Keyword: simulation
Paper Title Other Keywords Page
MOP001 Particle Tracking Simulations for EXFEL Complex shape Collimators electron, radiation, lattice, photon 22
 
  • V.G. Khachatryan, V.H. Petrosyan, T.L. Vardanyan
    CANDLE SRI, Yerevan, Armenia
  
  The study sets the objective to investigate through numerical simulation the produced secondary radiation properties when the electron beam particles hit collimator walls. Using particle tracking simulation code FLUKA, the European XFEL electron beam as well as beam halo interaction with the collimator were simulated. The complex geometrical shape and material composition of the collimator have been taken into account. Absorbed dose spatial distribution in the material of the collimators and particle fluencies from the downstream surface of the collimator were simulated for the total secondary radiation and its main components.  
 
MOP007 High Accuracy Shimming Technique for the Phase Shifters of the European XFEL undulator, operation, permanent-magnet, electron 29
 
  • Y. Li
    DESY, Hamburg, Germany
  • J. Pflüger
    XFEL. EU, Hamburg, Germany
  
  For the European XFEL 91 phase shifters are needed, which have to fulfil stringent field integral specifications: There should be no observable beam deflection when the strength, i.e. the magnetic gap is changed In order to facilitate the mass production of 91 phase shifters within the tough XFEL schedule a shimming technique was developed. It is based on measured shim signatures and is straight forward and fast to apply. The method is described and results are presented demonstrating that all requirements can be fulfilled.  
 
MOP018 Conceptual Study of a Self-seeding Scheme at FLASH2 undulator, FEL, electron, photon 53
 
  • T. Plath, L.L. Lazzarino
    Uni HH, Hamburg, Germany
  • K.E. Hacker
    DELTA, Dortmund, Germany
  
  Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K1GU4 and 05K10PE1 and the German Research Foundation program graduate school 1355.
We present a conceptual study of a self-seeding installation at the new FEL beamline, FLASH2, at the free-electron laser at DESY, Hamburg. For self-seeding, light from a first set of undulators is filtered by a monochromator and thus acts as a seed for the gain process in the main undulator. This scheme has been tested at LCLS at SLAC with a diamond monochromator for hard X-rays and with a grating monochromator for soft X-rays covering energies between 700 and 1000 eV. For such a design to offer benefits at FLASH2, it must be modified to work with X-rays with wavelength of about 5 nm (248 eV) where the damage threshold of the monochromator in the setup and the divergence at longer wavelengths become an issue. An analysis of the potential performance and limitations of this setup is performed using GENESIS 1.3 and a method developed for the soft X-ray self-seeding experiment at the European XFEL. With a total of 9 undulators in the first stage and 8 undulators after the monochromator, a pulse energy contrast ratio of 4.5 was simulated with an initial peak current of 2.5 kA. 		 
 
MOP030 Performance Analysis of Variable-Period Helical Undulator with Permanent Magnet for a KAERI THz FEL undulator, permanent-magnet, FEL, radiation 84
 
  • J. Mun, K.H. Jang, Y.U. Jeong, K. Lee, S. H. Park, N. Vinokurov
    KAERI, Daejon, Republic of Korea
  • M.Y. Jeon
    Chungnam National University, Daejoen, Republic of Korea
  
  Funding: This work was supported by the World Class Institute Program of the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT and Future Planning.(NRF Grant Number:WCI2011-001)
We realized a variable-period permanent-magnet helical undulator with high (~1 T) field amplitude, which is almost constant over undulator periods of 23–26 mm. Each undulator period has 4 modular sections of iron poles and permanent magnets embedded in non-magnetic disks with holes along the undulator axis. Modular plates undergo a longitudinal repulsive force from the magnetic field pressure and the spring coils between modular plates. The undulator period can thus be controlled by mechanically changing of the end plate longitudinal position. This compact design is suitable for a table-top terahertz free electron lasers. The measured on-axis field is about 0.97 T with the deviation less than 1% through the whole range of the undulator period variation. The measured spread of the longitudinal coordinates of the undulator field component maxima is less than 1%, and the measured field distribution meets the requirement for our terahertz FEL. The field reproducibility was checked by six measurements of the undulator field after the period variation for the 26 mm period. The r. m. s. phase errors is 3.7 degrees. 		 
 
MOP037 Modeling and Design of the Variable Period and Pole Number Undulator for the Second Stage of the Novosibirsk FEL undulator, FEL, permanent-magnet, electron 96
 
  • I. Davidyuk
    NSU, Novosibirsk, Russia
  • O.A. Shevchenko, V.G. Tcheskidov, N. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  • N. Vinokurov
    KAERI, Daejon, Republic of Korea
  
  The concept of the permanent magnet variable period undulator (VPU) has been proposed just several years ago and there are few examples of its implementation yet. The VPUs have several advantages compared to conventional undulators. One of them is wider radiation wavelength tunability range and another one is an option to increase the number of poles for shorter periods. Both these advantages will be realized in VPU which is being developed now at Budker INP. In this paper we present the 2-D and 3-D magnetic field simulation results and discuss the design features of this VPU.  
 
