EPAC08 - List of Keywords (single-bunch)

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single-bunch

Paper	Title	Other Keywords	Page
MOZCG01	Top-Up Operation in Light Sources	injection, storage-ring, booster, emittance	36
	H. Ohkuma JASRI/SPring-8, Hyogo-ken
	The top-up operation for user experiments has been performed at several light sources, and at most of the new light sources the top-up operation is considered in their design phase. In this paper, an overview of the top-up status in light sources is presented, including the performance of injectors for top-up in light sources, technological aspects, examples and operational data from existing machines and proposed upgrades, etc.
	Slides

MOPC046	Femtoslicing at BESSY - Detecting More Photons	laser, photon, background, electron	172
	T. Quast, K. Holldack BESSY GmbH, Berlin S. Khan Uni HH, Hamburg R. Mitzner Universität Muenster, Physikalisches Institut, Muenster
	The BESSY femtoslicing facility is now well established* and has proven its succesful operation for femtosecond laser-pump and x-ray-probe experiments*. However, many interesting physical phenomena cannot be addressed with the presently available comparably low number of photons detected at the sample. The most direct way to increase the photon flux is to increase the laser repetition rate. In order to preserve the excellent fs-signal to ps-background ratio special storage ring fill patterns and corresponding laser synchronisation schemes have been studied. We present calculations showing the influence of a dedicated new radiator promising better flux and polarisation properties. Recent results from a new beamline based on high transmission reflection zone plates will be presented. A new avalanche photo diode-array-based detection system has been successfully tested. This allows a parallel detection in the dispersion plane behind the monochomator. The status of these improvements will be presented. S. Khan et al. Phys. Rev. Lett, (97), 074801 (2006). **C. Stamm et al. Nature Mater. 6, 740 (2007).

MOPP066	Recent Experimental Study of Fast Ion Instability in ATF Damping Ring	ion, emittance, vacuum, damping	697
	N. Terunuma, Y. Honda, T. Naito, J. Urakawa KEK, Ibaraki Eckhard. Elsen, G. X. Xia DESY, Hamburg
	The Fast Ion Instability (FII) is one of the very high priorities of the damping ring R&D for the International Linear Collider (ILC). The Accelerator Test Facility (ATF) in KEK can provide an ILC damping ring-like beam. A specific FII study in ATF has been launched to characterize this phenomenon for the ILC damping ring. A new gas inlet system has been installed recently in the ATF damping ring to control the ion effect. After N2 gas injection into the vacuum chamber in south straight section of the ring, FII has been observed for elevated gas pressures. Beam size blow-up and emittance growth for various fill patterns are presented in this paper and attributed to FII. Comparison between experimental data and simulation results are given as well.

MOPP109	Status of the 100 MeV Preinjector for the ALBA Synchrotron	linac, gun, diagnostics, electron	811
	A. Falone, D. Einfeld, M. Pont ALBA, Bellaterra D. Jousse, J.-L. Pastre, F. Rodriguez, A. S. Setty THALES, Colombes A. Sacharidis EuroMev, Buc
	A turn key 100 MeV linac has been constructed by THALES in order to inject electrons into the booster synchrotron of ALBA. The linac will be commissioned in May 2008. This paper will remind the main features of the linac* and will give results obtained during the commissioning tests. The energy and emittance measurements will be done on the transfer line conceived and realized by CELLS. * D. Einfeld "Status of ALBA", PAC07, Albuquerque, USA, June 2007. ** A. Setty "Beam dynamics of the 100 MeV preinjector for the spanish synchrotron ALBA", PAC07, Albuquerque, USA, June 2007.

TUPC010	Single Bunch Studies at the Australian Synchrotron	impedance, storage-ring, synchrotron, diagnostics	1062
	R. T. Dowd, M. J. Boland, G. LeBlanc, M. J. Spencer, Y. E. Tan ASP, Clayton, Victoria
	Studies using a single high charge electron bunch have been conducted at the Australian Synchrotron to characterise the impedance of the machine at various stages of commissioning and insertion device configuration. This paper will present the results of these studies and show the time evolution of machine impedance with increasing number of insertion devices.

