur in Phase II of this DOE SBIR effort, with a full scale demonstration scheduled in 2009.
KEK, Ibaraki
A new type of rotating anticathode X-ray generator has been developed, in which the electron beam irradiates the inner surface of a U-shaped anticathode. A high-flux electron beam is focused on the inner surface by optimizing the shape of the bending magnet. In order to minimize the sizes of the X-ray source, the electron beam is focused strongly in a short distance by the bending magnet which is small and is close to the rotating anticathode. The power of the electron beam can be increased to the point at which the irradiated part of the inner surface is melted, because a strong centrifugal force fixes the melted part on the inner surface. We have achieved emission of X-rays 10 times more brilliant than can be attained by a conventional rotating anticathode. The development is still in progress. New results will be reported in detail.
Osaka Prefecture University, Sakai
Energetic electron beams higher than several MeV occasionally induce direct nuclear reactions with the target nuclei. These processes are attributed to the quasi-elastic scattering of electrons (e,e') with the target nuclei and similar to the photo-nuclear reactions. These reactions are considered to be useful for the non-destructive analysis of heavy elements such as U and Th. In addition, a two-dimensional analysis is realized only by scanning of electron beam. On the other hand, the huge X-ray burst caused by the bremsstrahlung with the electron pulse bombardment is the most harmful phenomenon for the radiation measurement system. In this study, an ultra low intensity electron beam was used for relieving the problem, which has been developed by modifying an electron linear accelerator. The minimum beam charge about several aC/pulse has been achieved at the present. Consequently, the neutron emitted by Pb(e,e'n)Pb reaction was measured successfully by the use of the low intensity beams. The linearity between the neutron count and the concentration of Pb in the target was verified experimentally.
RISE, Tokyo
KEK, Ibaraki
Kyoto University, Kyoto
Funding: Work supported by a Grant-In-Aid for Creative Scientific Research of JSPS (KAKENHI 17GS0210) and a Grant-In-Aid for JSPS Fellows (19-5789)
A compact and high quality X-ray source is required for various field, such as medical diagnosis, drug manifacturing and biological sciences. Laser-Compton based X-ray source that consist of a compact electron storage ring and a pulsed-laser super-cavity is one of the solutions of a compact X-ray source. Pulsed-laser super-cavity has been developed at Waseda University for a compact high brightness X-ray source. The pulsed-laser super-cavity enables to make high peak power and small waist laser at the collision point with the electron beam. 357 MHz mode-locked Nd:VAN laser pulses can be stacked stably in a 420 mm long Fabry-Perot cavity with "burst mode", which means stacking of electron beam synchronized amplified pulses in our R&D. In view of this successful result, we have started an X-ray generation experiment using a super-cavity and a multi-bunch electron beam at KEK-LUCX. Recently, the demonstration experiment between the burst mode pulsed-laser super-cavity and the 100bunch multi-bunch electron beam is successfully performed. Development of the super-cavity and the experimental results of X-ray generation will be presented at the conference.
POSTECH, Pohang, Kyungbuk
PAL, Pohang, Kyungbuk
NFRI, Daejon
Funding: This work is supported by KAPRA and POSTECH Physics BK21 Program.
An intense L-band electron linear accelerator is now being commissioned at CESC (Cheorwon Electron-beam Service Center) for industrial applications. It is capable of producing 10 MeV electron beams with 30 kW average beam power. For a high-power capability, we adopted the traveling-wave structure operated with the 2π/3 mode at 1.3 GHz. The structure is powered by a 25 MW pulsed klystron with 60 kW average rf power. The rf pulse length is 7 μs while the beam pulse length is 6 μs due to the filling time in the accelerating structure. The accelerating gradient is 4.2 MV/m at the beam current of 1.45 A which is the fully beam-loaded condition. In this paper, we present details of the accelerator system and commissioning results.
NSC/KIPT, Kharkov
Idaho National Laboratory, Idaho
ANL, Argonne
Today accelerator driven subcritical assembly is candidate for the next generation of energy-generating nuclear facility, which could provide safe energy production, burning of transuranium elements and transmutation of radionuclides. Use of the electron beam with particle energy up to 150-200 MeV secures several advantages. Electron linear accelerators are much cheaper compared to hadron accelerators. Homogeneous irradiation of the assembly with neutrons could be provided. NSC KIPT together with ANL develops the project of a neutron source based on the sub-critical assembly driven by electron linear accelerator. Energy of electrons is 100-200 MeV. The target and assembly design is optimized to maximize the neutron source intensity with subcriticality of 0.98. Accelerator on average beam power of 100 kW, with repetition rate up to 300 Hz and pulse duration of 3,2 ms is under development. Transportation line should provide beam transfer with minimal losses of electrons and should form homogeneous distribution of the particle density at the target. Maximal value of a neutron flux is Fm=2x1013 n/(cm2s), and power of energy release in the result of nuclei fission is Pm≈ 100 kW.
Northern Illinois University, DeKalb, Illinois
ANL, Argonne
Funding: Work supported by the Department of Education under contract P116Z010035 with Northern Illinois University.
A simple, inexpensive, and compact low-energy (~20 KeV) photoemission electron source was designed, built and recently commissioned. It uses a commercial ultraviolet photocathode drive laser producing 3 ns RMS pulse. The source will eventually be used to drive a table-top THz radiation source, based on the Smith-Purcell free-electron laser scheme, and could also have potential application to time-resolved electron microcopy. We present experimental measurements of the photoemitted electron beam and numerical simulations of the anticipated parameters. We also discuss the generation of flat beams required to efficiently drive the THz radiation source.
