A   B   C   D   E   F   G   H   I   K   L   M   O   P   Q   R   S   T   U   V   W   X    

CSR

   
Paper Title Other Keywords Page
MOPCH013 Slice Emittance Measurements at FLASH emittance, quadrupole, DESY, RF-structure 77
 
  • M. Roehrs, C. Gerth, M. Huening, H. Schlarb
    DESY, Hamburg
  The SASE process in Free Electron Lasers mainly depends on time-sliced parameters of charge density, energy spread and transverse emittance. At the VUV-FEL at DESY, electron bunches are compressed longitudinally in two magnetic chicanes in order to achieve high peak currents. The compression causes considerabe variations in slice emittance along the bunches. The vertically deflecting rf-structure LOLA, which is in operation at the VUV-FEL since early 2005, allows to resolve longitudinal variations in horizontal slice width for single bunches. The horizontal slice emittances can be determined by additionally varying the strengths of the quadrupoles upstream of LOLA. Results of slice emittance measurements using different bunch compression schemes are presented.  
 
MOPCH014 Energy-time Correlation Measurements Using a Vertically Deflecting RF Structure acceleration, emittance, FEL, DESY 80
 
  • M. Roehrs, C. Gerth, M. Huening, H. Schlarb
    DESY, Hamburg
  To initiate the lasing process in SASE-based Free Electron Lasers, electron bunches with high peak currents are necessary. At the VUV-FEL at DESY, high peak currents are produced by bunch shortening in magnetic chicanes induced by a linear energy-time gradient. The residual uncorrelated time-sliced energy width after compression is a crucial parameter for the lasing process. The final energy-time correlation provides important information about the compression process. This paper presents a measurement of slice energy spread and energy-time correlation using a vertically deflecting rf-structure (LOLA). The structure allows to map the time delay of bunch slices to the vertical axis of a screen. After dispersing the bunches horizontally with a dipole, the energy-time correlation can be directly obtained in a single shot measurement. Results for different bunch compression schemes are presented. The measured bunch length in case of a non-compressed beam is compared to streak camera measurements.  
 
MOPCH049 Trajectory Stability Modeling and Tolerances in the LCLS LCLS, quadrupole, linac, undulator 151
 
  • J. Wu, P. Emma
    SLAC, Menlo Park, California
  To maintain stable performance of the Linac Coherent Light Source X-ray Free-electron laser, one has to control undulator trajectory stability to a small fraction of the rms beam size. BPM based feedback loops running at 120 Hz will be effective in controlling jitter at low frequencies less than a few Hz. On the other hand, linac and injector stability tolerances must control jitter at higher frequencies. In this paper, we study the possible sources of such high frequency jitter, including: 1) steering coil current regulation; 2) quadrupole (and solenoid) transverse vibrations; 3) quadrupole (and solenoid) current regulation in presence of typical 200-micron misalignments; 4) charge jitter coupling to RF cavity transverse wakefield due to alignment errors; and 5) bunch length jitter coupling to Coherent Synchrotron Radiation in Chicane. Based on this study, we then set tolerances on each item.  
 
MOPCH055 Circulation of a Short, Intense Electron Bunch in the NewSUBARU Storage Ring linac, injection, storage-ring, radiation 163
 
  • Y. Shoji, Y. Hisaoka, T. Matsubara, T. Mitsui
    NewSUBARU/SPring-8, Laboratory of Advanced Science and Technology for Industry (LASTI), Hyogo
  • T. Asaka, S. Suzuki
    JASRI/SPring-8, Hyogo-ken
  One new method is proposed which supplies synchrotron radiation light from a short and intense electron bunch. This method supplies a short and intense x-ray pulse and extremely strong coherent radiation in a long wavelength region to beam lines of a storage ring. SPring-8 linac supplied a short and intense 1.0 GeV electron beam to NewSUBARU storage ring. The electron bunch was compressed to 10ps (full width) from the normal condition (20ps full width) using ECS system. The pulse charge was 0.10nC/bunch and the energy spread was (±) 0.2 % (full width) at the injection point. The ring lattice was adjusted at a quasi-isochronous condition to keep the short bunch for many revolutions. The estimated linear and non-linear momentum compaction factors were -6·10-5 (the linear factor), 0.0 (the second order factor) and +0.9 (the third order factor). The bunch length was measured by a streak camera, and the coherent radiation was detected by a Shottky diode detector. The short bunch was successfully circulated for about 50 turns.  
 