TUPC048	Application of a 5 GSPS Analogue Ring Sampling Chip for Low-cost Single-shot BPM Systems	pick-up, linac, electron, undulator	1167
	B. Keil, S. Lehner, S. Ritt PSI, Villigen
	In contrast to storage ring BPMs with continuously sampling ADCs, BPMs of single-bunch linear accelerators with typical repetition rates of 10-100Hz may also use waveform digitisers that sample just during a short interval when the bunch is passing the pickup. At PSI a 12-channel analogue sampling chip called "DRS" has been developed () that samples input signals in an array of 1024 capacitors per channel at up to 5GSPS. The acquisition can be stopped by a trigger signal and then the capacitor voltages of all 12 channels can be digitised with a single commercial external ADC at 33MSPS, achieving ~11 bit effective DC resolution and 450MHz max. bandwidth. The DRS chip was originally developed for low-cost digitization of 3000 detector signals of a particle physics experiment, using the PSI "VPC" VME64x FPGA board as digital back-end equipped with two PMC mezzanine modules with two DRS chips each. However, such DRS-based systems are also an attractive solution for inexpensive direct sampling and FPGA-based post-processing of suitable BPM pickup signals. This paper discusses BPM-related properties, limitations, possible improvements and measurement results of DRS-based electronics. S. Ritt. The DRS chip: Cheap waveform digitizing in the GHz range, Nucl. Instrum. Meth. A518: 470-471, 2004.

TUPC084	Combating Multi-bunch Instabilities with the Libera Bunch-by-bunch Unit	feedback, betatron, kicker, target	1251
	V. Poucki, T. Karcnik, P. L. Lemut, M. O. Oblak Instrumentation Technologies, Solkan
	Libera Bunch by Bunch is the digital processing unit for a bunch by bunch feedback system. The upgraded unit has a DSP core application featuring a 16 tap filter for each bunch. DSP processing is organized in 4 chains, following the HW implementation of A/D conversion. Besides setting of FIR filter coefficients in each processing chain, one bunch per chain can have different FIR filter coefficients and provides an option for 4 single bunch processing. All FIR filter coefficients are double buffered. Delays maximally equal to a revolution period are implemented before and after the FIR block. As an additional feature, a phase shift block is introduced that precisely shifts the phase of the output signal in the vicinity of a determined frequency. The core application is accompanied with a Matlab GUI, with an additional window for data acquisition. This system accompanied by a Front End unit provides a complete solution for combating multi bunch beam instabilities. A detailed description and results are presented.

TUPC091	Measurement of Quadrupolar Tune Shifts under Multibunch Operations of the Photon Factory Storage Ring	storage-ring, synchrotron, quadrupole, factory	1269
	S. Sakanaka, T. Mitsuhashi, T. Obina KEK, Ibaraki
	The quadrupolar tune shifts were observed under a single-bunch operation of the Photon Factory storage ring at KEK, which indicated that a quadrupolar component of wakefields affected the motion of an electron bunch. We recently measured the quadrupolar tune shifts under a multibunch operation of the Photon Factory storage ring. To detect the transverse quadrupole-mode oscillations of electron bunches, we used an avalanche photo diode (APD) which can detect visible synchrotron light with short rise-time of less than 1 ns. As a result, we observed that the quadrupolar tunes depended on the total beam current by 0.0082 1/A (in horizontal) and -0.0082 1/A (in vertical), respectively. These tune shifts can be caused by a quadrupolar component of long-range wakefield.

TUPP020	Analysis of Collective Effects at the Diamond Storage Ring	impedance, simulation, collective-effects, storage-ring	1574
	R. Bartolini, C. Christou, R. T. Fielder, M. Jensen, A. F.D. Morgan, S. A. Pande, G. Rehm, C. A. Thomas Diamond, Oxfordshire
	The Diamond storage ring has achieved its nominal operating current of 300 mA in multi-bunch mode and up to 10 mA in single bunch mode. Several collective instabilities have been observed and their dependence on machine parameters such as chromaticities, RF voltage and fill pattern have been investigated. We report here the analysis of the observed current thresholds and rise times of the instabilities compared with analytical estimates and tracking simulations. We also present the results of the MAFIA simulations performed with the aim of understanding the main contribution to the impedance of the ring and establishing a machine impedance database.