TRIUMF, Vancouver
A personnel protection system is used to monitor the ion beam current into the experimental hall from the ISAC-II SC-linac. Two resonant capacitive pickups in the transfer line operate at the third harmonic of the bunch rate, 35.36 MHz, Ion charge, velocity and bunch width affect the sensitivity so calibration with dc Faraday cups is needed. Each monitor has a single conversion receiver with an active mixer. LO signals are provided by a frequency synthesizer locked to the accelerator synthesizer. The 1250 Hz IF signals are amplified, filtered with a 100 Hz bandwidth and amplitude detected. No image rejection is used as the background is due to on-frequency leakage from the RFQ and bunchers. An antenna in each monitor loosely couples a pulsed rf test signal to each pickup. These induced signals are mixed down to 11875 Hz, filtered, detected and used to provide watchdog signals. The measured currents are displayed through our EPICS control system which allows setting of the gain ranges, trip levels and conversion factors. The signals are also processed independently by dedicated ADC's and FPGA's to cause the Safety system to trip the beam if the current exceeds a nominal 10 nA.
CEA, Pontfaverger-Moronvilliers
Funding: CEA-DAM, Polygone d'Experimentation de Moronvilliers 51 490 Pontfaverger Moronvilliers (France). olivier.pierret@cea.fr
AIRIX is a 2 kA, 19 MeV, 60 ns, single shot linear accelerator that produces X-rays from the interaction between relativistic electrons and a Tantalum solid target (Ta). Focal spot size, integrated and temporal dose are the main characteristics that we need for the successful development of flash radiography at hydro test facilities. MTFX is a 12 bit Charge-Coupled Device (CCD) intensified camera which is equipped with a scintillator. It can give focal spot size measurements in two directions using a two dimensional wedge. By another way Mucaddix is a CVD Diamond detector which is integrated nearby the AIRIX X-ray beam source. It gives integrated dose, time resolve dose, temporal characteristics of the X-ray flash and timing of the flash respect to the start of object implosion. These two measurement systems are described and the quantified results are reviewed here.
IAP, Frankfurt am Main
Based on the 'tunnel' emittance used for electron focusing, a similar procedure with two pairs of slits with variable widths is proposed to evaluate fractional emittances and brilliances for ion beams. The measurement starts with closing both slits (one after the other), until a certain fraction of the beam current is cut out. The emittance and brilliance then is well defined for the passing beam part. Formulae are given for the emittance as well as for the brilliance in dependence of the slit width and current. This emittance measurement is free from the background subtraction problem found in the classical density measurement of phase space(s). The functions for the decrease of the emittance and for the increase of the brilliance in dependence of the transmitted beam current provide a figure of merit for the quality of the investigated beam. The device at the same time is also an adjustable emittance filter for the passing beam. At the expense of current the emittance and/or brilliance of a beam can be tailored to any value, which is available by the beam quality.
IAP, Frankfurt am Main
GSI, Darmstadt
Funding: Work supported by BMBF under contract 06FY160I.
The Heavy highly charged Ion TRAP (HITRAP) project at GSI is in the commissioning phase. Highly charged ions up to U92+ provided by the GSI accelerator facility will be decelerated and subsequently injected into a large Penning trap for cooling to the MeV/u energy level. A combination of an IH- and an RFQ-structure decelerates the ions from 4 MeV/u down to 6 keV/u. In front of the decelerator a double drift-buncher-system is provided for phase focusing and a final de-buncher integrated in the RFQ-tank reduces the energy spread in order to improve the efficiency for beam capture in the cooler trap*. This contribution concentrates on the beam dynamics simulations and corresponding measurements in the commissioning beam times up to the position of the entrance to the RFQ. Single-shot emittance measurements at higher energies using the GSI pepper pot device and construction of a new device using Micro-Channel Plate technology for low energies as well as profile measurements are presented.
*HITRAP webpage of AP division at GSI, http://www.gsi.de/forschung/ap/projects/hitrap/index_e.html
KIP, Heidelberg
MPI-K, Heidelberg
Without an adequate set of beam instrumentation, it would not be possible to operate any particle accelerator, let aside optimize its performance. In a joint effort between several major research centres, Universities, and partners from industry, DITANET aims for the development of beyond-state-of-the-art diagnostic techniques for future accelerator facilities and for training the next-generation of young scientists in this truly multi-disciplinary field. The wide research program covers the development of beam profile, current, and position measurements, as well as of particle detection techniques and related electronics. This contribution introduces this new Marie Curie Initial Training Network, presents the DITANET partner institutes, and gives an overview of the networks broad research and training program.