MOPCH071 Optimization of Optics at 200 MeV KEK-ERL Test Facility for Suppression of Emittance Growth Induced by CSR emittance, dipole, insertion, insertion-device 190
 
  • M. Shimada, A. Enomoto, T. Suwada, K. Yokoya
    KEK, Ibaraki
  Energy Recovery Linac (ERL) gets a lot of attention as a next period light source instrument. To produce high-brightness and short pulse synchrotoron lights, it is necessary to pass through high current and short bunch electron beams to the insertion part of ERL with keeping the low emittance and the low energy spread. However, it is challenging because Coherent Synchrotorn Radiation (CSR) generated at bending magnets is potential sources of the emittance growth which is enomous especially for high current, short bunch and a low energy beam. Therefore, it is benefit to a gradual bunch compression in the arc after accelerating the beam up to the full energy. The beam optics and lattice design of 200MeV ERL Test Facility is optimized to suppress the emittance growth caused by CSR at the arc section on two conditions, high-current mode (100mA, 1psec) and short bunch mode (0.1psec) similar to 5GeV ERL facility proposed by Cornell University.  
 
TUPCH030 A Beam Diagnostics System for the Heidelberg Cryogenic Storage Ring CSR ion, diagnostics, electron, pick-up 1067
 
  • T. Sieber, H. Fadil, M. Grieser, A. Wolf, R. von Hahn
    MPI-K, Heidelberg
  The storage of rotationally non-excited molecules and highly charged ions requires lowest temperatures and vacuum pressures. At the MPI-K Heidelberg a cryogenic storage ring (CSR) for atomic and molecular physics experiments is under development. The CSR shall allow operation at temperatures of 2 K and pressures down to 1·10-15 mbar. The ring consists of electrostatic elements and has a circumference of ~35 m. It is housed inside a large cryostat, cooled by a (20W @ 2K) Helium refrigerator. To reach low UHV pressures already at room temperature the whole machine has to be bakeable up to 300°C. These boundary conditions, together with the low charge states, low velocities and low intensities (1nA-1muA) of the ions, put strong demands on the beam diagnostics system. Some beam parameters like profile, position and intensity cannot be measured with “standard” beam diagnostics technology. Here new or further developments are required. The paper gives a general view of the beam diagnostics concept for the CSR and shows in more detail possible solutions for measurement of beam position and beam profile.  
 
TUPCH041 Electro-optic Diagnostics on the Daresbury Energy Recovery Linac electron, laser, free-electron-laser, diagnostics 1094
 
  • P.J. Phillips, W.A. Gillespie
    University of Dundee, Nethergate, Dundee, Scotland
  • S.P. Jamison
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • A. MacLeod
    UAD, Dundee
  An electro-optic longitudinal bunch profile monitor is being implemented on the 4GLS prototype energy recovery linac (ERL/p) at Daresbury Laboratories and will be used both to characterise the electron bunch and to provide a testbed for electro-optic techniques. The electro-optic station is located immediately after the bunch compressor, and within the FEL cavity; its location allows it to draw on nearby beam profile monitors and CTR and CSR diagnostics for calibration and benchmarking. We discuss the implementation and planned studies on electro-optic diagnostics with this diagnostic station.  
 
TUPCH094 THz Diagnostic for the Femtosecond Bunch Slicing Project at the Swiss Light Source electron, SLS, laser, storage-ring 1229
 
  • V. Schlott, D. Abramsohn, P. Beaud, G. Ingold, P. Lerch
    PSI, Villigen
  Interaction of electron bunches with a femtosecond Ti:Sa laser beam along a modulator wiggler in the Swiss Light Source (SLS) storage ring results in an energy modulation of the electron beam on the length scale of the laser pulse. While high energy photon pulses (3 18 keV, ~ 100 fs long) are produced by an in-vacuum undulator (radiator) and used for time resolved experiments within the SLS femtosecond bunch slicing project, coherent synchrotron radiation (CSR) emitted by the adjacent bending magnet in the THz-regime is used for longitudinal slicing diagnostics and monitoring of slicing efficiency. This paper describes the simulation and layout of the THz-diagnostic beamline and presents first time and spectrally resolved measurements with the longitudinal slicing diagnostics, which has been set-up for the SLS “femto-slicing” project.  
 