TUPP022	Measurements of Broad Band Impedance Related Longitudinal Properties of Electron Bunches at DELTA	impedance, undulator, synchrotron, klystron	1577
	R. Burek, H. Huck, G. Schmidt, T. Weis, K. Wille DELTA, Dortmund
	DELTA is a 1.5 GeV synchrotron light source which can be operated also at 550 MeV for FEL experiments. Due to interactions with the vacuum chamber, the beam induces wake fields, which act back on the beam and result in a disturbed bunch profile because of potential well distortion and turbulent bunch lengthening. These interactions limit the obtainable bunch length and achievable peak current and therefore strongly affect the FEL-operation. Recent results obtained by streak camera measurements have shown that for short bunches with maximum bunch lengths of 40 ps the longitudinal broad band impedance has to be scaled (SPEAR-scaling) to explain the measurements. The broad band impedance fits well to impedance measurements and calculations performed throughout the last years. The energy spread related to the bunch lengthening has been measured by analysing the undulator spectrum.

TUPP025	Preliminary Impedance Budget for the TPS Storage Ring	impedance, storage-ring, vacuum, coupling	1586
	A. Rusanov NSRRC, Hsinchu
	Taiwan Photon Source (TPS) is a new third generation low-emittance synchrotron storage ring which will be built at the present site of the NSRRC in Hsinchu, Taiwan. Preliminary results of the ongoing impedance studies of the TPS are presented in this paper. The overall impedance of the vacuum chamber has been evaluated with focus on the longitudinal broad-band impedance, which can lead to bunch lengthening and microwave instability. Wakepotentials and impedances produced by each component of the storage ring have been evaluated by using 3D electromagnetic code GdfidL. Then longitudinal loss factor, longitudinal broad-band impedance and transverse kick factors were computed. Results are summarized in the table. Numerically obtained data is compared to analytical results for simplified geometries of the vacuum chamber components.

TUPP028	Bunch Length and Impedance Measurements at SPEAR3	impedance, lattice, storage-ring, coupling	1595
	W. J. Corbett, W. X. Cheng, A. S. Fisher, X. Huang SLAC, Menlo Park, California
	A series of bunch length measurements have been made for different lattice configurations in SPEAR3 as a function of single-bunch current. The lattices include achromatic optics, low-emittance optics and short-bunch, low-momentum compaction optics (low-alpha). The streak-camera data clearly demonstrates effects of both resistive and reactive chamber impedance and shows levels of microwave instability threshold. In the low-alpha mode, signs of bunch length ‘bursting’ were observed. Fitted bunch-profile data, impedance calculations and bursting data are presented.

TUPP045	Studies of Beam Breakup in Dielectric Structures	focusing, simulation, quadrupole, electron	1643
	A. Kanareykin, C.-J. Jing, A. L. Kustov, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio W. Gai, J. G. Power ANL, Argonne, Illinois
	Beam breakup (BBU) effects resulting from parasitic wakefields provide a potentially serious limitation to the performance of dielectric structure based wakefield accelerators. We report on experimental and numerical investigation of BBU and its mitigation. The experimental program focuses on BBU measurements in a number of high gradient and high transformer ratio wakefield devices. New pickup-based beam diagnostics will provide methods for studying parasitic wakefields that are currently unavailable at the AWA facility. The numerical part of this research is based on a particle-Green’s function beam breakup code we are developing that allows rapid, efficient simulation of beam breakup effects in advanced linear accelerators. The goal of this work is to be able to compare the results of detailed experimental measurements with the accurate numerical results and to design an external FODO channel for the control of the beam in the presence of strong transverse wakefields.

TUPP053	Radiolocation of a HOM Source in the PEP-II Rings	vacuum, coupling, impedance, luminosity	1664
	A. Novokhatski, J. Seeman, M. K. Sullivan SLAC, Menlo Park, California
	A signal from the antenna situated in the LER (Low Energy Ring) helped to find a broken shielded bellows in the HER (High Energy Ring) during a single HER bunch operation.

WEPC027	Coherent THz Radiation at ELETTRA	radiation, electron, synchrotron, synchrotron-radiation	2043
	E. Karantzoulis, G. Penco, A. Perucchi ELETTRA, Basovizza, Trieste S. Lupi Coherentia, Naples
	Coherent infra red radiation (CIR) has been observed since some time at ELETTRA under several machine parameter settings in the beam-line SISSI. Effort has been made to produce a “stable” THz signal for experimental use. The description of the machine settings to that end and the measurements performed are presented and discussed.

WEPC030	Diamond Light Source: Moving from Commissioning to Full Machine Operation	injection, storage-ring, feedback, controls	2052
	V. C. Kempson Diamond, Oxfordshire
	Diamond Light Source commenced routine operations in January 2007 providing light to beam lines for 3000 hours in 2007 with 4000 hours planned during 2008. During shut down periods Insertion Devices and photon Beam Lines, to utilise them, are being installed at a rate of four per year. The evolution of the performance of the machine during this period is described, including beam current, vacuum levels, beam lifetime etc. Machine operational statistics are also presented including a detailed fault analysis. Efforts that have been made to improve reliability are also discussed. On behalf of the Diamond machine staff.