MPI-K, Heidelberg
CERN, Geneva
Thermo, Liverpool, New York
A thorough understanding of halo formation and its possible control is highly desirable for essentially all particle accelerators. Limiting the number of particles in the halo region of a beam would allow for minimizing beam losses and maximizing beam transmission, i.e. the experimental output. Measurements based on either optical transition radiation (OTR) or synchrotron radiation (SR) provide an interesting opportunity for high dynamic range measurements of the transverse beam profile, since the signal is linear with the beam charge over a wide range and is routinely used in many diagnostic applications. In this contribution, first results on beam halo measurements obtained from a flexible core masking technique and an innovative CID camera system are summarized.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
At SPring-8, the 8 GeV linac for an X-ray free electron laser (XFEL) is now under construction. In order to realize the XFEL, highly qualified electron beams are required. A measurement of spatial structure of such beam is very important for the beam tuning of XFEL. The spatial structure is measured with a screen monitor, which we now develop. The resolution of the measurement is required within 10 um. The screen monitor comprises a vacuum chamber with a thin metal (100 um, SUS) foil to emit OTR, lenses for focusing and a CCD camera system. The main feature of the monitor is a bright and high-resolution optical system. In order to realize this system, the lenses are placed close to the foil, the distance between the lenses and the foil is 100 mm, and the lenses have a large diameter (2 in.). This optical-geometrical structure also contributes much to reduce the airy radius of a near field image. Although the range of an observation wavelength is wide as which is form 400 to 800 nm, the resolution of the measurement on the foil is calculated as 2.5 um. The experimental data of the developed screen monitor also suggested the same resolution.
JASRI/SPring-8, Hyogo-ken
At the SPring-8 1 GeV linac, a beam current or charge is measured by means of an integrator circuit. A signal from a current transformer is processed into an integrated voltage. The Fast Gated Integrator and Boxcar Averager Module (Stanford Research Systems) is presently used as the integrator. However we plan to expand a dynamic range and an integration time of the integrator. Because the noise level of the present integrator becomes too large for the expansion, we developed a low-noise and high-resolution integrator. Both the present and developed integrators have the same functions such as signal gating, accumulation of analog signal and sample hold. The principal noise of the integrator was found to be a switching noise of the gate switch. To reduce the switching noise a GaAs transfer switch SW-283-PIN (M/A-COM) was adopted as the gate switch. The experimental data of the developed integrator showed 1/10 of the noise level of the present integrator.
KEK, Ibaraki
A new beam-charge interlock system has been developed for radiation safety and machine protection at the KEKB injector linac. Although the previous software-based interlock system was working, it was replaced by the new hardware-based one. The new interlock system restricts the integrated amount of beam charges delivered to four different storage rings (KEKB e+, KEKB e-, PF, PF-AR) at six locations along the linac. When the integrated amount of beam charges exceeds a certain threshold level prescribed at each location, the beam-abort requests are directly sent through a twisted hardwire cable to the safety control system of the linac. The new interlock system boosted its reliability in comparison with the previous system. The full-scale operation of the new interlock system has been started since the end of March 2008. In this report we describe the operational performance of the new beam-charge interlock system.
KEK, Ibaraki
A new nondestructive bunch-length monitor has been numerically investigated. The monitor detects electromagnetic fields generated through a ceramic gap of a vacuum pipe when a charged particle beam passes through the pipe gap. The frequency spectrum of the electromagnetic fields detected in wave zone spreads over a millimeter-wave length from a microwave length region for a short pulse beam with a bunch length of pico-second region. The frequency spectrum strongly depends on the bunch length of the relativistic charged beam if the geometrical structure of the pipe gap is fixed. The detection principle of the bunch-length monitor and some numerical analysis results applied to a single-bunch electron beam of the KEKB injector linac are described in this report.
CERN, Geneva
In the CLIC Test Facility 3 (CTF3), the strong coupling between the beam and the accelerating cavities (full beam loading) induces transient effects such that the head of the pulse is accelerated almost twice as much as the steady-state part of the pulse. The beam optics in the machine is tailored for the steady-state and not for the higher energy electrons, which are gradually lost. This can lead to inefficiency and contributes to the activation of the machine. A beam loading compensation scheme has been proposed to minimize this effect. By delaying appropriately the arrival time of rf pulse in accelerating cavities with respect to the beam, the transient energy can be brought close (to within a few percent) of the steady-state one. This paper presents the measurements done on CTF3 using time resolved energy measurements.
CERN, Geneva
NU, Evanston
The CLIC Test Facility CTF3, being built at CERN by an international collaboration, should demonstrate the feasibility of the CLIC two-beam technology by 2010. One of the issues addressed is the control of the electron bunch length in the whole complex. A bunch length measurement system with good resolution is therefore paramount. Two different systems are presently used in CTF3, based on microwave spectroscopy and on transverse rf deflectors, respectively. In the paper we describe the two systems, we discuss the different experimental methods used and present the results of the latest measurement campaigns.
CERN, Geneva
MPQ, Garching, Munich
Linac 4 is a 160 MeV H- linac which will become the new injector for CERN's proton accelerator chain. The linac will consist of 4 different rf structures, namely RFQ, DTL, CCDTL and PIMS running at 352.2 MHz with 2 Hz repetition rate and 0.4 ms pulse length. A chopper line ensures clean injection into the PS Booster. The combination of high frequency and a high-current, low-emittance beam calls for a compact design where minimum space is left for diagnostics. On the other hand, diagnostics is needed for setting up and tuning of the machine during both commissioning and operation. A measurement strategy and the corresponding choice of the diagnostic devices and their specific use in Linac4 are discussed in this paper.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
Funding: Work supported by EU/FP6/CARE (HIPPI) RII3-CT-2003-506395
Among present challenges for beam diagnostics and instrumentation are issues presented by high beam intensity, brightness, resolution and the need to avoid inserting mechanical parts into the beam. This very often means applying non-destructive methods, which avoid interaction between ions and mechanical parts and, furthermore, allow on-line measurements during normal beam operation. The preferred technique for H- beams is the photo-detachment process where (laser) light within the range of 400-1000 nm has a sufficient continuous cross section to neutralize negative ions. The actual diagnostics are then applied to either the neutrals produced or the electrons. The latter are typically used for beam profiles whereas neutrals are more suitable for emittances, and form the subject of the present paper. This provides an overview of the basic features of the diagnostic technique, followed by a more intensive discussion of some experimental and theoretical aspects with emphasis on computing the 4 dimensional emittance using a method called Maximum Entropy (MaxEnt).
