Beam Physics for FEL
Paper Title Page
MOICNO01 Generation of a Train of Short Pulses by Means of FEL Emission of a Combed Electron Beam 2
 
  • V. Petrillo
    Universita' degli Studi di Milano, Milano, Italy
  • M.P. Anania, M. Bellaveglia, E. Chiadroni, D. Di Giovenale, G. Di Pirro, M. Ferrario, G. Gatti, R. Pompili, C. Vaccarezza, F. Villa
    INFN/LNF, Frascati (Roma), Italy
  • M. Artioli
    ENEA-Bologna, Bologna, Italy
  • A. Bacci, A.R. Rossi
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • A. Cianchi
    Università di Roma II Tor Vergata, Roma, Italy
  • F. Ciocci, G. Dattoli, L. Giannessi, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • A. Mostacci
    Rome University La Sapienza, Roma, Italy
  • P. Musumeci
    UCLA, Los Angeles, California, USA
  • J.V. Rau
    ISM-CNR, Rome, Italy
 
  We present a direct and powerful method for generating train of radiation pulses based on the FEL radiation from a multi-peaked electron beam produced with a combed laser pulse accelerated and compressed in a linac by the velocity bunching technique. The electron beam, constituted by two bunches, can be extracted from the accelerating section when they are temporaly superimposed but separated in energy, so that each of them is characterized by a different value of the Lorentz factor. When driven in the FEL undulator, they emit two separate spectral lines, according to the FEL resonance condition, that interfere producing fringes in the time-domain. In this way a train of regular pulses can be obtained, without limitation in frequency, and with the perspective of reaching the attosecond domain in the X ray regime.  
slides icon Slides MOICNO01 [8.836 MB]  
 
MOICNO02
Control of Electron Beam Longitudinal Phase Space With a Novel Compact De-chirper for PAL-XFEL  
 
  • H.-S. Kang, M.S. Chae, T. Ha, J.H. Hong, W.W. Lee, S.J. Park, H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  The PAL-XFEL adopts a de-chirper system to remove the residual beam chirps with wakefield in corrugated pipes for the soft X-ray FEL line which is branched at 3 GeV point of the 10-GeV linac and does not have enough length of accelerating structures. The corrugated structure which is about 20 m long is designed to have the rectangular geometry and adjust the gap from 2 to 30 mm. We carried out the elegant code simulations using the wake formulas of G. Stupakov and K. Bane for the rectangular geometry to find the optimum parameters of corrugation using longitudinal wakes as well as to find the tolerance of vertical offset using transverse wakes. A 1-m long test de-chirper module is being designed and will be tested experimentally in July 2013 at the injector test facility in Pohang Accelerator Laboratory, which is a collaborative R&D with LBNL and SLAC.
Recommended by Zhirong Huang
 
slides icon Slides MOICNO02 [10.661 MB]  
 
MOOCNO01 Emittance Control in the Presence of Collective Effects in the FERMI@Elettra Free Electron Laser Linac Driver 6
 
  • S. Di Mitri, E. Allaria, D. Castronovo, M. Cornacchia, P. Craievich, M. Dal Forno, G. De Ninno, W.M. Fawley, E. Ferrari, L. Fröhlich, L. Giannessi, E. Karantzoulis, A.A. Lutman, G. Penco, C. Serpico, S. Spampinati, C. Spezzani, M. Trovò, M. Veronese
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • P. Craievich
    PSI, Villigen PSI, Switzerland
  • M. Dal Forno
    University of Trieste, Trieste, Italy
  • G. De Ninno, S. Spampinati
    University of Nova Gorica, Nova Gorica, Slovenia
  • E. Ferrari
    Università degli Studi di Trieste, Trieste, Italy
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • A.A. Lutman
    SLAC, Menlo Park, California, USA
 
  Recent beam transport experiments conducted on the the linac driving the FERMI@Elettra free electron laser have provided new insights concerning the transverse emittance degradation due to both coherent synchrotron radiation (CSR) and geometric transverse wakefield (GTW), together with methods to counteract such degradation. For beam charges of several 100's of pC, optics control in a magnetic compressor results to minimize the CSR once the H-function is considered*. We successfully extended this approach to the case of a modified double bend achromat system, opening the door to relatively large bending angles and compact transfer lines**. At the same time, the GTWs excited in few mm diameter iris collimators*** and accelerating structures have been characterized in terms of the induced emittance growth. A model integrating both CSR and GTW effects suggests that there is a limit on the maximum obtainable electron beam brightness in the presence of such collective effects.
* S. Di Mitri et al., PRST-AB 15, 020701 (2012)
** S. Di Mitri et al., PRL 110, 014801 (2013)
*** S. Di Mitri et al., PRST-AB 15, 061001 (2012)
 
slides icon Slides MOOCNO01 [6.919 MB]  
 