TUPLS061 Design of a Low Energy Electron Cooler for the Heidelberg CSR electron, ion, dipole, target 1630
 
  • H. Fadil, M. Grieser, D. Orlov, A. Wolf
    MPI-K, Heidelberg
  The electrostatic Cryogenic Storage Ring (CSR) is currently being designed at MPI-K in Heidelberg. This ring will utilize electrostatic deflectors and focusing elements, and will store ions with kinetic energies in the range 20~300 keV (E/Q) to be mainly utilized in atomic and molecular physics experiments. The CSR will be equipped with a compact magnetic electron cooler, which will serve the double purpose of phase space compression of the stored ion beam as well as an electron target for recombination experiments. The cryogenic photocathode source, developed for the Heidelberg TSR, will be used to provide extremely cold magnetically guided electron beams. The maximum cooling electron energy is 165 eV and the usual operation energy for 20 keV protons will be about 10 eV. The cooler will fit in the 2.8 m straight section of the ring. The device will be installed inside the outer vacuum chamber of the CSR, and the magnetic confinement of the electrons will be provided with high temperature superconducting coils. The design of the magnets of the CSR electron cooler will be presented in this paper.  
 
WEYFI01 Modelling of Space Charge and CSR Effects in Bunch Compressor Systems simulation, space-charge, emittance, radiation 1897
 
  • M. Dohlus
    DESY, Hamburg
  Bunches with high peak currents of the order of kilo-Amperes are required in linac based X-ray free electron lasers. These bunches cannot be produced directly in guns because space charge forces would destroy the brilliance within a short distance. Therefore bunches with a peak current of a few tens of Amperes are created in laser-driven radio-frequency sources and are compressed in length by two orders of magnitude. In most designs, the compression is achieved in magnet chicanes, where particles with different energies have different path lengths so that a bunch with an energy distribution correlated with longitudinal particle position can shrink in length. The principle problem is that short bunches on curved trajectories will emit coherent synchrotron radiation (CSR). The CSR effects and the space charge fields play an important role in the particle dynamic and the design of a bunch compression system. This presentation will provide an overview of computational methods and simulation tools for space charge and coherent synchrotron radiation effects in magnetic bunch compression systems.  
slides icon Transparencies
 
WEOFI03 Beam Dynamics Simulation in e- Rings in SRFF Regime simulation, vacuum, lattice, synchrotron 1908
 
  • L. Falbo
    INFN-Pisa, Pisa
  • D. Alesini
    INFN/LNF, Frascati (Roma)
  • M. Migliorati
    Rome University La Sapienza, Roma
  The concept of strong RF focusing has been recently proposed to obtain locally short bunches in electron/positron colliders, by modulating the longitudinal bunch dimensions along the rings. To study the single bunch dynamics, a macroparticle numerical code has been written which simulates the effects of the objects generating broad band impedance along the ring and the effects of the coherent synchrotron radiation in dipoles and wigglers. The obtained results are shown and discussed.  
slides icon Transparencies
 
WEPCH018 Finite Elements Calculations of the Lattice and Ring Acceptance of the Heidelberg CSR quadrupole, lattice, ion, storage-ring 1960
 
  • H. Fadil, M. Grieser, A. Wolf, R. von Hahn
    MPI-K, Heidelberg
  A new Cryogenic Storage Ring (CSR) is currently being designed at MPI-K in Heidelberg. This electrostatic ring, which will store ions in the 20~300 keV energy range (E/Q), has a total circumference of 35.2 m and a straight section length of 2.8 m. The ring design was at first carried out with the optics code MAD in the first order approximation. Further investigation of the optics was performed with the finite elements electrostatic code TOSCA. The individual elements of the CSR (deflectors and quadrupoles) were calculated then a model of the entire ring was simulated with successful storage (tracking) of 20keV protons for many turns. The lattice parameters thus obtained were compared with the MAD results and show good agreement. The dynamic ring acceptance was also calculated for the standard operating point.  
 
