Keyword: simulation
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MOOCNO02 Multi-Objective Genetic Optimization for LCLS-II X-Ray FEL emittance, undulator, linac, wakefield 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]  
 
MOOCNO04 Using a Lienard-Wiechert Solver to Study Coherent Synchrotron Radiation Effects radiation, undulator, electron, dipole 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]  
 
MOPSO02 Measurement of Electron-Beam and Seed Laser Properties Using an Energy Chirped Electron Beam electron, laser, FEL, linac 24
 
  • E. Allaria, G. De Ninno, S. Di Mitri, W.M. Fawley, E. Ferrari, L. Fröhlich, G. Penco, P. Sigalotti, S. Spampinati, C. Spezzani, M. Trovò
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • G. De Ninno, S. Spampinati
    University of Nova Gorica, Nova Gorica, Slovenia
  • E. Ferrari
    Università degli Studi di Trieste, Trieste, Italy
 
  We present a new method that uses CCD images of the FERMI electron beam at the dump spectrometer after the undulator to determine various electron beam and external seed laser properties. By taking advantage of the correlation between time and electron beam energy for a quasi-linearly chirped electron beam and the fact that the FERMI seed laser pulse (~180 fs) is much shorter than the electron beam duration (~1 ps), measurements of the e-beam pulse length and temporally local energy chirp and current are possible. Moreover, the scheme allows accurate determination of the timing jitter between the electron beam and the seed laser, as well as a measure of the latter's effective pulse length in the FEL undulators. The scheme can be also provide an independent measure of the energy transferred from the electron beam to the FEL output radiation. We describe the proposed method as well as some experimental results obtained at the seeded FERMI FEL.  
 
MOPSO06 Paraxial Approximation in CSR Modeling Using the Discontinuous Galerkin Method impedance, vacuum, radiation, synchrotron 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).
 
 
MOPSO08 Unaveraged Modelling of a LWFA Driven FEL FEL, electron, radiation, undulator 43
 
  • L.T. Campbell, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • F.J. Grüner, A.R. Maier
    CFEL, Hamburg, Germany
  • F.J. Grüner, A.R. Maier
    Uni HH, Hamburg, Germany
  • F.J. Grüner
    LMU, Garching, Germany
 
  Preliminary simulations of a Laser Wakefield Field Accelerator driven FEL are presented using the 3D unaveraged, broad bandwidth FEL simulation code Puffin. The radius of the matched low emittance electron beam suggests that the FEL interaction will be strongly affected by radiation diffraction. The parameter scaling and comparison between 3D and equivalent 1D simulations appears to confirm the interaction is diffraction dominated. Nevertheless, output powers are predicted to be greater than those of similar unaveraged FEL models. Possible reasons for the discrepancies between the averaged and unaveraged simulation results are discussed.
[1] - AR Maier, A Meseck, S Reiche, CB Schroeder, T Seggebrock, and F Gruner, Phys Rev X 2, 031019 (2012)
 
 
MOPSO27 Study of CSR Effects in the Jefferson Laboratory FEL Driver FEL, radiation, dipole, linac 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.
 
 
MOPSO40 CLARA Accelerator Design and Simulations linac, FEL, laser, emittance 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.
 
 
MOPSO44 Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns laser, cathode, electron, gun 79
 
  • J.M.D. Kowalczyk, M.R. Hadmack, J. Madey
    University of Hawaii, Honolulu, HI, USA
 
  Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03.
A theoretical study of the use of laser cooling to counteract electron back-bombardment heating (BB) in thermionic electron guns is presented. Electron beams with short bunches, minimum energy spread, and maximum length pulse trains are required for many applications, including the inverse-Compton X-ray source being developed at UH. Currently, these three electron beam parameters are limited by BB which causes the cathode temperature and emission current to increase leading to beam loading. Beam loading elongates the bunches by shifting the electrons’ relative phases, introduces energy spread by reducing the energy of electrons emitted later in the macropulse, and forces the use of shorter macropulses to minimize energy spread. Irradiation of the electron gun cathode with a short laser pulse prior to beam acceleration allows the laser heat to diffuse into the cathode bulk effectively cooling the surface and counteracting the BB. Calculation of the the cooling produced by laser pulses of various duration and energy is presented.
 