WEPC046	Characterizing THz Coherent Synchrotron Radiation at the ANKA Storage Ring	radiation, synchrotron, synchrotron-radiation, storage-ring	2091
	A.-S. Müller, I. Birkel, S. Casalbuoni, B. Gasharova, E. Huttel, Y.-L. Mathis, D. A. Moss, N. J. Smale, P. Wesolowski FZK, Karlsruhe E. Bruendermann Ruhr-Universität Bochum, Bochum T. Bueckle, M. Klein University of Karlsruhe, Karlsruhe
	In a synchrotron radiation source coherent infrared (IR) radiation is emitted when the bunch length is comparable to the wavelength of the emitted radiation. To generate coherent THz (far IR) radiation, the ANKA storage ring is operated regularly in a dedicated low-alpha optics. Different bunch lengths, corresponding to different spectral ranges of the THz spectrum and various electron beam energies can be offered, depending on user demand. The radiation emitted in the fringe field of a dipole magnet, the so-called edge radiation, is detected at the ANKA-IR beamline. This paper presents radiation properties like THz beam profiles and power measurements in the framework of characterising the coherent THz radiation to optimise the power, frequency and spatial output of the ANKA storage ring. First experiments showed a time averaged power of up to 0.2 mW suggesting a THz pulse peak power of at least several tens of mW.

WEPC049	Novel Schemes for Simultaneously Satisfying High Flux and TOF Experiments in a Synchrotron Light Source	kicker, synchrotron, storage-ring, radiation	2100
	D. Robin, G. J. Portmann, F. Sannibale, W. Wan LBNL, Berkeley, California
	Storage Ring Light Sources have proven to be extremeley succesful tools for probing matter. One of their most desirable features is that they are able to supply synchrotron radiation to multiple experiments simultaneously. However two classes of applications are difficult to satisfy simultaneously - high flux applications and time of flight applications. High flux experiments require filling as many buckets as possible while time of flight experiments require long gaps between bunches. In this paper we examine schemes for operating the synchrotron light source for for both communities simultaneously.

WEPC060	Studies on the Beam Current Dependent Phenomena in the BEPC-II Storage Rings	vacuum, electron, luminosity, synchrotron	2130
	Q. Qin, N. Huang, W. B. Liu, Y. D. Liu, Y. M. Peng, J. Qiu, D. Wang, J. Q. Wang, N. Wang, X. H. Wang, Y. Wei, X. M. Wen, J. Xing, G. Xu, C. H. Yu, C. Zhang, Y. Zhang, Z. Zhao, D. M. Zhou IHEP Beijing, Beijing
	The upgrade project of the Beijing Electron Positron Collider (BEPC-II) has been being commissioned since Nov. 2006. Besides the commissioning of the luminosity, which is expected to be 100 times higher than the BEPC, the BEPC-II also provided beam to the synchrotron radiation users as a light source during these two years. Some beam current dependent phenomena, such as bunch lengthening, single beam instabilities, blow-up in collision, etc., in both collision and synchrotron radiation modes are observed in the machine performance. In this paper, some observations and analyses on these phenomena are given.

WEPP073	Simulation Studies of Impact of SPS Beam with Collimator Materials	target, proton, simulation, synchrotron	2689
	N. A. Tahir GSI, Darmstadt R. W. Assmann, M. Brugger, R. Schmidt CERN, Geneva V. E. Fortov, I. Lomonosov, A. Shutov IPCP, Chernogolovka, Moscow region D. Hoffmann TU Darmstadt, Darmstadt R. Piriz Universidad de Castilla-La Mancha, Ciudad Real
	Over the past years detailed simulations were carried out to study the impact of the full LHC 7 TeV beam on a target to assess the damage caused to the equipment as a result of an accident, especially to collimators and beam absorbers, and to estimate the thickness of a sacrificial absorber that would be required to stop the beam. This study has shown that the target material will be strongly heated by the beam and transformed into plasma. It has been estimated that the beam would tunnel up to 30 m in solid copper and to about 10 m in solid carbon. Another interesting outcome of this study was that the LHC beam could be used as a tool to study High-Energy-Density (HED) states in matter. Using the same tools, we recently studied the impact of the SPS 450 GeV proton beam on tungsten and copper targets. It has been found that the material will be seriously damaged and some tunneling of the beam into the target is expected. It should be possible to validate the predictions with a test facility to deflect the high energy high intensity SPS beam on collimator and absorber materials that will become operational in the next years. N. A. Tahir et al. J. Appl. Phys. 97 (2005) 083532. *N. A. Tahir et al. Laser Part. Beams 25 (2007) 639.