WEPCH021 Generalized Twiss Coefficients Including Transverse Coupling and E-beam Growth undulator, electron, emittance, radiation 1966
 
  • F. Ciocci, G. Dattoli
    ENEA C.R. Frascati, Frascati (Roma)
  • M. Migliorati
    Rome University La Sapienza, Roma
  We use a generalization of the Twiss coefficients to the fully transverse coupled case. We show that the formalism is particularly useful to treat problems involving the beam optics of electrons propagating in undulators or solenoids. The method allows the treatment in analytical terms, we generalize the method including the effect of spatial charges and higher order multi-polar terms. The method is then applied to a specific example relevant to e-beam emittance dilution in solenoid and exotic undulators.  
 
WEPCH132 Design Study of Dedicated Computer System for Wake Field Analysis with Time Domain Boundary Element Method simulation, BNL, electron, controls 2233
 
  • K. Fujita, T. Enoto
    Hokkaido University, Sapporo
  • H. Kawaguchi
    Muroran Institute of Technology, Department of Electrical and Electronic Engineering, Muroran
  Time domain boundary element method (TDBEM) has advantages of dispersion free calculations and modeling of curved beam trajectories in wake field analysis compared to conventional methods. These advantages give us powerful possibilities for analysis of beam dynamics due to CSR in bunch compressors of next-generation accelerators. On the other hand, the TDBEM also has a serious difficulty of large computational costs. In this paper, a dedicated computer system for wake field analysis with the TDBEM is proposed as one of solutions for high performance computing (HPC) technologies. Recent remarkable progress of LSI hardware design environments such as HDL compiler tools and large scale FPGAs enables us to make up computer hardware systems with very low cost in a short development period. The authors have been working in design studies of the TDBEM dedicated computer system on such LSI design environments. This paper presents a system design and VHDL simulations of a wake field analysis machine based on the TDBEM.  
 
WEPCH144 CSR Effects in a Bunch Compressor: Influence of the Transverse Force and Shielding shielding, LEFT, simulation, radiation 2260
 
  • G. Bassi, J.A. Ellison, K.A. Heinemann
    UNM, Albuquerque, New Mexico
  We study the influence of CSR on particle bunches traveling on arbitrary planar orbits between parallel conducting plates with a fixed "vertical" charge distribution. Our goal is a numerical solution of the 2 degree-of-freedom Vlasov-Maxwell equations. This provides simulations with lower numerical noise than the macroparticle method and allows the study of emittance degradation and microbunching. As reported*, we calculate the fields excited by the bunch in the lab frame using a new formula that leads to a simplification. The Vlasov equation is integrated in the beam frame interaction picture using the method of local characteristics. The transformation between traditional beam frame and lab frame coordinates is carefully treated. Here we report on our implementation of the algorithm in the context of a chicane bunch compressor**, where the strong correlation between phase space variables requires an adaptive grid. In particular, we present a complete analysis (moments + reduced densities) of the bunch evolution under the fields produced by the unperturbed bunch density. Finally, our progress on the fully self-consistent case is discussed.

* Vlasov treatment of coherent synchrotron radiation from arbitrary planar orbits, Nucl. Instr. Meth. Phys. Res. A, in press.** ICFA Beam Dynamics Mini-Workshop on CSR, Berlin-Zeuthen, 2002. See http://www.desy.de/csr.