 
MOPSO49 Numerical Accuracy When Solving the FEL Equations FEL, electron, undulator, bunching 82
 
  • R.R. Lindberg
    ANL, Argonne, USA
 
  Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357
The usual method of numerically solving the FEL equations involves dividing both the e-beam and radiation field into "slices" that are loaded one at a time into memory. This scheme is only first order accurate in the discretization of the ponderomotive phase because having only one slice in memory effectively results in a first order interpolation of the field-particle coupling. While experience has shown that FEL simulations work quite well, the first order accuracy opens the door to two possible ways of speeding up simulation time. First, one can consider higher order algorithms; unfortunately, these methods appear to require all the particle and field data in memory at the same time, and therefore will typically only be important for either small (probably 1D) problems or for parallel simulations run on many processors. Second, one may consistently solving the equations to some low order using faster, simpler algorithms (replacing, for example, the usual RK4). The latter is particularly attractive, although in practice it may be desirable to retain higher order methods when integrating along z. We investigate some of the possibilities.
 
 
MOPSO51 Feasibility of an XUV FEL Oscillator at ASTA FEL, undulator, electron, cryomodule 88
 
  • A.H. Lumpkin
    Fermilab, Batavia, USA
  • H. Freund
    LANL, Los Alamos, New Mexico, USA
  • M.W. Reinsch
    LBNL, Berkeley, California, USA
 
  Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A significant opportunity exists at the Advanced Superconducting Test Accelerator (ASTA) facility presently under construction at Fermilab to enable the first XUV free electron laser (FEL) oscillator experiments. The ultrabright beam from the L-band photoinjector will provide sufficient gain to compensate for reduced mirror reflectances in the VUV-XUV regimes, the 3-MHz micropulse repetition rate for 1 ms will support an oscillator configuration, the SCRF linac will provide stable energy, and the eventual GeV-scale energy with three TESLA-type cryomodules will satisfy the FEL resonance condition in the XUV regime. Concepts based on combining such beams with a 5-cm-period undulator and optical resonator cavity for an FEL oscillator are described. We used the 68% reflectances for normal incidence on multilayer metal mirrors developed at LBNL*. Initial simulations using GINGER with an oscillator module and MEDUSA:OPC show saturation for the 13.4-nm case after 300 and 350 passes, respectively,of the 3000 pulses. Initially, VUV experiments could begin in the 180- to 120-nm regime using MgF2-coated Al mirrors with only one cryomodule installed and beam energies of 250-300 MeV.
*LBNL X-ray optics site: http://xdb.lbl.gov/Section4
 
 
MOPSO66 Start-to-end Simulation of a Next Generation Light Source Using the Real Number of Electrons electron, FEL, emittance, radiation 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.
 
 
MOPSO84 Numerical Investigations of Transverse Gradient Undulator Based Novel Light Sources FEL, electron, laser, undulator 152
 
  • T. Zhang, D. Wang, G.L. Wang, H.F. Yao
    SINAP, Shanghai, People's Republic of China
  • J.S. Liu, C. Wang, W.T. Wang, Z.N. Zeng
    Shanghai Institute of Optics and Fine Mechanics, Shanghai, People's Republic of China
  • J.Q. Wang, S.H. Wang
    IHEP, Beijing, People's Republic of China
 
  With the stat-of-the-art laser technique, the quality of electron beam generated from laser-plasma accelerator (LPA) is now becoming much more better. The natural merits LPA beam, e.g. high peak current, ultra-low emittance and ultra-short bunch length, etc., pave the way to the novel light sources, especially in the realm of developing much compact X-ray light sources, e.g. table-top X-ray free-electron laser, although the radiation power is limited by the rather larger energy spread than conventional LINAC. Luckily, much more power could be extracted by using the undulator with transverse gradient (TGU) when energy spread effect could be compensated. Here we introduce a novel soft x-ray light source driven by LPA based on TGU technique. Meanwhile we present a simple idea on how to achieve much higher rep-rate (e.g. ~100 kHz) storage ring based FELs boosted by TGU.  
 
TUOCNO01 Electron Beam Longitudinal Phase Space Manipulation by Means of an AD-HOC Photoinjector Laser Pulse Shaping electron, linac, FEL, laser 180
 
  • G. Penco, D. Castronovo, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, W.M. Fawley, L. Giannessi, C. Spezzani, M. Trovò
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
 
  In a seeded FEL machine as FERMI, the interplay between the electrons energy curvature and the seed laser frequency chirp has a relevant impact on the output FEL spectrum. It is therefore crucial controlling and manipulating the electron beam longitudinal phase space at the undulator entrance. In case of very short bunches, i.e. high compression scheme, the longitudinal wakefields generated in the linac induce a positive quadratic curvature in the electrons longitudinal phase space that is hard to compensate by tuning the phase of the main RF sections or the possible high harmonic cavity. At FERMI we have experimentally exploited a longitudinal ramp current distribution at the cathode, obtained with an ad-hoc photoinjector laser pulse shaping, to linearize the longitudinal wakefields in the downstream linac and flatten the electrons energy distribution, as theoretical foreseen in [1]. Longitudinal phase space measurements in this novel configuration are here presented, providing a comparison with the typical longitudinal flat-top profile.
[1] Phys. Rev. Special Topics - Accel. and Beams 9 (12), 120701 (2006)
 
slides icon Slides TUOCNO01 [28.792 MB]  
 