MOP044 A Stripline Kicker Driver for the Next Generation Light Source kicker, high-voltage, coupling, hardware 121
 
  • F.M. Niell, N. Butler, M.P.J. Gaudreau, M.K. Kempkes
    Diversified Technologies, Inc., Bedford, Massachusetts, USA
  
  Funding: DOE Contract DE-SC0004255
Diversified Technologies, Inc. (DTI), under an SBIR grant from the U.S. Department of Energy, assembled a prototype MOSFET-based pulse generator capable of meeting the original specifications for the Next Generation Light Source (NGLS) fast deflector. This pulse generator is also applicable to other high repetition-rate FELs with multiplexed beamlines. The unit must drive a 50 Ω load (such as a terminated TEM deflecting structure) at 10 kV, with flat-topped pulses at a 100 kHz average rate. The specification requires a 2 ns rise time (10 – 90%), a highly repeatable flattop with pulse width from 5 – 40 ns, and a fall time (90% to .01%) less than 1 μs (to allow a 1 MHz beam pulse rate). The driver must also effectively absorb high-order mode signals emerging from the deflector itself. The solid-state pulse generator is suitable for many accelerator systems with < 10 ns kicker requirements. The performance and applications of the unit will be described. 		 
 
MOP045 Phase Shifter Design for iSASE electron, power-supply, undulator, FEL 123
 
  • S.D. Chen, K. Fang, H.-D. Nuhn, C. Pellegrini, J. Wu, L. Zhu
    SLAC, Menlo Park, California, USA
  • S.D. Chen, C.-S. Hwang
    NCTU, Hsinchu, Taiwan
  • K. Fang
    Indiana University, Bloomington, Indiana, USA
  • C.-S. Hwang
    NSRRC, Hsinchu, Taiwan
  
  A phase shifter to generate an additional phase advance of the spontaneous light versus the electron beam was de- signed for the iSASE scheme. The iSASE mechanism is for reducing the bandwidth further from SASE FEL process. A large phase advance about 1600*2Pi as the FEL operating at wavelength 0.8 nm was needed according to the simulation of iSASE process. Since the iSASE is thought to implement into LCLS II project, the space limitation causing by LCLS II should be considered when designing the phase shifter. An optimized three-pole electric phase shifter with 7.3 mm gap has the center field of 1.8 T . The vanadium steel was considered as pole material and the magnet physical length is 260 mm, meanwhile the water-cooling type copper coil was adopted. The temperature increment, force analysis, low field operation mode concept, and preliminary tolerance study were discussed.  
 
MOP052 Update on FEL Performance for SwissFEL FEL, undulator, radiation, emittance 140
 
  • E. Prat, S. Reiche
    PSI, Villigen PSI, Switzerland
  
  The SwissFEL project under construction at the Paul Scherrer Institute foresees for 2017 the realization of an X-ray FEL with a photon wavelength down to 1 Å. In this paper we present the expected SASE performance for SwissFEL based on input distributions obtained from detailed start-to-end simulation results. The effects of the longitudinal wakefields due to resistive wall and surface roughness in the undulator beamline have been taken into account. We have studied and optimized the impact on the FEL performance of different factors like the electron focusing or the undulator tapering. Results for the standard cases with 200 pC and 10 pC electron bunch charge are shown.  
 
MOP053 SASE FEL Performance at the SwissFEL Injector Test Facility FEL, undulator, electron, gun 144
 
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  
  A 4 m long prototype of the SwissFEL undulator module with an undulator period length of 15 mm was installed at the SwissFEL Injector Test Facility and tested with a 200 MeV electron beam in the beginning of 2014. We observed FEL lasing in SASE mode in the wavelength range from 70 to 800 nm, tuning the wavelength by energy and gap. The measurements of the FEL performance are reported.
on behalf of the SwissFEL Team 		 
 
MOP055 Start-to-End Simulations for IR/THz Undulator Radiation at PITZ electron, radiation, undulator, FEL 153
 
  • P. Boonpornprasert, M. Khojoyan, M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • B. Marchetti, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  • S. Rimjaem
    Chiang Mai University, Chiang Mai, Thailand
  
  High brightness electron sources for modern linac-based Free-Electron Lasers (FELs) have been characterized and optimized at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). Since the time structure of the electron bunches at PITZ is identical to those at the European XFEL, the PITZ accelerator is being considered as a proper machine for the development of an IR/THz source prototype for pump and probe experiments planned at the European XFEL. Tunable IR/THz radiation sources using synchrotron radiation from a dipole magnet, transition radiation, high gain FELs and coherent radiation of tailored or premodulated beams are currently under consideration. This work describes start-to-end simulations for generating the FEL radiation using an APPLE-II undulator with electron beams produced by the PITZ accelerator. Analysis of the physical parameter space has been performed with tools of the FAST program code package. Electron Beam dynamics simulations were performed by using the ASTRA code, while the GENESIS 1.3 code was used to study the SASE process. The results of these studies are presented and discussed in this paper.  
 