MOOCNO02 Multi-Objective Genetic Optimization for LCLS-II X-Ray FEL 12
 
  • L. Wang, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  The Linac Coherent Light Source II (LCLS-II) will build on the success of the world's most powerful X-ray laser, the Linac Coherent Light Source (LCLS). It will add two new X-ray laser beams and room for additional new instruments, greatly increasing the number of experiments carried out each year. Multiple operation modes are proposed to accommodate a variety of user requirements. There are a large number of variables and objectives in the design. For each operation mode, Multi-Objective Genetic Algorithm (MOGA) is applied to optimize the machine parameters in order to minimize the jitters, energy spread, collective effects and emittance. The optimal designs for various operation modes are presented in this paper. The phase and voltage of the linac RF, R56 at the two bunch compressors are optimized. The CSR (coherent synchrotron radiation) can induce large emittance growth, which is minimized by optimizing the phase advance between the compressor and the bend section. The final emittance at the beginning of the undulator is just about 1um and even lower.  
slides icon Slides MOOCNO02 [3.046 MB]  
 
MOOCNO03
Suppressing the Shot Noise in Charged Electron Beams at Short Wavelengths  
 
  • A. Gover, E. Dyunin, A. Nause
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • M.G. Fedurin
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work was supported in part by the Israel Science Foundation Grant No. 353/09
Shot noise in electron beam remains one of the features beyond control of accelerator physicist. Current results attained in experiment at ATF (BNL), published in Nature Physics, suggest that the control of the shot noise in electron beam in visible range of spectrum (and therefore spontaneous radiation) become a reality. Similar results had been obtained at SLAC. In this talk the authors will present experimental results of the experiments demonstration of the noise suppression and plans for next generation of the experiments. Possibility of extending of the noise suppression to shorter wavelength will be also discussed.
 
slides icon Slides MOOCNO03 [0.886 MB]  
 
MOOCNO04 Using a Lienard-Wiechert Solver to Study Coherent Synchrotron Radiation Effects 17
 
  • R.D. Ryne
    LBNL, Berkeley, California, USA
  • B.E. Carlsten, N.A. Yampolsky
    LANL, Los Alamos, New Mexico, USA
 
  We report on coherent synchrotron radiation (CSR) modeling using a new first-principles Lienard-Wiechert solver (CSR3D) that simulates real-world number of particles (624 million to 6.24 billion for 100-pC to 1-nC bunch charges). Using this tool, we have verified the limits of applicability of the common 1-D CSR model, including effect due to transverse beam size and shape. We also have observed energy dependent, wavelength dependent, and transverse-size dependent effects on CSR enhancement from microbunching. Additionally, we describe statistics of CSR shot noise, including dependencies on beam energy and transverse position and resulting energy diffusion. We consider the full transverse equation of motion and also quantify the effect of emittance growth from the bunch’s transverse radiation force.  
slides icon Slides MOOCNO04 [6.258 MB]  
 
MOPSO06 Paraxial Approximation in CSR Modeling Using the Discontinuous Galerkin Method 32
 
  • D. A. Bizzozero, J.A. Ellison, K.A. Heinemann, S.R. Lau
    UNM, Albuquerque, New Mexico, USA
 
  Funding: This work was primarily supported by DOE under DE-FG-99ER41104. The work of DB and SL was partially supported by NSF grant PHY 0855678 to the University of New Mexico.
We continue our study* of CSR from a bunch moving on an arbitrary curved trajectory. In that study we developed an accurate 2D CSR Vlasov-Maxwell code (VM3@A) and applied it to a four dipole chicane bunch compressor. Our starting point now is the well-established paraxial approximation** with boundary conditions for a perfectly conducting vacuum chamber with uniform cross-section. This is considerably different from our previous approach* where we calculated the fields from an integral over history, using parallel plate boundary conditions. In this study, we present a Discontinuous Galerkin (DG) method for the paraxial approximation equations. Our basic tool is a MATLAB DG code on a GPU using MATLAB's gpuArray; the code was developed by one of us (DB). We discuss our results in the context of previous work and outline future applications for DG, including a Vlasov-Maxwell study.
* See PRST-AB 12 080704 (2009) and Proceedings from ICAP2012 TUSDC2.
** See PRST-AB 7 054403 (2004), PRST-AB 12 104401 (2009) and Jpn. J. Appl. Phys. 51 016401 (2012).
 