TUPSO03 Dark Current Transport and Collimation Studies for SwissFEL gun, emittance, wakefield, cathode 209
 
  • S. Bettoni, P. Craievich, M. Pedrozzi, S. Reiche, L. Stingelin
    PSI, Villigen PSI, Switzerland
 
  In all accelerating cavities a non negligible background of electrons can be generated by field emission (dark current), transported and further accelerated. A careful estimate of the transport of the dark current is crucial in order to minimize radiation damage to the components and activation of the machine. This paper describes the generation and the transport of dark current from the SwissFEL photo injector downstream of the accelerator. The analysis is based on numerical simulations and experimental measurements performed at the SwissFEL Injector Test Facility (SITF). In the simulations the charge distribution is generated by an emission model based on the Fowler-Nordheim equation taking into account the filling time of the cavity and then tracked through the machine. This model has been used to analyze the impact of a low energy collimation system upstream of the first travelling wave accelerating structure on the dark current transport. A slit with several apertures has been installed in the SITF to benchmark the simulations and to verify the impact of the wakefields on the nominal beam.  
 
TUPSO04 Simulations of a Corrugated Beam Pipe for the Chirp Compensation in SwissFEL wakefield, undulator, laser, emittance 214
 
  • S. Bettoni, P. Craievich, M. Pedrozzi, S. Reiche
    PSI, Villigen PSI, Switzerland
 
  In short wavelength FEL designs, bunch compression is obtained by making the beam passing through a magnetic chicane with an energy chirp typically of a percent level. At SwissFEL, before injection into the undulator it is foreseen to remove the residual chirp using the wakes in the C-band accelerating structures of the linac. This scheme works well for the hard X-ray undulator line, which includes the largest accumulation of wakefields, but it leaves a residual chirp in the other undulator line for the soft X-ray beam line, midway in the main linac. Another possibility to remove the residual chirp consists in using the longitudinal wakefields generated by a corrugated beam pipe, as recently proposed by G. Stupakov et al. Before planning a dechirper section in a FEL, an experimental verification of the analytical formulae describing the wakefields is crucial. The SwissFEL injector test facility (SITF) fulfils all the necessary criteria to perform such a proof of principle. We are investigating the technical implementation to perform an experiment in SITF in the second half of 2014. In this paper we present the tracking studies performed to optimize the experiment layout.  
 
TUPSO07 SwissFEL Injector Design: An Automatic Procedure emittance, gun, laser, space-charge 219
 
  • S. Bettoni, M. Pedrozzi, S. Reiche
    PSI, Villigen PSI, Switzerland
 
  The first section of photo-injectors are dominated by space charge effects due to the low beam energy and the high charge density. An optimization of several parameters such as the emittance and the mismatch along the bunch has to be carried out in order to optimize the final performances of the machine. We focus on the performances of the gun developed at PSI, planned to be installed in the mid of this year in the SwissFEL Injector Test Facility (SITF). Due to the number of variables and constraints we developed a code to automatically perform such an optimization. We used this code to optimize the 200 pC operating point of SwissFEL and to fine tune other charges configurations from 10 pC, obtaining considerably reduction of the slice emittance as compared to the CTF gun, presently installed in the SITF and on which the old lattice optimization was based. The same code with minor modifications has been successfully applied to the facility.  
 
TUPSO36 Beam Dynamics Optimization for the High Brightness PITZ Photo Injector Using 3D Ellipsoidal Cathode Laser Pulses laser, emittance, electron, cathode 298
 
  • M. Khojoyan, M. Krasilnikov, F. Stephan, G. Vashchenko
    DESY Zeuthen, Zeuthen, Germany
 
  Funding: The work is funded by the German Federal Ministry of education and Research, project 05K10CHE “Development and experimental test of a laser system for producing quasi 3D ellipsoidal laser pulses”.
The Photo Injector Test facility at DESY, Zeuthen Site (PITZ) is one of the leading producers of high brightness electron beams for linac based Free Electron Lasers (FELs) with a specific focus on the requirements of FLASH and the European XFEL. The main activities at PITZ are devoted to the detailed characterization and optimization of electron sources yielding to an extremely small transverse beam emittance. The cathode laser pulse shaping is considered as one of the key issues for the high brightness photo injector. Beam dynamics simulations show that the injector performance could be further improved by replacing the typical cylindrically shaped PITZ bunches by uniformly filled 3D ellipsoidal shaped electron beams. A set of numerical simulations were performed to study the beam dynamics of uniformly filled 3D ellipsoidal bunches with 1 nC charge in order to find an optimum PITZ machine setup which will yield the best transverse emittance. Simulation results comparing both options of cylindrical and 3D ellipsoidal beams are also presented and discussed.
 