MOP059 Beam Dynamic Simulations for Single Spike Radiation with Short-Pulse Injector Laser at FLASH laser, operation, electron, radiation 173
 
  • M. Rehders
    University of Hamburg, Hamburg, Germany
  • J. Rönsch-Schulenburg
    CFEL, Hamburg, Germany
  • J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • S. Schreiber
    DESY, Hamburg, Germany
  
  Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301
This paper discusses the generation of single spike SASE pulses at soft x-ray wavelength at the free-electron laser FLASH by using very short electron bunches of only a few micrometer bunch length. In order to achieve these extremely short bunch lengths, very low bunch charges (in the order of 20 pC) and short electron bunches exiting the photo-injector are required. For this, a new short-pulse injector laser with adjustable rms pulse duration in the range of 0.7 ps to 1.6 ps and bunch charges up to 200 pC was installed, extending the electron beam parameter range before bunch compression in magnetic chicanes. Beam dynamic studies have been performed to optimize the injection and compression of low-charge electron bunches by controlling the effect of coherent synchrotron radiation and space-charge induced bunch lengthening and emittance growth. Optimization includes the pulse parameters of the injector laser. The simulation codes ASTRA, CSRtrack and Genesis 1.3 were employed. 		 
 
MOP061 Electron Beam Delays for Improved Temporal Coherence and Short Pulse Generation at SwissFEL undulator, FEL, electron, radiation 181
 
  • N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  
  Proposals have been made for the introduction of magnetic electron beam delays in between the undulator modules of a long sectional FEL undulator - these can be used for the generation of trains of FEL pulses which can individually be shorter than the FEL cooperation time [*] or to greatly improve the temporal coherence of the FEL output compared to the nominal SASE configuration [**,***,***]. This paper comprises a feasibility study of the application of these techniques to the SwissFEL hard X-Ray beamline. Three-dimensional simulations are used to investigate the potential photon output.
[*] N.R. Thompson and B.W.J. McNeil, PRL 100:203901, 2008.
[**] N.R. Thompson et al. In Proc IPAC2010, pages 2257–2259, 2010
[***] J. Wu, A. Marinelli, and C. Pellegrini. Proc FEL2012, 2012. 		 
 
MOP068 Suppression of the Fundamental Frequency for a Successful Harmonic Lasing in SASE FELs undulator, FEL, electron, photon 215
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Harmonic lasing in X-ray FELs has recently attracted a significant attention and is now seriously considered as a potential method for generation of brilliant photon beams at short wavelengths. It is clear, however, that for a successful harmonic lasing one has to suppress the fundamental. In this paper we discuss different methods for such a suppression: phase shifters, intraundulator spectral filtering, switching between the 3rd and the 5th harmonics etc.  
 
MOP070 Design Study for the PEHG Experiment at SDUV-FEL electron, FEL, experiment, bunching 219
 
  • C. Feng, H.X. Deng, B. Liu, D. Wang, X.T. Wang, M. Zhang, T. Zhang, W. Zhang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  
  Funding: This work was partially supported by National Natural Science Foundation of China (11475250, 11175240 and 11205234)
In this paper, design studies for the proof-of-principle experiment of the recently proposed phase-merging enhanced harmonic generation (PEHG) mechanism are presented. A dogleg and a new designed transverse gradient undulator should be added in the undulator system of SDUV-FEL to perform the phase-merging effect. With the help of 3D simulation codes, we show the possible performance of PEHG with the realistic parameters of SDUV-FEL.
* H. Deng, C. Feng, Phys. Rev. Lett. 111, 084801.
** C. Feng, H. Deng, D. Wang, Z. Zhao, New J. Phys.,16, 043021.
*** C. Feng, T. Zhang, H. Deng, Z. Zhao, Phys. Rev. ST Accel. Beams 17, 070701.
 		 
 
MOP079 Generation of Multiple Coherent Pulses in a Superradiant Free-Electron Laser electron, FEL, radiation, undulator 233
 
  • X. Yang, S. Seletskiy
    BNL, Upton, Long Island, New York, USA
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  
  We analyze the structure of the tail of a superradiant pulse, which is constituted by a train of sub-pulses with decaying amplitudes. We show how a trailing pulse, with pi phase advance from the leading pulse, is generated at the falling edge of the leading superradiant pulse, where the corresponding phase space is deeply saturated and the electrons become de-trapped by the reduced ponderomotive potential. Once the trailing pulse gains enough energy, it generates a second trailing pulse, and the process takes place again. By performing detailed simulations of the resulting electron phase space distribution and the FEL pulse spectral and temporal structure with PERSEO, we confirm that the deformation and re-bunching of the longitudinal phase space create a sequence of pulses. These results are compared to 3D simulations using the FEL code GENESIS 1.3 showing a good agreement.  
 