 
 
THOPA01 Formation of Electron Bunches for Harmonic Cascade X-ray Free Electron Lasers electron, linac, laser, radiation 2738
 
  • M. Cornacchia, S. Di Mitri, G. Penco
    ELETTRA, Basovizza, Trieste
  • A. Zholents
    LBNL, Berkeley, California
  A relatively long electron bunch is required for an operation of harmonic cascade free electron lasers (FELs). This is because they repeatedly employ a principle when the radiation produced in one cascade by one group of electrons proceeds ahead and interacts with other electrons from the same electron bunch in the next cascade. An optical laser is used to seed the radiation in the first cascade. Understandably the length of the electron bunch in this situation must accommodate the length of the x-ray pulse multiplied by a number of cascades plus a time jitter between the arrival time of the electron bunch and a seed laser pulse. Thus a variation of the peak current along the electron bunch as well as slice energy spread and emittance may affect the performance of the FEL. In this paper we analyze all possible sources affecting the distributions and interplay between them and show how desirable distributions can be produced. Results are illustrated with simulations using particle tracking codes.  
slides icon Transparencies
 
THPCH024 An Efficient Formalism for Simulating the Longitudinal Kick from Coherent Synchrotron Radiation space-charge, synchrotron, synchrotron-radiation, simulation 2829
 
  • D. Sagan
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  Coherent Synchrotron Radiation (CSR) can severely limit the performance of planned light sources and storage rings which push the envelope to ever higher bunch densities. In order to better simulate CSR, the formalism of Saldin is extended to work at lower energies and shorter length scales. The formalism is also generalized to cover the case of an arbitrary configuration of multiple bends.

*E. L. Saldin et al. Nucl. Instrum. Methods Phys. Res., Sect. A 398, 373 (1997).

 
 
THPCH064 Comparison of Three CSR Radiation Powers for Particle Bunches and Line Charges radiation, synchrotron, synchrotron-radiation, simulation 2931
 
  • K.A. Heinemann, G. Bassi, J.A. Ellison
    UNM, Albuquerque, New Mexico
  We are studying coherent synchrotron radiation (CSR) from arbitrary planar orbits as discussed in another abstract we submitted to EPAC06. It is important to have one-dimensional approximations. Here we report on work constructing and validating such approximations. As part of our work two well known papers by Saldin, Schneidmiller and Yurkov (SSY* are considered which deal with the CSR via a one-dimensional approximation whereby the electron bunch is modelled by a line density. Their one-dimensional approach is important because it is used in various CSR codes and since it serves to some extent as a role model for higher-dimensional models. The present report deals with some general aspects of the work of SSY. In particular, care is taken of the renormalization procedure and of the statistical description in terms of the line density. SSY use a renormalized retarded field whereas the present work uses the radiation field which is defined as half the difference of the retarded and advanced fields. The radiation field came into prominence when Dirac** introduced the Lorentz-Dirac equation.

*E. L. Saldin, et al. Nucl. Instr. Meth. Phys. Res. A 398, 373 (1997) and 417, 158 (1998).**P.A.M. Dirac, Proc. Roy. Soc. (London) A167, 148 (1938).

 
 
THPCH067 Coherent Synchrotron Radiation Studies at the Accelerator Test Facility injection, synchrotron, radiation, synchrotron-radiation 2940
 
  • S. De Santis, J.M. Byrd
    LBNL, Berkeley, California
  • A. Aryshev, T. Naito, J. Urakawa
    KEK, Ibaraki
  • M.C. Ross
    SLAC, Menlo Park, California
  Coherent Synchrotron Radiation (CSR) has been the object of recent experiments and is a topic of great importance for several accelerator currently in their design phase (LCLS, ILC, CIRCE). We present the results of several experimental sessions performed at the Advanced Test Facility - KEK (ATF). An infrared bolometer was used to detect the emitted infrared radiation in the 1-0.05 mm wavelength range as a function of several beam parameters (beam current, RF power, extraction timing, photoinjector laser phase). The beam energy spread was also recorded. We found that the mismatch between injected and equilibrium beam is the source of the coherent signal detected concurrently with the bunch injection.  
 
THPLS016 Bunch Shape Diagnostics Using Femtoslicing laser, electron, radiation, undulator 3305
 
  • K. Holldack, T. Quast
    BESSY GmbH, Berlin
  • S. Khan
    Uni HH, Hamburg
  • R. Mitzner
    Universität Muenster, Physikalisches Institut, Muenster
  Laser-energy modulation of relativistic electron bunches as needed for the BESSY femtosecond (fs) x-ray source is accompanied by the emission of fs THz pulses*. The total THz intensity probes the square of the longitudinal particle density within a slice of ~50 fs length (fwhm). The bunch shape can be directly monitored while sweeping the time delay between laser and bunch clock. The method is demonstrated for bunch lengths between 3 and 30 ps (rms) in different operation modes of BESSY II. The use of THz signals from successive turns and the influence of periodic bursts of coherent synchrotron radiation, which lock to the laser pulse under certain conditions, are discussed. The method is used for setting up and stabilizing the temporal overlap between a fs-laser and a relativistic electron bunch.