 
TUPSO42 Shimming Strategy for the Phase Shifters Used in the European XFEL undulator, electron, laser, target 313
 
  • Y. Li, J. Pflüger, F. Wolff-Fabris
    XFEL. EU, Hamburg, Germany
  • H.H. Lu, Y.F. Yang
    IHEP, Beijing, People's Republic of China
 
  The undulator systems of the European XFEL need a total of 91 Phase Shifters. The 1st field integral of these devices must not exceed 0.004Tmm for working gaps > 16mm. For smaller gaps it is slightly released. In spite of the highly magnetically symmetric design and considerable effort such as the selection and sorting of the magnets small 1st field integral errors cannot be excluded. In this paper a strategy is studied to correct small gap dependent kicking errors as expected for the phase shifters of the XFEL. EU.by using shims of different geometries and sizes. It is found, that small gap dependent kicking errors can well be corrected for using this method. This is a systematic effort to provide effective fast tuning methods, which can be applied for the mass production. The meaning of shim signature will be explained in this paper. The method is demonstrated by simulations and measurements.  
 
TUPSO46 Analysis and Measurement of Focusing Effects in a Traveling Wave Linear Accelerator quadrupole, acceleration, focusing, electron 329
 
  • H. Maesaka, T. Asaka, H. Ego, T. Hara, T. Inagaki, Y. Otake, T. Sakurai, H. Tanaka, K. Togawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
 
  We propose a further precise model of the transverse dynamics in a traveling wave linear accelerator (TWA) and report experimental results to demonstrate the validity of the model. In SACLA, the beam orbit is calculated by using a transfer matrix based on the transverse dynamics model of each component and the matrix is utilized for orbit stabilization, beam envelop matching etc. For the TWA part, a transfer matrix including an emittance damping effect and an edge focusing effect [*] is employed. However, the beam orbit measured by rf cavity beam position monitors (RF-BPM) [**] did not agree with the calculated orbit, especially for the off-crest acceleration part. Therefore, focusing effects in a TWA structure were analyzed by using a 3-dimensional rf simulation code. The analysis indicated that the transverse dynamics model of the TWA should include an additional quadrupole edge focusing effect. The amount of the additional focusing effect of the TWA was measured in SACLA and the rf simulation result was confirmed to be consistent with the measurement. After the modification of the transverse dynamics model, the beam orbit measured by RF-BPM agrees with the calculation.
* T. Hara et al., Nucl. Instrum. Methods A 624, 65 (2010).
** H. Maesaka et al., Nucl. Instrum. Methods A 696, 66 (2012).
 
 
TUPSO67 Design Optimization of 100 Kv DC Gun Wehnelt Electrode for FEL Linac at LEBRA electron, gun, cathode, extraction 387
 
  • T. Sakai, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka
    LEBRA, Funabashi, Japan
 
  The 125-MeV electron linac at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been used for generation of the near infrared FEL and the Parametric X-ray Radiation. In addition, the THz beam generated in a bending magnet became available in the FEL experimental rooms in 2012 by transporting in the FEL optical beam line. The electron gun system for the LEBRA linac can extract the electron beam in three modes, the full bunch, the superimposed and the burst modes. However, the shape of the electron gun wehnelt electrode has not been optimized for the operation with the superimposed or the burst modes; the wehnelt was designed for use in the full bunch operation. The beam trace simulation suggested that the beam extracted from the cathode in the superimposed and the burst modes was slightly lost at the anode due to the strong space charge effect resulted from a high peak extraction current. Therefore, simulation of the beam trace was carried out to optimize the wehnelt shape for the maximum beam extraction efficiency for all the beam operation modes. The present paper reports the result of the simulation on the optimized electron gun design.  
 
TUPSO69 Injector Design Studies for NGLS gun, emittance, electron, cathode 391
 
  • C. F. Papadopoulos, P. Emma, D. Filippetto, H.J. Qian, F. Sannibale, M. Venturini, R.P. Wells
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The APEX project at LBNL is developing an electron injector to operate a high repetition rate x-ray FEL. The injector is based on the VHF gun, a high-brightness, high-repetition-rate photocathode electron gun presently under test at LBNL. The design of the injector is particularly critical because it has to take the relatively low energy beam from the VHF gun, accelerate it at more relativistic energies while simultaneously preserving high-brightness and performing longitudinal compression. The present status of the APEX injector design studies is presented.
 