MOP083 Start-to-End Simulation for FLASH2 HGHG Option undulator, radiation, electron, FEL 244
 
  • G. Feng, S. Ackermann, J. Bödewadt, W. Decking, M. Dohlus, Y.A. Kot, T. Limberg, M. Scholz, I. Zagorodnov
    DESY, Hamburg, Germany
  • K.E. Hacker
    DELTA, Dortmund, Germany
  • T. Plath
    Uni HH, Hamburg, Germany
  
  The Free-electron laser in Hamburg (FLASH) is the first FEL user facility to have produced extreme ultraviolet (XUV) and soft X-ray photons. In order to increase the beam time delivered to users, a major upgrade of FLASH named FLASH II is in progress. The electron beamline of FLASH2 consists of diagnostic and matching sections, a seeding undulator section and a SASE undulator section. In this paper, results from a start-to-end simulation for a FLASH2 High-Gain Harmonic Generation (HGHG) option are presented. For the beam dynamics simulation, space charge, coherent synchrotron radiation (CSR) and longitudinal cavity wake field effects are taken into account. In order to get electron beam bunches with small correlated and uncorrelated energy spread, RF parameters of the accelerating modules have been optimized as well as the parameters of the bunch compressors. Radiation simulations for the modulator and the radiator have been done with code Genesis 1.3 by using the particle distribution generated from the beam dynamics simulation. The results show that for a single stage HGHG, 33.6 nm wavelength FEL radiation can be seeded at FLASH2 with a 235 nm seeding laser.  
 
MOP090 Soft X-ray Self-seeding Simulation Methods and their Application for LCLS undulator, radiation, FEL, optics 264
 
  • S. Serkez
    DESY, Hamburg, Germany
  • Y. Ding, Z. Huang, J. Krzywinski
    SLAC, Menlo Park, California, USA
  
  Self-seeding is a promising approach to significantly narrow the SASE bandwidth of XFELs to produce nearly transform-limited pulses. We study radiation propagation through the grating monochromator installed at LCLS. The monochromator design is based on a toroidal variable line spacing grating working at a fixed incidence angle mounting without an entrance slit. It covers the spectral range from 500eV to 1000eV. The optical system was studied using wave optics method to evaluate the performance of the self-seeding scheme. Our wave optics analysis takes into account the finite size of the coherent source, third-order aberrations and height error of the optical elements. Wave optics is the only method available, in combination with FEL simulations, to simulate performance of the monochromator without exit slit. Two approaches for time-dependent simulations are presented, compared and discussed. Also pulse-front tilt phenomenon effect is illustrated.  
 
MOP095 HGHG AND EEHG MICROBUNCHES WITH CSR AND LSC electron, FEL, dipole, radiation 275
 
  • K.E. Hacker
    DELTA, Dortmund, Germany
  
  Funding: Work supported by BMBF (contract 05K13PE3) and DESY
Longitudinal space charge (LSC) forces in a drift and coherent synchrotron radiation (CSR) in a chicane are relevant for high gain harmonic generation (HGHG) and echo enabled harmonic generation (EEHG) seeding designs. These factors determine whether or not the modulator can be located significantly upstream of the radiator. The benefits and dangers of having a drift in between the radiator and the modulator are investigated and a measurement of the LSC enabled reduction of the energy spread of a seeded beam is presented. 		 
 
MOP096 Enhancing the Harmonic Content of an HGHG Microbunch electron, laser, undulator, bunching 281
 
  • K.E. Hacker
    DELTA, Dortmund, Germany
  
  Funding: BMBF grant 05K10PE1 and DESY
High Gain Harmonic Generation (HGHG) seeding has been demonstrated in the visible and ultraviolet, but it is limited in performance at high harmonics of the seed by the initial uncorrelated energy spread of the electron beam. A recent proposal from SINAP using a chirped electron beam and a canted pole undulator has suggested a new mechanism for cooling the uncorrelated energy spread of the electron beam in order to improve the performance of HGHG seeding at high harmonics. This note reviews the mechanism, the limitation of the concept and extrapolates to some new concepts using analogous mechanisms derived from transverse gradients of the laser properties. The impact of CSR wakes on the vanishingly short microbunches produced by the methods are also investigated.
[1] H. Deng and C. Feng, Phys. Rev. Lett. 111, 084801 (2013) 		 
 
MOC03 Radiation Properties of Tapered Hard X-ray Free Electron Lasers radiation, electron, FEL, undulator 300
 
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, USA
  • S.D. Chen
    NCTU, Hsinchu, Taiwan
  • K. Fang, C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  • S. Serkez
    DESY, Hamburg, Germany
  