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357.
We have developed a pepper pot - scintillator screen system to measure the emittance of low-energy dc beams extracted from an ECR ion source and post-accelerated to an energy of 75 - 90 keV/charge. Different scintillators have been tested and CsI (Tl) was chosen due to its high sensitivity, wide dynamic range and long life-time. The linearity of both the scintillator and the CCD camera has been studied. A LabVIEW code has been developed and used for on-line emittance measurements. Un-normalized rms emittances measured for 209Bi20+ and 209Bi21+ beams with current of 1.0 - 1.5 pnA are usually ~30 π mm.mrad. A complicated structure of multiple images of individual holes has been observed. The innovative combination of a special type of scintillator, a CCD camera and a fast shutter allowed us to create a very efficient emittance meter for low-energy dc ion beams. Using on-line emittance measurements, it was possible to improve the beam quality by re-tuning the ion source conditions. Because of the two-dimensional array of holes in the pepper-pot, this emittance meter can be used to observe and study four-dimensional emittance correlations in beams from ECR ion sources.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Characterization of the micropulse bunch lengths and phase stability of the drive laser and the electron beam continue to be of interest at the Fermilab A0 Photoinjector facility. Upgrades to the existing Hamamatsu C5680 streak camera were identified, and initially a synchroscan unit tuned to 81.25 MHz was installed to provide a method for synchronous summing of the micropulses from the drive laser and the optical transition radiation (OTR) generated by the e-beam. A phase-locked delay box was also added to the system to provide phase stability of ~1 ps over tens of minutes. Initial e-beam measurements identified a significant space-charge effect on the bunch length. Recent measurements with a re-optimized transverse emittance allowed the reduction of the micropulse number from 50 to 10 with 1 nC each to obtain a useful streak image. This increased signal also would facilitate dual-sweep operations of the streak camera to explore macropulse effects. Installation of the recently procured dual-sweep module in the mainframe has now been done. Initial commissioning results and sub-macropulse effects in the beams will be presented as available.
Fermilab, Batavia
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Strong enhancements of the optical transition radiation (OTR) signal sampled after bunch compression in the Advanced Photon Source (APS) linac chicane have been observed as has been reported in LCLS injector commissioning. A FIR CTR detector and interferometer were used to monitor the bunch compression process of the PC gun beam down to sub-0.5 ps (FWHM) and correlate the appearance of spatially localized spikes of OTR signal (5 to 10 times brighter than adjacent areas) within the beam image footprint. We also observed that a beam from a thermionic cathode gun with much lower charge per micropulse (but a similar total macropulse charge to the PC gun) showed no enhancement of the OTR signal after compression. Reconstructions of the temporal profiles from the autocorrelations of both beams were performed and will be presented. Spectral-dependence measurements of the enhanced OTR were done initially at the 375-MeV station using a series of bandpass filters inserted before the CCD camera. Tests with an Oriel spectrometer with ICCD readout are now being planned to extend those studies. Discussions of the possible mechanisms for the OTR enhancements will be presented.
JLAB, Newport News, Virginia
When operating JLab high current ERL a strong reduction of the FEL efficiency was observed when increasing the average electron beam current. Investigating the FEL efficiency drop-off with the electron beam average current we also have measured the electron beam phase noise and the fast energy modulations. The so-called phase noise is essentially a variation of the time arrival of the electron bunches to the wiggler. That could be a very effective way of reducing the FEL efficiency if one takes in to account that the accelerator is routinely operated with the RMS bunch length of about 150 fs. Under a fast energy modulation we mean a modulation which can not be followed by the FEL due to its time constant, defined by the net gain. Such a modulation also could be a possible cause of the efficiency drop-off. Having the measurements made we could rule out the FEL efficiency drop-off due to either the fast energy modulation or the phase modulation. We also have learned a lot about instrumentation and techniques necessary for this kind of beam study. In this contribution we describe the used instrumentation and present results of the measurements.
JLAB, Newport News, Virginia
CASA, newport news
Fermilab, Batavia
Optical diffraction radiation (ODR) is a promising technique, which could be used for non interceptive beam size measurements at future light sources. An ODR diagnostic station was designed and installed on a CEBAF transfer beam line. The purpose of the setup is to evaluate experimentally the applicability range for an ODR based non interceptive beam size monitor and to collect data to benchmark numerical modeling of the ODR. An extensive set of measurements were made at the electron beam energy of 4.5 GeV. The ODR measurements were made for both pulsed and CW electron beam of up to 80 uA. The wavelength dependence and polarization components of the ODR were studied using a set of insertable bandpass filters and polarizers. The typical transverse beam size during the measurements was ~150 microns. Complete ODR data, wavelength and polarization, were recorded for different beam sizes and intensities. The beam size was also measured with an optical transition radiation (OTR) as well as wire scanner located next to the ODR station. In this contribution we describe the experimental setup and present first results of the measurements with the comparison to the numerical simulations.