*K. Holldack et al., Phys. Rev. Lett. (2006), accepted Dec. 2005.

 
 
THPLS041 Observation of Intense Terahertz Synchrotron Radiation produced by Laser Bunch Slicing at UVSOR-II laser, electron, radiation, synchrotron 3377
 
  • M. Katoh, M. Hosaka, K. Kimura, A. Mochihashi, M. Shimada
    UVSOR, Okazaki
  • T. Hara
    RIKEN Spring-8 Harima, Hyogo
  • T. Takahashi
    KURRI, Osaka
  • Y. Takashima
    Nagoya University, Nagoya
  We have performed electron bunch slicing experiments using a femto-second high power pulse laser in the UVSOR-II electron storage ring. As the pulse laser system we have used a Ti:Sa laser whose wavelength is 800 nm, typical pulse duration is 100 fs, pulse repetition is 1 kHz and typical average power is 2W. The laser is operated in mode-locked condition and synchronized with the electron beam revolution. The laser pulse is injected into an undulator section and it goes along with the electron bunch. By adjusting the radiation wavelength of the undulator to the laser wavelength, the electron beam energy can be partially modulated in the electron bunch. We have observed THz synchrotron radiation (SR) light from a bending magnet that is downstream of the interaction region. The SR light contains extremely intense THz pulse radiation that is synchronized with the laser injection. The extremely high intensity strongly suggests that the THz pulses are coherent synchrotron radiation from the electron bunch with a hole because of the laser-beam interaction.  
 
THPLS042 Observation of THz Synchrotron Radiation Burst in UVSOR-II Electron Storage Ring radiation, synchrotron, electron, synchrotron-radiation 3380
 
  • A. Mochihashi, M. Hosaka, M. Katoh, K. Kimura, M. Shimada
    UVSOR, Okazaki
  • T. Takahashi
    KURRI, Osaka
  • Y. Takashima
    Nagoya University, Nagoya
  Very intense THz synchrotron radiation bursts have been observed in single-bunch operation in the UVSOR-II electron storage ring*. The observation was performed in an infrared beam line in UVSOR-II by using a liquid-He-cooled In-Sb hot-electron bolometer that has a good response time of several microseconds. Thanks both to the beam line and the detector, it is clearly observed that the intense bursts have typical macroscopic and microscopic temporal structure. Macroscopically, it is clearly observed that the bursts tend to be generated with quasi-periodic structure in which the period tends to depend on the beam intensity. From a microscopic point of view, each burst has also quasi-periodic structure in itself, and the period almost corresponds to the half value of the inverse of the synchrotron oscillation frequency. The peak intensity of the bursts was about 10000 times larger than that of ordinary synchrotron radiation in the same wavelength region. The extremely high intensity strongly suggests that the bursts are coherent synchrotron radiation, although the radiation wavelength was much shorter than the electron bunch length.

*Y. Takashima et al., Jpn. J. Appl. Phys. 44, No.35 (2005) L1131.

 
 
THPLS097 Model of the CSR Induced Bursts in Slicing Experiments laser, electron, undulator, SLAC 3502
 
  • G.V. Stupakov, S.A. Heifets
    SLAC, Menlo Park, California
  In a recent experiment on 'femtoslicing' at the Advanced Light Source in LBNL, it has been observed that the beam slicing initiates correlated bursts of coherent synchrotron radiation (CSR) of the beam. In this paper, we suggest a model describing such bursts. The model is based on the linear theory of the CSR instability in electron rings. We describe how an initial perturbation of the beam generated by the laser pulse evolves in time when the beam is unstable due to the CSR wakefield. Although this model does not give quantitative predictions, it qualitatively explains the evolution of the induced CSR bursts.