  We perform an analysis of the transverse coherence of the radiation from a TW level tapered hard X-ray Free Electron Laser (FEL). The radiation properties of the FEL are studied for a Gaussian, parabolic and uniform transverse electron beam density profile in a 200-m undulator at a resonant wavelength of 1.5 Angstrom. Simulations performed using the 3-D FEL particle code GENESIS show that diffraction of the radiation occurs due to a reduction in optical guiding in the tapered section of the undulator. This results in an increasing transverse coherence for all three transverse electron beam profiles. We determine that for each case considered the radiation coherence area is much larger than the electron beam spot size, making X-ray diffraction experiments possible for TW X-ray FELs.  
slides icon Slides MOC03 [3.797 MB]  
 
MOC04 Chirped and Modulated Electron Pulse Free Electron Laser Techniques electron, undulator, radiation, FEL 303
 
  • J. Henderson, L.T. Campbell, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  
  Funding: We acknowledge STFC MoA 4132361; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Jlich Supercomputing Centre (JSC), under project HHH20
A potential method to improve the free electron laser's output when the electron pulse has a large energy spread is investigate and results presented. A simplified model is the first given, in which there are a number of linearly chirped beamlets equally separated in energy and time. By using chicanes, radiation from one chirped beamlet is passed to the next, helping to negate the effect of the beamlet chirps and maintaining resonant interactions. Hence the addition of chicane allow the electrons to interact with a smaller range of frequencies (Δ ω <2 ρ γr), sustaining the FEL interaction. One method to generate such a beamlet structure is presented and is shown to increase FEL performance by two orders of magnitude. 		 
slides icon Slides MOC04 [6.777 MB]  
 
TUB03 FEL Overcompression in the LCLS electron, experiment, FEL, diagnostics 337
 
  • J.L. Turner, F.-J. Decker, Y. Ding, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.J. Welch, F. Zhou
    SLAC, Menlo Park, California, USA
  
  Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
Overcompression of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center is studied. The studies and operational implications are summarized in this talk. 		 
slides icon Slides TUB03 [4.493 MB]  
 
TUP016 Quasi-optical Theory of Terahertz Superradiance from an Extended Electron Bunch electron, radiation, resonance, wakefield 391
 
  • N.S. Ginzburg, A. Malkin, A. Sergeev, V.Yu. Zaslavsky, I.V. Zotova
    IAP/RAS, Nizhny Novgorod, Russia
  
  Funding: This study was supported by the Russian Foundation for Basic Research (project no. 14-08-01180) and the Dynasty Foundation.
We consider superradiance of an extended relativistic electron bunch moving over a periodically corrugated surface for the generation of multi-megawatt terahertz pulses*. To study the above process we have developed a three-dimensional, self-consistent, quasi-optical theory of Cherenkov stimulated emission which includes a description of the formation of evanescent waves near the corrugated surface and its excitation by RF current induced in the electron bunch. Results obtained in the framework of a quasi-optical model were confirmed by direct CST STUDIO PIC simulations. There is a possibility of advancement towards still shorter wavelengths (infrared and optical), which can be achieved by decreasing the period of the diffraction gratings and increasing the density and energy of the particles in the electron bunches. Increase of coupling impedance can be obtained by using inclined incidence of electron bunch on corrugated surface (clinotron configuration).
Ginzburg N.S et al. Phys. Rev. Lett. 2013. V.110, Iss.18. 184801.
 		 
 
TUP017 Using Lorentz Transformations for Simulations of Wiggler Superradiance from the Picosecond Electron Bunches electron, undulator, radiation, scattering 395
 
  • A. Malkin, N.S. Ginzburg, A.A. Golovanov, I.V. Zotova
    IAP/RAS, Nizhny Novgorod, Russia
  • V.P. Tarakanov
    LPI, Moscow, Russia
  
  Funding: This work was supported by Russian Foundation for Basic Research under Grant No 12-02-01152.
In this paper we present a theoretical analysis of superradiance (SR) from picosecond electron bunches wiggling in periodical undulator field based both on the method of averaged ponderomotive force and on a direct numerical PIC (particle-in-cell) simulation. Within both approaches the analysis takes place in the reference frame co-moving with electrons which allows simplifying the procedure of simulation significantly due to the fact that all the spatial scales including the radiation wavelength, the length of the beam and the length of the pump field pacet into which the undulator field is transformed are of the same order. We show that in the reference frame the SR effect can be interpreted as a formation of the distributed Bragg mirror in the bulk of the electron beam which is effectively reflecting (scattering) the pump wave. A possibility of generation of multimegawatt pulses in terahertz and far infrared wave ranges is demonstrated. 		 
 