ORNL, Oak Ridge, Tennessee
Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
Charged-particle beam diagnostic devices such as wire scanners, wire harps, and laser scanners all provide data sets describing the one-dimensional density distributions of the beam at a particular location; these data are commonly called profile data. We use these data for further computations, usually beam properties such as position and size, but to do so requires a certain level of accuracy in the data. Thus, we must make real world considerations as to its information content. Specifically, we consider noise in the data and the fact that it is sampled. The operation of a typical profile device is outlined in order to create a general model for the data sets. Using signal processing techniques we identify the minimal sampling requirements for maintaining information content. Using Bayesian analysis we identify the most probable Gaussian signal within the data (the mean and standard deviation of the Gaussian signal can then be used for computations). Time permitting we present techniques for direct computation of beam properties using noisy, sampled profile data.
BNL, Upton, Long Island, New York
A beam profile and energy monitor for H- beams based on laser photoneutralization is being developed at Brookhaven National Laboratory for use on the High Intensity Neutrino Source at Fermilab. An H- ion has a first ionization potential of 0.75 eV and can be neutralized by light from a Nd:YAG laser (λ = 1064 nm). To measure beam profiles, a narrow laser beam is stepped across the ion beam removing electrons from the portion of the H- beam intercepted by the laser. A curved axial magnet field channels these electrons into a Faraday cup. To measure the energy spread of the electrons the laser position is fixed and the voltage on a screen in front of the cup is raised in small steps. We deduce the energy spread of the H- beam by deconvolving the electron spectrum into components from beam energy and from space-charge fields. Measurements are reported from experiments in the BNL linac MEBT at 750 keV.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
CEA, Gif-sur-Yvette
INFN-Roma II, Roma
ENEA C.R. Frascati, Frascati (Roma)
SOLEIL, Gif-sur-Yvette
INFN-Roma, Roma
UCLA, Los Angeles, California
DESY, Hamburg
Funding: Work partially supported by the EU Commission in the sixth framework program. Contract No. 011935 EUROFEL and MIUR(Research Department of Italian Government).
An intense activity on high brilliance photo-injectors for SASE-FEL experiments and facilities, is being carried out, since 2003, in the research site of the INFN Frascati Laboratory, Rome, in collaboration with CNR and ENEA. The SPARC project, a 150 MeV photo-injector, is currently in advanced phase of commissioning. The electron beam, which drives a 530 nm FEL experiment, is being characterized in terms of emittance, energy spread, peak current. The matching with the linac confirmed the theoretical prediction of emittance compensation based on the invariant-envelope matching. The demonstration of the velocity-bunching technique is in progress too. The SPARC photo-injector is the test facility for the soft-X FEL project named SPARX, that is based on the generation of ultra high peak brightness electron beams at the energies of 1.2 and 2.4 GeV generating radiation in the 1.5-13 nm range. SPARX will be realized in the Tor-Vergata University campus. In this paper we report the experimental results obtained so far with SPARC and the design status of the SPARX project.
ISIR, Osaka
KEK, Ibaraki
HU/AdSM, Higashi-Hiroshima
Funding: This research is partly supported by the accelerator support program to universities conducted by the High Energy Accelerator Research Organization in Japan.
We have begun a three-year project to develop a photocathode rf electron gun for the 40 MeV L-band linac at ISIR, Osaka University in collaboration with KEK. The L-band linac with an rf frequency of 1.3 GHz is equipped with a thermionic electron gun and it can accelerate a high-intensity single-bunch electron beam with charge up to 91 nC/bunch. Because the large emittance of ~100 pi mm x mrad is a limiting factor in the experiments, it is required to develop a new electron gun capable of providing an electron beam with much lower emittance. Since a group at the Accelerator Laboratory of KEK is developing a photocathode rf electron gun in the L-band for the International Linear Collider Project, we have joined the group to learn how to develop such an rf gun and also to obtain support from KEK. In this first year, characteristics of the rf gun will be measured at KEK for ILC fabricated by FNAL. We plan to optimize the structure of the rf gun for ISIR with computer simulation. We will report the plan and progress to develop a photocathode rf gun for the L-band linac.
RISE, Tokyo
KEK, Ibaraki
University of Tokyo, Tokyo
ISIR, Osaka
HU/AdSM, Higashi-Hiroshima
AIST, Tsukuba, Ibaraki
Funding: Work supported by MEXT High Tech Research Project HRC707, JSPS Grant-in-Aid for Scientific Research (B)(2) 16340079
At Waseda University, we have been developing a high quality electron source based on photo-cathode rf gun which has a Cs-Te cathode with high quantum efficiency. Until now, at the Waseda University we have succeeded the soft X-ray generation via inverse-Compton scattering and pulse radiolysis system for studying the early processes of radiation chemistry with electron beams generated by copper cathode rf gun. Cs-Te rf gun is expected to generate higher charge electron bunches with a low emittance than a copper cathode because of its high quantum efficiency and also the high-quality multi-bunch electron beams. That enables us to extend the range of electron beam parameters for our application experiments. However, a Cs-Te cathode has a short life compared with a copper, so it has to be exchanged occasionally, thus we have developed a new rf-gun cavity which can be attached the compact cathode load-lock system. Moreover, we improved the design of an existing rf-gun cavity for the reduction of the dark current and the higher electric field. In this conference, the performance of the improved cavity and the result of electron beam generation experiments will be reported.