WEPP136	Femtosecond and Attosecond Bunches of Electrons upon Field Emission in a Combined Quasi-static and Laser Electric Field	cathode, electron, laser, radiation	2812
	V. A. Papadichev LPI, Moscow
	Obtaining short pulses of particles and of electromagnetic radiation is of interest for investigating fast processes in physics, chemistry, biology and medicine,. A new method of modulating an electron beam is proposed to obtain electron bunches of 100-as to 20-fs duration. For this purpose, two electric fields – quasi-static and the variable field of a laser with wavelength in the 0.25 – to 10 microns range – simultaneously act on a single-spiked or multi-spiked cathode. Current from 0.01 to 100 A from one spike having a curvature radius of 1 micron corresponds to a maximal intensity of total electric field of 70 to 280 MV/cm for a 10-micron laser wavelength. For a 1-micron laser, total fields of 300 – 400 MV/cm should be used for 1 – 20 A currents. A regime of device operation was determined for which the emitting surface of a copper cathode is not damaged. Obtaining a single bunch or a sequence of bunches with a repetition rate up to1330 THz was considered. Using multi-spiked cathodes permits to obtain bunches with current up to 10 kA. P. Emma. Issues and challenges for short pulse radiation production, Proc. EPAC04, p. 225, Lucerne, Suisse. **S. Rimjuem et al. Generation of femtosecond electron pulses, Proc. EPAC04, p. 431.

THPC116	Commissioning of the iGp Feedback System at DAΦNE	feedback, betatron, controls, diagnostics	3251
	A. Drago INFN/LNF, Frascati (Roma) J. D. Fox SLAC, Menlo Park, California D. Teytelman Dimtel, San Jose M. Tobiyama KEK, Ibaraki
	The iGp (Integrated Gigasample Processor) is an innovative digital bunch-by-bunch feedback system developed by a KEK/SLAC/INFN-LNF joint collaboration. The processing unit can sample at 500 MHz and compute the bunch-by-bunch output signal for up to 5000 bunches. The feedback firmware code is implemented inside just one FPGA (Field Programmable Gate Array) chip, a Xilinx Virtex-II. The FPGA implements two 16 taps FIR (Finite Impulse Response) filter that are realtime programmable through the operator interface. At DAΦNE, the Frascati PHI-Factory, two iGp units have been commissioned in the April 2007. The iGp systems have plugged in the previous betatron feedback systems. This insertion has been very fast and has shown no problems involving just a substitution of the old, less flexible, digital unit, letting unchanged the baseband analog frontend and the analog backend. The commissioning has been very simple, due to the complete and powerful EPICS operator interface, working well in local and remote operations. The software includes also tools for analyzing post processor data. A description of the commissioning with the operations done to find the best feedback setup are reported.

THPC126	Performance and Features of the Diamond TMBF System	feedback, damping, controls, pick-up	3281
	A. F.D. Morgan, G. Rehm, I. Uzun Diamond, Oxfordshire
	The Diamond Transverse Multibunch Feedback System (TMBF) comprises an in-house designed and built analogue frontend to select and condition the position signals for each bunch. This is combined with the Libera Bunch-by-Bunch system to digitise the signal and perform the relevant calculations before driving the output stripline kickers. As the electronics are based on an FPGA this has allowed us to implement several features in addition to the basic feedback calculations. We report on improvements to both the analogue and digital parts of the TMBF system, along with recent achievements in using the system for instability mode stabilisation and for tune measurement. Also we discuss the potential of the system and additional functionality we plan on introducing in the near future.

FRXBGM01	Impedance Computation and Measurement in Modern Storage Rings	impedance, storage-ring, simulation, kicker	3728
	R. Nagaoka SOLEIL, Gif-sur-Yvette
	Recent progress in the evaluation of machine impedance and instability thresholds will be reviewed, and comparisons made between measurements and predicted impedance in recently commissioned storage rings.
	Slides