TUP020 MINERVA, a New Code to Model Free-Electron Lasers FEL, undulator, electron, experiment 408
 
  • H. Freund, P.J.M. van der Slot
    CSU, Fort Collins, Colorado, USA
  • P.J.M. van der Slot
    Mesa+, Enschede, The Netherlands
  
  Simulation codes modelling the interaction of electrons with an optical field inside an undulator are an essential tool for understanding and designing free-electron lasers (FELs). As there exists a large variety of FELs ranging from long-wavelength oscillators using partial wave guiding to soft and hard x-ray FELs that are either seeded or starting from noise, a simulation code should be capable of modelling this huge variety of FEL configurations. A new code under development, named MINERVA, will be capable of modelling such a large variety of FELs. The code uses a modal expansion for the optical field, e.g., a Gaussian expansion for free-space propagation, and an expansion in waveguide modes for propagation at long wavelengths, or a combination of the two for partial guiding at THz frequencies. MINERVA uses the full Newton-Lorentz force equation to track the particles through the optical and magnetic fields. To allow propagation of the optical field outside the undulator and interact with optical elements, MINERVA interfaces with the optical propagation code OPC to model oscillators. Here we describe the main features of MINERVA and give various examples of its capabilities.  
 
TUP022 The Implementation of 3D Undulator Fields in the Unaveraged FEL Simulation Code Puffin undulator, electron, FEL, focusing 416
 
  • J. Henderson, L.T. Campbell, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • A.R. Maier
    CFEL, Hamburg, Germany
  • A.R. Maier
    Uni HH, Hamburg, Germany
  
  Funding: We acknowledge STFC MoA 4132361; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Jlich Supercomputing Centre (JSC), under project HHH20
The FEL simulation code Puffin is modified to include 3D magnetic undulator fields. Puffin, having previously used a 1D undulator field, is modified to accommodate general 3D magnetic fields. Both plane and curved pole undulators have been implemented. The electron motion for both agrees with analytic predictions. 		 
 
TUP025 TW X-ray Free Electron Laser Optimisation by Transverse Pulse Shaping electron, FEL, radiation, undulator 425
 
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, USA
  • C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  
  We study the dependence of the peak power of a 1.5 Angstrom TW, tapered X-ray free-electron laser on the transverse electron density distribution. Multidimensional optimization schemes for TW hard X-Ray free electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to a Gaussian distribution. The optimizations are performed for a 200 m undulator and a resonant wavelength of 1.5 Angstrom using the fully 3-dimensional FEL particle code GENESIS. The study shows that the flatter transverse electron distributions enhance optical guiding in the tapered section of the undulator and increase the maximum radiation power from a maximum of 1.56 TW for a transversely Gaussian beam to 2.26 TW for the parabolic case and 2.63 TW for the uniform case. Spectral data also shows a 30-70 % reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian.  
 
TUP027 Initial Value Problem for an FEL Driven by an Asymmetric Electron Beam FEL, electron, radiation, undulator 433
 
  • P. Baxevanis, R.D. Ruth
    SLAC, Menlo Park, California, USA
  
  FEL configurations in which the driving electron beam is not axially symmetric (round) are important in the study of novel concepts (such as TGU-based FELs) but also become relevant when one wishes to explore the degree to which the deviation from symmetry-inevitable in practical cases-affects the performance of more conventional FEL schemes. In this paper, we present a technique for solving the initial value problem of such an asymmetric FEL. Extending an earlier treatment of ours, we start from a self-consistent, fully 3D, evolution equation for the complex amplitude of the electric field of the FEL radiation, which is then solved by expanding the radiation amplitude in terms of a set of orthogonal transverse modes. The numerical results from such an analysis are in good agreement with simulation and provide a full description of the radiation in the linear regime. Moreover, when the electron beam sizes are constant, this approach can be used to verify the predictions of the standard eigenmode formalism.  
 
TUP028 Mode Contents Analysis of a Tapered Free Electron Laser FEL, undulator, electron, laser 437
 
  • S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  • S.D. Chen, C.-S. Hwang
    NCTU, Hsinchu, Taiwan
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, USA
  • K. Fang, S.-Y. Lee
    Indiana University, Bloomington, Indiana, USA
  • C.-S. Hwang
    NSRRC, Hsinchu, Taiwan
  • S. Serkez
    DESY, Hamburg, Germany
  
  For the ultimate use for the scientific experiments, the free electron laser (FEL) will propagate for long distance, much longer than the Rayleigh range, after exiting the undu- lator. To characterize the FEL for this purpose, we study the electromagnetic field mode components of the FEL photon beam. With the mode decomposition, the transverse coher- ence can be analyzed all along. The FEL here in this paper is a highly tapered one evolving through the exponential growth and then the post-saturation taper. Modes contents are analyzed for electron bunch with three different types of transverse distribution: flattop, Gaussian, and parabolic. The tapered FEL simulation is performed with Genesis code. The FEL photon beam transverse electric field is decom- posed with Gaussian-Laguerre polynomials. The evolutions of spot size, source location, and the portion of the power in the fundamental mode are discussed here. The approach can be applicable to various kind scheme of FEL.  
 