RAS/INR, Moscow
DESY, Hamburg
DESY Zeuthen, Zeuthen
During development and operation of DESY L-band rf gun cavities, desires for further improvements were formulated. The next step of development is based on the proven advantages of existing cavities, but includes significant changes. The L-band 1.6 cell rf gun cavity is intended for operation in pulse mode with electric fields at the cathode of up to 60 MV/m, rf pulse length of ~1 ms and average rf power higher than existing gun cavities. In the new design the cell shape is optimized to have the maximal surface electric field at the cathode and lower rf loss power. The cavity cells are equipped with rf probes. Cooling circuits are designed to combine cooling efficiency with operational flexibility. In the report, the main design ideas and simulation results are described.
PSI, Villigen
Paul Scherrer Institute (PSI) is presently developing a low emittance electron source for the PSI-XFEL project. The electron gun consists of an adjustable diode configuration subject to pulses of 250 ns (FWHM) with amplitude up to 500 kV from an air-core transformer- based high-voltage pulser. The facility allows high gradient tests with different cathode configurations and emission processes (field emission and photo emission). In the first stage, the beamline is only made up of focussing solenoids followed by an emittance monitor. Selected beam characterization measurements, from photo-cathode operation driven by a 266 nm UV laser system delivering 4 uJ energy during 6.5 ps (FWHM), are presented and compared to the results of 3D particle tracking simulations.
UMAN, Manchester
The Hashemite University, Zarka
Based on Lienard-Weichert method of retarded potentials and the potential due to the image of charges on the cathode, a rigorous relativistic description of the beam transport inside the rf-photoinjector is presented. The velocity dependent effects are explicitly taken into account in a complete analytical description. Simulations are presented for parameters of the ELSA photo-cathode.
Diamond, Oxfordshire
Many X-ray Free Electron Laser (XFEL) projects are under construction or are being proposed. A photoinjector with low transverse emittance is one of the key elements for successful XFEL operation. For the last two decades, photoinjectors have been developed to reach the XFEL requirement, typically with a normalised emittance of 1 mm mrad for a 1 nC bunch and high peak current. Here, we make a further numerical optimization of an S-band photoinjector to achieve 0.5 mm mrad for 1 nC bunch in a structure that should permit high repetition rates to be achieved. Optimizations for alternative operation conditions with lower charge and lower emittance are also shown.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An energy recovery linac based light source is a potential revolutionary upgrade to the Advanced Photon Source (APS) at Argonne National Laboratory. The concept relies on several key research areas, one of which is the generation of ultra-low emittance, high-average-current electron beams. In this paper, we present our investigation of a dc-gun-based system for ultra-low emittance bunches in the 20 pC range. A parallel multi-objective numerical optimization is performed in multi-parameter space. Parameters varied include experimentally feasible drive-laser shapes, the dc gun voltage, and the thermal energy of the emitted photo-electrons. Our goal is to deliver a 10 MeV, 20 pC bunch at the entrance of the linac with an emittance of 0.1 μm or lower, rms bunch length of 2 to 3 ps, and energy spread no larger than 140 keV. We present the machine parameters needed to generate such an injector beam, albeit without a merger.
LBNL, Berkeley, California
Università Cattolica-Brescia, Brescia
Funding: US Deparment of Energy
The photocathode R&D program at Lawrence Berkeley National Laboratory is presented, including the status of the lab and experimental results. We will also present experimental result obtained at Brescia Italy and theoretical work on predicting minimum thermal emittance from metal cathodes and emittance growth due to stochastic Coulomb interaction.
Northern Illinois University, DeKalb, Illinois
Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University
We discovered, by modeling the AES/JLab direct-current photoinjector with several beam-simulation codes, that nominal injector settings would create a large diffuse beam halo as a consequence of the internal space-charge force in the beam. The injector-induced halo is sensitive to the injector settings, but if the settings are judiciously chosen, it can be largely circumvented. We present an exploration of the parameter space for the AES/JLab photoinjector. Measurement of beam halo will be a crucial aspect of commissioning this machine.
Northern Illinois University, DeKalb, Illinois
Fermilab, Batavia
LBNL, Berkeley, California
Funding: Work supported by Fermi Research Alliance LLC. Under DE-AC02- 07CH11359 with the U.S. DOE and by the Department of Education under contract P116Z010035 with Northern Illinois University
Fermilab is currently constructing a GeV-scale electron accelerator test facility. The accelerator will serve as a backbone for several Fermilab R&D programs, e.g., to test subsystem associated to project-X, ILC and the muon collider program. It is also anticipated that this facility will support beam physics and accelerator R&D programs such as testing of novel acceleration techniques, beam diagnostics and radiation sources concepts. In this paper we describe a possible option for the electron injector based on a photoemission rf gun. Optimization and performance studies of this ~50 MeV photoinjector are performed with various tracking programs (Astra, GPT, Impact-T, Impact-Z). We explore the performances of the magnetic bunch compressor which is extremely challenging at 50 MeV due to strong phase space dilution via collective effects (space charge and coherent synchrotron radiation). We also investigate the generation of flat beams with very high transverse emittance ratio using a round-to-flat beam transformer.
Northern Illinois University, DeKalb, Illinois
JLAB, Newport News, Virginia
Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University
The photoinjector of the JLab 10 kW IR FEL was recently upgraded: a new photocathode drive laser was commissioned and the booster section was replaced with 7-cell cavities. In this paper we present numerical simulation and optimization of the photoinjector perform with ASTRA, IMPACT-T and IMPACT-Z beam dynamics codes. We perform these calculations for two operating voltage of the dc gun: the nominal 350 keV and the planned 500 keV operating points.