 
TUPSO74 A Coaxially Coupled Deflecting-accelerating Mode Cavity System for Phase-space Exchange (PSEX) cavity, coupling, emittance, electron 395
 
  • Y.-M. Shin, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • M.D. Church
    Fermilab, Batavia, USA
  • J.H. Park, A.M.M. Todd
    AES, Princeton, New Jersey, USA
 
  A feasible method to readily remove energy spread (R56 term) due to thick lens effect of a deflecting mode RF-cavity has been widely investigated for emittance exchange in 6D phase-space*,**. By means of theoretical calculation and numerical analysis, it was found that an accelerating cavity effectively cancel the longitudinal phase space chirp. We have extensively investigated the combined deflecting-accelerating mode phase-space exchanger with the simple RF distribution system of the beam-pipe coaxial coupler. EM simulations proved the coupling scheme with eigenmode and S-parameter analyses. Currently we are looking into 3D beam dynamics in the system with tracking/particle-in-cell (PIC) simulations and wakefield analysis. Proof-of-concept (POC) experiment is planned with a high-Q normal conducting cavity built in a cryogenic cooling system (liquid nitrogen) in Fermilab.
* P. Emma, et. al., Phys. Rev. ST Accel. Beams 9, 100702 (2006)
** Zholents and M. Zolotorev, LBNL CBP Seminar (2010) and No. ANL/APS/LS-327(2011)
 
 
TUPSO75 Design Analysis and High Power RF Test of a 3.9 GHz 5-cell Deflecting-mode Cavity in a Cryogenic Operation cavity, vacuum, cryomodule, coupling 399
 
  • Y.-M. Shin
    Northern Illinois University, DeKalb, Illinois, USA
  • M.D. Church
    Fermilab, Batavia, USA
 
  A 3.9 GHz deflecting mode (π, TM110) cavity has been long used for six-dimensional phase-space beam manipulation tests [1 - 5] at the A0 Photo-Injector Lab (16 MeV) in Fermilab and their extended applications with vacuum cryomodules are currently planned at the Advanced Superconducting Test Accelerator (ASTA) user facility (> 50 MeV). Despite the successful test results, the cavity, however, demonstrated limited RF performance during liquid nitrogen (LN2) ambient operation that was inferior to theoretical prediction. We have been performing full analysis of the designed cavity by analytic calculation and comprehensive system simulation analysis to solve complex thermodynamics and mechanical stresses. The re-assembled cryomodule is currently under the test with a 50 kW klystron at the Fermilab A0 beamline, which will benchmark the modeling analysis. The test result will be used to design vacuum cryomodules for the 3.9 GHz deflecting mode cavity that will be employed at the ASTA facility for beam diagnostics and phase-space control.
[1] D. A. Edwards, LINAC 2002
[2] Y.-E Sun, PRTAB 2004
[3] P. Piot, PRSTAB2006
[4] J. Ruand et al., PRL 2011
[5] Y.-E. Sun, et al., PRL 2010
 
 
TUPSO77 Analytical and Numerical Analysis of Electron Trajectories in a 3-D Undulator Magnetic Field undulator, electron, focusing, radiation 406
 
  • N.V. Smolyakov, S.I. Tomin
    NRC, Moscow, Russia
  • G. Geloni
    XFEL. EU, Hamburg, Germany
 
  In this contribution we present an analysis of electron trajectories in the three dimensional magnetic field from a planar undulator. The electron trajectory is influenced by the focusing properties of the undulator field. These focusing properties should be taken into account in simulations of spontaneous radiation, which constitutes the background signal of the FEL. The ideal magnetic field of an undulator can be described, in agreement with Maxwell equations, by a sinusoidal vertical magnetic field on the undulator axis, and by horizontal and longitudinal field components that appear out of axis. Exploiting this description for the ideal case, the differential equations of motion were solved by means of a perturbation theory approach, and the corresponding expressions for the electrons velocities and trajectories are derived. A computer code was also written, which relies on the Runge-Kutta algorithm. The analytical and numerical methods could then be compared, showing a good agreement.  
 