TUP029 iSASE Study electron, FEL, radiation, undulator 442
 
  • K. Fang
    Indiana University, Bloomington, Indiana, USA
  • S.D. Chen
    NCTU, Hsinchu, Taiwan
  • S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, USA
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  
  Improved Self Amplified Spontaneous Emission (iSASE) is a scheme that reduces FEL bandwidth by increasing phase slippage between the electron bunch and radiation field. This is achieved by repeatedly delaying electrons using phase shifters between undulator sections. Genesis code is modified to facilitate this simulation. With this simulation code, the iSASE bandwidth reduction mechanism is studied in detail. A Temporal correlation function is introduced to describe the similarity between the new grown field from bunching factor and the amplified shifted field. This correlation function indicates the efficiency of iSASE process.  
 
TUP031 FEL Code Comparison for the Production of Harmonics via Harmonic Lasing FEL, electron, radiation, undulator 451
 
  • G. Marcus, W.M. Fawley
    SLAC, Menlo Park, California, USA
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Harmonic lasing offers an attractive option to significantly extend the photon energy range of FEL beamlines. Here, the fundamental FEL radiation is suppressed by various combinations of phase shifters, attenuators, and detuned undulators while the radiation at a desired harmonic is allowed to grow linearly. The support of numerical simulations is extensively used in evaluating the performance of this scheme. This paper compares the results of harmonic growth in the harmonic lasing scheme using three FEL codes: FAST, GENESIS, and GINGER.  
 
TUP032 FEL Simulation and Performance Studies for LCLS-II electron, undulator, FEL, radiation 456
 
  • G. Marcus, Y. Ding, P. Emma, Z. Huang, T.O. Raubenheimer, L. Wang, J. Wu
    SLAC, Menlo Park, California, USA
  
  The design and performance of the LCLS-II free-electron laser beamlines are presented using start-to-end numerical particle simulations. The particular beamline geometries were chosen to cover a large photon energy tuning range with x-ray pulse length and bandwidth flexibility. Results for self-amplified spontaneous emission and self-seeded operational modes are described in detail for both hard and soft x-ray beamlines in the baseline design.  
 
TUP033 Broadly Tunable Free-Electron Laser for Four-wave Mixing Experiments with Soft X-ray Pulses electron, undulator, FEL, laser 461
 
  • G. Marcus
    SLAC, Menlo Park, California, USA
  • G. Penn
    LBNL, Berkeley, California, USA
  • A. Zholents
    ANL, Argonne, Illinois, USA
  
  This paper examines a FEL design for the production of three soft x-ray pulses from a single electron beam suitable for four-wave mixing experiments. Independent control of the wavelength, timing and angle of incidence of the three ultra-short, ultra-intense pulses with exquisite synchronization is critical. A process of selective amplification where a chirped electron beam and a tapered undulator are used to isolate the gain region to only a short fraction of the electron beam is explored in detail. Numerical particle simulations are used to demonstrate the essential features of this scheme in the context of the LCLS-II design study.  
 
TUP035 Investigation of Reverse Taper to Optimize the Degree of Polarization for the Delta Undulator at the LCLS undulator, radiation, polarization, bunching 465
 
  • J.P. MacArthur
    Stanford University, Stanford, California, USA
  • Z. Huang, A. Lutmann, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner
    SLAC, Menlo Park, California, USA
  
  Funding: U.S. Department of Energy under contract No. DE-AC02-76SF00515
A 3.2 m adjustable phase Delta undulator* will soon be installed on the last girder of the LCLS undulator line. The Delta undulator will act as an afterburner terminating the 33 undulator line, providing arbitrary polarization control to users. Two important figures of merit for users will be the degree of polarization and the x-ray yield. In anticipation of this installation, machine development time at the LCLS was devoted to maximizing the final undulator x-ray contrast and yield with a standard canted pole undulator acting as a stand in for the Delta undulator. Following the recent suggestion** that a reverse taper (dK/dz > 0) in the main undulator line could suppress linearly polarized light generated before an afterburner while still producing the requisite microbunching, we report on a reverse taper study at the LCLS wherein a yield contrast of 15 was measured along the afterburner. We also present 1D simulations comparing the reverse taper technique to other schemes.
* Nuhn, H.-D., Anderson, S., Bowden, G., Ding, Y., Gassner, G., et al., (2013).
** Schneidmiller, E. A. and Yurkov, M. V., Phys. Rev. ST Accel. Beams 16, 110702 (2013). 		 
 
TUP036 Observation of Smith-Purcell Radiation at 32 GHz from a Multi-channel Grating with Sidewalls radiation, experiment, electron, free-electron-laser 470
 
  • J.T. Donohue
    CENBG, Gradignan, France
  • J. Gardelle, P. Modin
    CEA, LE BARP cedex, France
  
  In a demonstration experiment at 5 GHz, we found copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave, when the grating had sidewalls. Reaching higher frequencies requires a reduction in the size of the grating, which leads to a considerable reduction in power. To partially compensate this, we suggested superposing several copies of the reduced grating in parallel. A test of this concept has been performed with a seven-channel grating, at a frequency near 32 GHz. The SP radiation signals were observed directly with a fast oscilloscope. Power levels were of order 5 kW, in fair agreement with three-dimensional simulations made using the code "MAGIC".  
 