Northern Illinois University, DeKalb, Illinois
Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University
From the prospect of the high average current electron injectors, the most important advantage of the field-emission cathodes is their capability to generate very large current densities. Simulation of field-emission cathodes is complicated by the large range of spatial dimensions: from sub-micron scale, for a single field-emission tip, to millimeter scale, for a field-emitter array. To overcome this simulation challenge our numerical model is split in two steps. In the first step, only electrons emitted by a single tip are considered. In the second step, the beams originating from many single emitting tips are merged together to mimic the field-emitter array configuration. We present simulation results of injector based on field array emitters cathodes.
Fermilab, Batavia
Northern Illinois University, DeKalb, Illinois
Euclid TechLabs, LLC, Solon, Ohio
ANL, Argonne
Funding: Work supported by US. Department of Energy, under Contract No. DE-FG02-06ER41435 with Northern Illinois University.
We present a diagnostics suite and analyze techniques for setting up the longitudinal beam dynamics in ILC electron injectors and bunch compressors. Techniques to measure first order moment and recover the first order longitudinal transfer map of the injector intricate bunching scheme are presented. Coherent transition radiation diagnotics needed to measure and monitor the bunch length downstream of the ~5 GeV bunch compressor are investigated using a vector diffraction model. We finally introduce a new diagnostics capable of measuring time-transverse correlation along a single bunch. Such a diagnostics should be valuable for controlling emittance dilution via transverse wakefield and for properly setting the crab cavities needed for maximizing luminosity for non-zero crossing angle at the interaction point.
LANL, Los Alamos, New Mexico
AES, Medford, NY
Funding: This work is supported by ONR and HEL-JTO.
The LANL/AES 2.5-cell, normal-conducting radio-frequency (NCRF) injector has been fabricated. This room-temperature injector can be used to generate cw electron beams with average current greater than 100 mA and beam energy up to 2.5 MeV prior to injection into an energy-recovery linac. PARMELA simulations show the effectiveness of emittance compensation in generating high-brightness electron beams at relatively low accelerating gradients. We present the initial measurement results of the rf, accelerator and vacuum properties of the NCRF injector and the associated ridge-loaded waveguides. The impact of these rf measurement results on the planned thermal and electron beam tests will also be discussed.
UW-Madison/SRC, Madison, Wisconsin
Funding: This work is supported by the University of Wisconsin-Madison and MIT, and by the US NSF under award No. DMR-0537588
The Wisconsin FEL project is a 2.2 GeV, HHG seeded, FEL designed to provide six individual beamlines with photons from 5 to 900 eV. The FEL requires electron bunches with 1 kA peak bunch current and less than 1 mm*mrad transverse slice emittance. To meet those requirements a low frequency, SRF electron gun is proposed which uses "blow-out" mode bunches*. Blow-out mode produces ellipsoidal bunches which are easily emittance compensated**. They also have a very smooth density and energy distribution. Results of the modeling of the injector and a diagnostic beamline will be presented.
* O.J. Luiten, et al., Phys. Rev. Lett., 93, 094802-1 (2004)
** C. Limborg-Deprey, P. Bolton, NIM-A, 557 (2006) 106-116
SLAC, Menlo Park, California
Funding: Work supported by DOE contract DE-AC02-76SF00515
In high charge rf photo-injectors, due to the strong longitudinal space charge, bunch lengthening can readily occur. This paper presents beam dynamics studies of such bunch lengthening and methods to compensate it. With these methods, not only can the bunch length be preserved, but it can be shortened at the photo-injector exit.
University of Pennsylvania, Philadelphia, Pennsylvania
Fermilab, Batavia
The Fermilab A0 Photoinjector is a 16 MeV high-intensity, low emittance electron linac used for advanced accelerator R&D. To achieve a high quality beam here it is important to maintain a stable laser in terms of both intensity and timing. This paper presents our measurement of the laser timing jitter, which is the random late or early arrival of the laser pulse. The seed laser timing jitter has been measured to less than 200 fs, by examining the power spectrum of the signal of a fast photodiode illuminated by it. The pulsed and pumped laser timing jitter has been measured with limited resolution to less than 1.4 ps, by examining the phase of a cavity impulsively excited by the signal from a fast photodiode illuminated by the laser pulse.
Rutgers University, The State University of New Jersey, Piscataway, New Jersey
Fermilab, Batavia
Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
An experiment has been developed at the Fermilab A0 Photoinjector Lab to demonstrate the exchange of longitudinal emittance with the horizontal emittance. Our apparatus consists of a 3.9 GHz TM110 deflecting rf cavity placed between two magnetic dogleg channels. The first dogleg generates the needed dispersion to appropriately position the off-momentum electrons in the TM110 cavity. The TM110 cavity reduces the momentum spread and imparts a time dependent transverse kick. The second dogleg finishes the exchange and yields the exchange of the emittances. We report on the measurement of the exchange beamline matrix elements as well as an inital report on measuring the exchange emittances directly.