TUPSO80 The MAX IV Linac and First Design for an Upgrade to 5 GeV to Drive an X-ray FEL linac, FEL, electron, storage-ring 413
 
  • S. Thorin, F. Curbis, N. Čutić, M. Eriksson, O. Karlberg, F. Lindau, A.W.L. Mak, E. Mansten, S. Werin
    MAX-lab, Lund, Sweden
 
  The installation of the MAX IV linear accelerator is in full progress, and commissioning is planned to start in the second quarter of 2014. The 3 GeV linac will be used as a full energy injector for the two storage rings, and as a high brightness driver for a Short Pulse linac light source. The linac has been deigned to also handle the high demands of an FEL injector. The long term strategic plan for the MAX IV laboratory includes an extension of the linac to 5 GeV and an X-ray FEL. In this paper we present the both design concept and status of the MAX IV linac along with parameters of the 3 GeV high quality electron pulses. We also present the first design and simulation results of the upgrade to a 5 GeV X-ray FEL driver.  
 
WEOBNO03 Intense Emission of Smith-Purcell Radiation at the Fundamental Frequency from a Grating Equipped with Sidewalls radiation, electron, bunching, solenoid 477
 
  • J.T. Donohue
    CENBG, Gradignan, France
  • J. Gardelle, P. Modin
    CEA, LE BARP cedex, France
 
  The two-dimensional theory of the Smith-Purcell free-electron laser predicts that coherent Smith-Purcell radiation can occur only at harmonics of the frequency of the evanescent wave that is resonant with the beam. Particle-in-cell simulations have shown that in a three-dimensional context, where the lamellar grating has sidewalls, coherent Smith-Purcell radiation can be copiously emitted at the fundamental frequency, for a well-defined range of beam energy. An experiment at microwave frequencies has confirmed this prediction . The power output is considerably greater than for the previously observed emission at the second harmonic, in agreement with three-dimensional simulations . The dependence of frequency on beam energy and emission angle is in good agreement with three-dimensional theory and simulations. Provided that a reduction in scale can be achieved, a path is open to coherent Smith-Purcell radiation at Terahertz frequencies.
(1) J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012).
(2) J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011).
 
slides icon Slides WEOBNO03 [11.891 MB]  
 
WEPSO14 Towards High Frequency Operation with a Multi-Grating Smith-Purcell FEL radiation, electron, FEL, bunching 525
 
  • J.T. Donohue
    CENBG, Gradignan, France
  • J. Gardelle
    CEA, LE BARP cedex, France
 
  Three-dimensional simulations and experiments have shown that, for a grating equipped with sidewalls, copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave is possible 1, 2. Since the underlying theory is scale invariant, the wavelength emitted is reduced in proportion to a uniform rescaling of the grating. In order to increase our 5 GHz to 100 GHz , the grating surface would be reduced by a factor of 400, which would lead to greatly reduced power. In addition, the required beam might be hard to generate. To avoid this, we propose to use several gratings in parallel with no overall reduction in the total width and the same beam as in our microwave experiment. For this scheme to succeed, it is essential that the bunching in the different gratings be coherent. . Simulations suggest that this occurs for as much as a ten-fold scale reduction. To test this idea, an experiment is using several gratings is being performed.
1. J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011).
2. J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012),.
 
 
WEPSO19 A Full Beam 1D Simulation Code for Modeling Hybrid HGHG/EEHG Seeding Schemes for Evaluating the Dependence of Bunching Factor Bandwidth on Multiple Parameters bunching, laser, FEL, electron 533
 
  • C.M. Fortgang, B.E. Carlsten, Q.R. Marksteiner, N.A. Yampolsky
    LANL, Los Alamos, New Mexico, USA
 
  Multiple seeding schemes are available for design of narrow-band, short-wavelength FELs. Analysis of such schemes often focus on the amplitude of the final bunching factor b, and how far it is above shot noise. Only under ideal conditions is the bandwidth of b FT limited. We have developed a 1D simulation tool that models complex hybrid seeding schemes using macro properties of the entire beam bunch to assess effects on both the amplitude and bandwidth of b. In particular the effects on bunching factor from using non-ideal beam driven radiators for downstream modulators, energy slew and curvature, and energy spread are investigated with the 1D tool.  
 
WEPSO44 Design Studies for FLUTE, A Linac-based Source of Terahertz Radiation radiation, laser, gun, linac 598
 
  • S. Naknaimueang, V. Judin, S. Marsching, A.-S. Müller, M.J. Nasse, R. Rossmanith, R. Ruprecht, M. Schreck, M. Schuh, M. Schwarz, M. Weber, P. Wesolowski
    KIT, Karlsruhe, Germany
  • W. Hillert, M. Schedler
    ELSA, Bonn, Germany
 
  FLUTE is a linac-based THz source with nominal beam energy of 40-50 MeV which is presently under construction at KIT. It will be operated in a wide bunch charge range and will use different electron bunch compression schemes. The source will also study different mechanisms of radiation generation and serve as a test facility for related accelerator technology. This contribution presents the results of an overall optimization of the accelerator and a bunch compressor. A usage of a dispersive compressor and a velocity buncher, as well as combination of both are discussed. It is shown that bunch lengths in the range of a few femtoseconds can be achieved at very low bunch charges, while nC-bunches can be compressed down to approximately 200 fs. The utilization of both schemes results in high THz radiation fields at the experimental port.  
 