 
MOPSO27 Study of CSR Effects in the Jefferson Laboratory FEL Driver 58
 
  • C.C. Hall, S. Biedron, T.A. Burleson, S.V. Milton, A.L. Morin
    CSU, Fort Collins, Colorado, USA
  • S.V. Benson, D. Douglas, P.E. Evtushenko, F.E. Hannon, R. Li, C. Tennant, S. Zhang
    JLAB, Newport News, Virginia, USA
  • B.E. Carlsten, J.W. Lewellen
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Work supported by the Office of Naval Research and the High Energy Laser Joint Technology. Jefferson Laboratory work also received supported under U.S. DOE Contract No. DE-AC05-06OR23177.
In a recent experiment conducted on the Jefferson Laboratory IR FEL driver the effects of Coherent Synchrotron Radiation (CSR) on beam quality were studied. The primary goal of this work was to explore CSR output and effect on the beam with variation of the bunch compression in the IR chicane. This experiment also provides a valuable opportunity to benchmark existing CSR models in a system that may not be fully represented by a 1-D CSR model. Here we present results from this experiment and compare to initial simulations of CSR in the magnetic compression chicane of the machine. Finally, we touch upon the possibility for CSR induced microbunching gain in the magnetic compression chicane, and show that parameters in the machine are such that it should be thoroughly damped.
 
 
MOPSO31 Quasiperiodic Method of Averaging Applied to Planar Undulator Motion Excited by a Fixed Traveling Wave 762
 
  • K.A. Heinemann, J.A. Ellison
    UNM, Albuquerque, New Mexico, USA
  • M. Vogt
    DESY, Hamburg, Germany
 
  Funding: The work of JAE and KH was supported by DOE under DE-FG-99ER41104. The work of MV was supported by DESY.
We present a mathematical analysis of planar motion of energetic electrons moving through a planar dipole undulator, excited by a fixed planar polarized plane wave Maxwell field in the X-Ray FEL regime.* We study the associated 6D Lorentz system as the wavelength of the traveling wave varies. The 6D system is reduced, without approximation, to a 2D system (for a scaled energy deviation and generalized ponderomotive phase) in a form for a rigorous asymptotic analysis using the Method of Averaging (MoA), a long time perturbation theory. As the wavelength varies the system passes through resonant and nonresonant (NR) zones and we develop NR and near-to-resonant (NtoR) normal form approximations. For a special initial condition, on resonance, we obtain the well-known FEL pendulum system. We prove NR and NtoR first-order averaging theorems, in a novel way, which give optimal error bounds for the approximations. The NR case is an example of quasiperiodic averaging where the small divisor problem enters in the simplest possible way. To our knowledge the analysis has not been done with the generality here nor has the standard FEL pendulum system been derived with error bounds.
* J.A. Ellison, K. Heinemann, M. Vogt, M. Gooden: arXiv:1303.5797 [physics.acc-ph]
 
 
MOPSO40 CLARA Accelerator Design and Simulations 72
 
  • P.H. Williams, D. Angal-Kalinin, J.A. Clarke, F. Jackson, J.K. Jones, B.P.M. Liggins, J.W. McKenzie, B.L. Militsyn
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Funding: Science & Technology Facilities Council
We present the accelerator design for CLARA (Compact Linear Advanced Research Accelerator) at Daresbury Laboratory. CLARA will be a testbed for novel FEL configurations. The accelerator will consist of an RF photoinjector, S-band acceleration and transport to 250MeV including X-band linearisation and magnetic bunch compression. We describe the transport in detail. Beam dynamics simulations are then used to define a set of operating working points suitable for the different FEL schemes intended to be tested on CLARA.
 