GSI, Darmstadt
Experimental results from ion beams, extracted from an Electron Cyclotron Resonance ion source (ECRIS) are presented and compared with different models used for simulation. The model for the simulation has to satisfy different facts: The energy of ions within the plasma is in the eV-range. Electrons have a different energy distribution: there are hot electrons (up to MeV range), but also low energy electrons, responsible for charge neutrality within the plasma. Because the gyration radius of ions is within the mm-range and below, ions can be extracted only if they are located on a magnetic field line which goes through the extraction aperture. Because of the gradient dBz/dz of the mirror field only these ions can be extracted, which have enough energy in direction of the field line. These conditions are fulfilled for ions which are going to be lost through the loss cone created by the hexapole. The extracted beam shows a typical behavior for an ECRIS: when the beam is focused by a lens (here a solenoid) directly behind extraction, the initial round and hollow beam develops wings with a 120-degree symmetry. These wings has influence on the beam emittance.
Kyoto ICR, Uji, Kyoto
We aim to develop a small and high intensity proton source for a compact accelerator based neutron source. Because this proton source shall be located close to RFQ for simplification, ratio of H+ to molecular ions such as H2+ or H3+ must be large. Therefore we select ECR ion source with permanent magnet as a small and high intensity ion source. ECR ion sources can provide high H+ ratio because of their high plasma temperature. Using permanent magnets makes the ion source small and running cost low. Because there is no hot cathode, longer MTBF is expected. Usually, gas is fed into ion sources continuously, even if ion sources run in pulse operation mode. But, continuous gas flow doesn't make vacuum in good level. So, we decided to install pulse gas valve directly to the plasma chamber. Feeding the gas only when the ion source is in operation reduces the gas load to the evacuation system and the vacuum level can be kept high. Recent experimental results will be presented.
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
Funding: This work was supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC-02-06CH11357.
An XFELO proposed recently* requires a continuous sequence of electron bunches with ultra-low transverse emittance less than 0.1 mm-mr, a bunch charge of 40 pC, an rms energy spread of 1.4 MeV, repeating at a rate between 1 MHz to 100 MHz. The bunches are to be compressed to an rms lengths less than 2 ps at the final energy of 7 GeV. Following the successful commissioning of the pulsed injector based on a thermionic gun** we discuss a concept for ultra-low emittance injector to produce 100 MHz CW electron bunches. The electron beam is extracted by ~1MV rf voltage using low frequency ~100 MHz room temperature rf cavity. The injector also includes a chicane and slits to form a short ~1 nsec bunch, a pre-buncher a booster buncher to form low longitudinal emittance of the bunched beam, an accelerating section to ~50 MeV using higher harmonic cavities, and an rf cosine-wave chopper to form any required bunch repetition rate between 1 MHz and 100 MHz. The results of initial optimizations of the beam dynamics with the focus on extracting and preserving ultra-low emittance will be presented.
*K.-J. Kim, Y. Shvyd'ko, and S. Reiche, to be published in Physical Review Letters (2008)
**K. Togawa, et al., Phys. Rev. STAB 10, 020703 (2007)
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357.
A prototype injector capable to produce multiple-charge-state heavy-ion beams is being developed at ANL. The injector consists of an ECR ion source, a 100 kV platform and a Low Energy Beam Transport (LEBT). The latter comprises two 60-degree bending magnets, electrostatic triplets and beam diagnostics stations. Several charge states of bismuth ions from the ECR have been extracted, accelerated to an energy of 1.8 MeV, separated and then recombined into a high quality beam ready for further acceleration. This technique allows us to double heavy-ion beam intensity in high-power driver linac for future radioactive beam facility. The other application is the post-accelerators of radioactive ions based on charge breeders. The intensity of rare isotope beams can be doubled or even tripled by the extraction and acceleration of multiple charge state beams. We will report the results of emittance measurements of multiple-charge state beams after recombination.
ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
Funding: *SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
During the first three years, the Spallation Neutron Source is ramping up the rep rate, pulse length, and beam current to reach 1 to 1.4 MW beam power in 2009. This challenges the Front-end with the H- source designed and built by Lawrence Berkeley National Laboratory. Early in 2007, the low-energy beam transport needed to be modified to improve the availability for duty factors in excess of 0.2%. Late in 2007, the H- source needed to be modified to produce the required 25 mA LINAC beam current during the ~0.4 ms long pulses at 60 Hz. The optimistic 1.4 MW goal requires 38 mA LINAC beam current, which was demonstrated for 4 hours on 12/24/07. LBNL developed a cesium system that uses only 30 mg of Cs to minimize the risk to the adjacent electrostatic LEBT and RFQ. Improved procedures and configuration were needed to generate intense beam currents for long pulses (>0.2 ms). Now optimal beam currents are reached within eight hours of replacing the H- source. The beam decay appears to be as small as 1% per day, which is compensated by a gradual increase in rf power. The peak performance can be restored by slowly re-cesiating the converter without interupting the neutron production.
BNL, Upton, Long Island, New York
IAP, Frankfurt am Main
Funding: Work supported by the US Department of Energy and the National Aeronautics and Space Agency
A new heavy ion preinjector is presently under construction at Brookhaven National Laboratory. This preinjector uses an Electron Beam Ion Source (EBIS), and an RFQ and IH Linac, both operating at 100 MHz, to produce 2 MeV/u ions of any species for use, after further acceleration, at the Relativistic Heavy Ion Collider, and the NASA Space Radiation Laboratory. Among the increased capabilities provided by this preinjector are the ability to produce ions of any species, and the ability to switch between multiple species in 1 second, to simultaneously meet the needs of both physics programs. Fabrication of all major components for this preinjector is in process, with testing of the EBIS and RFQ starting this year. The status of this construction will be presented.