WEPSO47 Simulation Results of Self-seeding Scheme in PAL-XFEL radiation, undulator, electron, emittance 606
 
  • Y.W. Parc, J.H. Han, I. Hwang, H.-S. Kang
    PAL, Pohang, Kyungbuk, Republic of Korea
  • I.S. Ko
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • J. Wu
    SLAC, Menlo Park, California, USA
 
  There are two major undulator lines in Pohang Accelerator Laboratory XFEL (PAL XFEL), soft X-ray and hard X-ray. For the hard X-ray undulator line, self-seeding is the most promising approach to supply narrow bandwidth radiation to the users. The electron energy at hard X-ray undulator is 10 GeV and the central wavelength is 0.1 nm. We plan to provide the self-seeding option in the Phase I operation of PAL-XFEL. In this talk, the simulation results for the self-seeding scheme of hard X-ray undulator line in PAL XFEL will be presented.  
 
WEPSO48 Simulation Studies of FELs for a Next Generation Light Source undulator, FEL, electron, photon 609
 
  • G. Penn, P. Emma, G. Marcus, J. Qiang, M.W. Reinsch
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Several possible FEL beamlines for a Next Generation Light Source are studied. These beamlines collectively cover a wide range of photon energies and pulse lengths. Microbunching and transverse offsets within the electron beam, generated through the linac, have the potential to significantly impact the longitudinal and transverse coherence of the x-ray pulses. We evaluate these effects and set tolerances on beam properties required to obtain the desired properties of the x-ray pulses.
 
 
WEPSO51 Self-seeding Design for SwissFEL FEL, undulator, electron, radiation 618
 
  • E. Prat, S. Reiche
    PSI, Villigen PSI, Switzerland
 
  The SwissFEL facility, planned at the Paul Scherrer Institute, will provide SASE and self-seeded FEL radiation at a hard (1-7 Å) and soft (7-70 Å) X-ray FEL beamlines. This paper presents the current status of the self-seeding design for SwissFEL. The layout and full 6D start-to-end simulation results are presented for the hard X-ray beamline. Studies for different charges and optimization of the first and second undulator stages are shown.  
 
WEPSO53 Harmonic Lasing at the LCLS electron, FEL, radiation, undulator 623
 
  • D.F. Ratner, Z. Huang, P.A. Montanez
    SLAC, Menlo Park, California, USA
  • E. Allaria
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • W.M. Fawley, L.N. Rodes
    LBNL, Berkeley, California, USA
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  Funding: Department of Energy
The LCLS beamlines deliver X-rays to users at photon energies up to 24 keV. With the fundamental wavelength limited to around 10 keV, there is user interest in the third harmonic, which can reach a few percent of the total beam power. McNeil et al* and Schneidmiller and Yurkov** have showed that introducing phase shifts or attenuators into the undulator line can increase harmonic power by driving lasing at the third harmonic. With the development of self-seeding chicanes, LCLS is now in position for a proof-of-principle experiment. Here we present simulations and plans for an experimental test following commissioning of the Soft X-ray Self-Seeding system.
*B.W.J. McNeil, G.R.M. Robb, M.W. Poole and N.R. Thompson, Phys. Rev. Lett., 96 084801 (2006)
**E. Schneidmiller and M. Yurkov, PR-STAB, 14 080702 (2012)
 
 
WEPSO56 Optical Design and Time-dependent Wavefront Propagation Simulation for a Hard X-Ray Split- and delay-unit for the European XFEL photon, FEL, instrumentation, undulator 627
 
  • S. Roling, B. Siemer, F. Wahlert, M. Wöstmann, H. Zacharias
    Universität Muenster, Physikalisches Institut, Muenster, Germany
  • S. Braun, P. Gawlitza
    Fraunhofer IWS, Dresden, Germany
  • O.V. Chubar
    BNL, Upton, Long Island, New York, USA
  • L. Samoylova, H. Sinn
    XFEL. EU, Hamburg, Germany
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  • F. Siewert
    HZB, Berlin, Germany
  • E. Ziegler
    ESRF, Grenoble, France
 