 
MOPSO57 Measurement of Wigner Distribution Function for Beam Characterization of FELs 92
 
  • T. Mey, K. Mann, B. Schäfer
    LLG, Goettingen, Germany
  • B. Keitel, S. Kreis, M. Kuhlmann, E. Plönjes, K.I. Tiedtke
    DESY, Hamburg, Germany
 
  Free-electron lasers deliver VUV and soft x-ray pulses with the highest brilliance available and high spatial coherence. Users of such facilities have high demands on phase and coherence properties of the beam, for instance when working with coherent diffractive imaging (CDI). To gain highly resolved spatial coherence information, we have performed a caustic scan at BL2 of FLASH using the ellipsoidal beam line focusing mirror and a movable XUV sensitive CCD detector. This measurement allows for retrieving the Wigner distribution function, being the two-dimensional Fourier transform of the mutual intensity of the beam. Computing the reconstruction on a four-dimensional grid, this yields the Wigner distribution which describes the beam propagation completely. Hence, we are able to provide comprehensive information about spatial coherence properties of the FLASH beam including the mutual coherence function and the global degree of coherence. Additionally, we derive the beam propagation parameters such as Rayleigh length, waist diameter and the beam quality factor M².  
 
MOPSO66 Start-to-end Simulation of a Next Generation Light Source Using the Real Number of Electrons 112
 
  • J. Qiang, J.N. Corlett, P. Emma, C.E. Mitchell, C. F. Papadopoulos, G. Penn, M.W. Reinsch, R.D. Ryne, M. Venturini
    LBNL, Berkeley, California, USA
  • S. Reiche
    PSI, Villigen PSI, Switzerland
 
  Funding: This research was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Start-to-end simulation plays an important role in design and optimization of next generation light sources. In this paper, we will present start-to-end (from the photocathode to the end of undulator) simulations of a high repetition rate FEL-based Next Generation Light Source driven by CW superconducting linac with the real number of electrons (~2 billion electrons/bunch) using the multi-physics parallel beam dynamics code IMPACT. We will discuss challenges, numerical methods and physical models used in the simulation. We will also present simulation results of a beam transporting through photoinjector, beam delivery system, and final X-ray FEL radiation.
 
 
MOPSO73 Suface Roughness Wakefield in FEL Undulator 127
 
  • G.V. Stupakov
    SLAC, Menlo Park, California, USA
  • S. Reiche
    PSI, Villigen PSI, Switzerland
 
  Among several wakefield models for the FEL undulator vacuum chamber a simple sinusoidal wall modulation with a small ratio of height to wavelength is especially attractive because of its simplicity [1]. The model neglects a so called resonant mode wakefield and has an (integrable) singularity at the origin which makes difficult its use in practical simulations. In this work we generalize the longitudinal wake of a sinusoidally modulated wall to include the effect of the resonant mode. This also removes the singularity of the wake at the origin. The new wake is used to evaluate the roughness wakefield effect in the undulator of SwissFEL.
[1] G. Stupakov, in "Nonlinear and Collective Phenomena in Beam Physics 1998" Workshop, New York (1999), no. 468 in AIP Conference Proceedings, pp. 334–47.
 
 
MOPSO77 Timing Jitter Measurements of the SwissFEL Test Injector 140
 
  • C. Vicario, B. Beutner, M.C. Divall, C.P. Hauri, S. Hunziker, M.G. Kaiser, M. Luethi, M. Pedrozzi, T. Schietinger
    PSI, Villigen PSI, Switzerland
  • C.P. Hauri
    EPFL, Lausanne, Switzerland
 
  To reach nominal bunch compression and FEL performance of SwissFEL with stable beam conditions for the users, less than 40fs relative rms jitter is required from the injector. Phase noise measurement of the gun laser oscillator shows an exceptional 30fs integrated rms jitter. We present these measurements and analyze the contribution to the timing jitter and drift from the rest of the laser chain. These studies were performed at the SwissFEL injector test facility, using the rising edge of the Schottky-scan curve and on the laser system using fast digital signal analyzer and photodiode, revealing a residual jitter of 150fs at the cathode from the pulsed laser amplifier and beam transport, measured at 10Hz. Spectrally resolved cross-correlation technique will also be reviewed here as a future solution of measuring timing jitter at 100Hz directly against the pulsed optical timing link with an expected resolution in the order of 50fs. This device will provide the signal for feedback systems compensating for long term timing drift of the laser for the gun as well as for the pulsed lasers at the experimental stations.