  For the European XFEL an x-ray split- and delay-unit (SDU) is built covering photon energies from 5 keV up to 20 keV. This SDU will enable time-resolved x-ray pump / x-ray probe experiments as well as sequential diffractive imaging on a femtosecond to picosecond time scale. The wavefront of the x-ray FEL pulses will be split by an edge of a silicon mirror coated with Mo/B4C and W/B4C multilayers. Both partial beams will then pass variable delay lines. For different wavelengths the angle of incidence onto the multilayer mirrors will be adjusted in order to match the Bragg condition. Hence, maximum delays between ± 2.5 ps at hν = 20 keV and up to ± 33 ps at hν = 5 keV will be possible. The time-dependent wave-optics simulations have been done with SRW software, for the fundamental and the 3rd harmonic. The XFEL radiation was simulated both in the Gaussian approximation as well as using an output of time-dependent SASE code FAST. Main features of the optical layout, including diffraction on the splitter edge, and optics imperfections were taken into account. Impact of these effects on the possibility to characterize spatial-temporal properties of FEL pulses are analyzed.  
 
WEPSO59 A Possible Upgrade of FLASH for Harmonic Lasing Down to 1.3 nm undulator, FEL, electron, radiation 646
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  We propose the 3rd harmonic lasing in a new FLASH undulator as a way to produce intense, narrow-band, and stable SASE radiation down to 1.3 nm with the present accelerator energy of 1.25 GeV. To provide optimal conditions for harmonic lasing, we suggest to suppress the fundamental with the help of a special set of phase shifters. We rely on the standard technology of gap-tunable planar hybrid undulators, and choose the period of 2.3 cm and the minimum gap of 0.9 cm; total length of the undulator system is 34.5 m. We demonstrate that the 3rd harmonic lasing at 1.3 nm provides peak power at a gigawatt level and the narrow intrinsic bandwidth, 0.1% (FWHM). Pulse duration can be controlled in the range of a few tens of femtoseconds, and the peak brilliance reaches the value of 1031 photons/(s  mrad2  mm2  0.1%  BW). With the given undulator design, a standard option of lasing at the fundamental wavelength to saturation is possible through the entire water window and at longer wavelengths. In this paper we briefly consider additional options such as polarization control, bandwidth reduction, self-seeding, X-ray pulse compression, and two-color operation.  
 
WEPSO63 Extension of SASE Bandwidth up to 2 % as a Way to Increase Number of Indexed Images for Protein Structure Determination by Femtosecond X-Ray Nanocrystallography at the European XFEL radiation, electron, undulator, photon 661
 
  • S. Serkez, V. Kocharyan, E. Saldin, I. Zagorodnov
    DESY, Hamburg, Germany
  • G. Geloni
    XFEL. EU, Hamburg, Germany
  • O. Yefanov
    CFEL, Hamburg, Germany
 
  Experiments at the LCLS confirmed the feasibility of femtosecond nanocrystallography for protein structure determination at near-atomic resolution. These experiments rely on X-ray SASE pulses with a few microradians angular spread, and about 0.2 % bandwidth. By indexing individual patterns and then summing all counts in all partial reflections for each index it is possible to extract the square modulus of the structure factor. The number of indexed images and the SASE bandwidth are linked, as an increasing number of Bragg spots per individual image requires an increasing spectral bandwidth. This calls for a few percent SASE bandwidth. Based on start-to-end simulations of the European XFEL baseline, we demonstrate that it is possible to achieve up to a 10-fold increase of the electron energy chirp by strongly compressing a 0.25 nC electron bunch. This allows for data collection with a 2 % SASE bandwidth, a few mJ radiation pulse energy and a few fs-pulse duration, which would increase the efficiency of protein determination at the European XFEL. We prove this concept with simulations of photosystem-I nanocrystals, with a size of about 300 nm.  
 
WEPSO78 Harmonic Lasing Self-seeded FEL undulator, FEL, electron, resonance 700
 
  • M.V. Yurkov, E. Schneidmiller
    DESY, Hamburg, Germany
 
  In this paper we perform analysis of capabilities of SASE FELs at the European XFEL for generation of narrow band radiation. An approach based on application of harmonic lasing self-seeding (HLSS) is under study[*]. Effective harmonic lasing occurs in the exponential gain regime in the first part of the undulator, making sure that the fundamental frequency is well below saturation. In the second part of the undulator the value of undulator parameter is reduced such that now the fundamental mode is resonant to the wavelength, previously amplified as the harmonic. The amplification process proceeds in the fundamental mode up to saturation. In this case the bandwidth is defined by the harmonic lasing (i.e. it is reduced by a significant factor depending on harmonic number) but the saturation power is still as high as in the reference case of lasing at the fundamental, i.e. brilliance increases. Application of the undulator tapering in the deep nonlinear regime would allow to generate higher peak powers approaching TW level.
* E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST-AB 15, 080702 (2012)