TUP057 Development of Compact THz-FEL System at Kyoto University undulator, gun, electron, FEL 501
 
  • S. Suphakul, T. Kii, H. Ohgaki, Y. Tsugamura, H. Zen
    Kyoto University, Kyoto, Japan
  • Q.K. Jia
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  We are developing a compact accelerator based terahertz (THz) radiation source by free-electron laser (FEL) at the Institute of Advanced Energy, Kyoto University. The system consists of a 1.6 cell BNL type photocathode RF-gun, a focusing solenoid magnet, a magnetic bunch compressor, focusing quadrupoles and an undulator. The system generates an ultra-short electron pulse in a few hundred femtoseconds shorter than radiation wavelength, resulting in super-radiant emission from the undulator. The target radiation wavelength is 100 to 300 μm. A tracking simulation and optimization are performed by using PARMELA and General Particle Tracer (GPT) code. The FEL radiations are analyzed by a 1 dimensional FEL theory. The design parameters, simulation results and status are reported and discussed in this paper.  
 
TUP070 Numerical Calculation of Diffraction Loss for Characterisation of a Partial Waveguide FEL Resonator FEL, laser, electron, radiation 521
 
  • Q. Fu, B. Qin, P. Tan, K. Xiong, Y.Q. Xiong
    HUST, Wuhan, People's Republic of China
  
  Waveguide is widely used in long wavelength Free-Electron Lasers to reduce diffraction losses. In this paper the amplitude and phase transverse distribution of light emission produced in a partial-waveguide FEL resonator is calculated by Fresnel principle. To acquire high power out-coupled and optimize resonator structure of HUST THz-FEL, the characterisation of reflecting mirror is discussed to reduce diffraction loss.  
 
TUP093 A Beam Test of Corrugated Structure for Passive Linearizer quadrupole, electron, linac, controls 593
 
  • H.-S. Kang, J.H. Hong
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  A dechirper which is a vacuum chamber of two corrugated, metallic plates with adjustable gap was successfully tested at Pohang, in August 2013. Another beam test was carried out to test the same structure to see if the corrugated plates may work as a linearizer. The test result will be presented together with the simulation result.  
 
WEA04 First Lasing from a High Power Cylindrical Grating Smith-Purcell Device electron, radiation, experiment, cathode 611
 
  • H. Bluem, R.H. Jackson, J.D. Jarvis, A.M.M. Todd
    AES, Medford, New York, USA
  • J.T. Donohue
    CENBG, Gradignan, France
  • J. Gardelle, P. Modin
    CEA, LE BARP cedex, France
  
  Funding: Work supported by ONR under Contract No. N00014-10-C-0191 and N62909-13-1-N62.
Many applications of THz radiation remain impractical or impossible due to an absence of compact sources with sufficient power. A source where the interaction occurs between an annular electron beam and a cylindrical grating is capable of generating high THz power in a very compact package. The strong beam bunching generates significant power at the fundamental frequency and harmonics. A collaboration between Advanced Energy Systems and CEA/CESTA has been ongoing in performing proof-of-principle tests on cylindrical grating configurations producing millimeter wave radiation. First lasing was achieved in such a device. Further experiments performed with a 6 mm period grating produced fundamental power at 15 GHz, second harmonic power at 30 GHz and although not measured, simulations show meaningful third harmonic power at 45 GHz. Comparison with simulations shows very good agreement and high conversion efficiency. Planned experiments will increase the frequency of operation to 100 GHz and beyond. Ongoing simulations indicate excellent performance for a device operating at a fundamental frequency of 220 GHz with realistic beam parameters at 10 kV and simple extraction of the mode. 		 
slides icon Slides WEA04 [2.344 MB]  
 
THP003 Two Charges in the Same Bunch Train at the European XFEL laser, operation, emittance, solenoid 678
 
  • Y.A. Kot, T. Limberg, I. Zagorodnov
    DESY, Hamburg, Germany
  
  The European XFEL has been initially designed for the operation with bunch charge of 1 nC (*) which was later extended down to 20 pC (**). An important upgrade of this extension might be the ability to operate different bunch charges in the same RF pulse. In this paper we assume the nominal design of the XFEL injector which means in particular that both charges in the same RF pulse experience the same solenoid field and are generated by the laser of the same rms size. We discuss the requirements which the combined working points of the injector have to fulfil and show the results of the complete start to end (S2E) and SASE simulations for the simultaneous operation of 250 pC and 500 pC bunch charges.
* DESY XFEL Project Group "The European X-Ray Free-Electron Laser. Technical Design Report" July 2007
** W. Decking and T. Limberg "European XFEL. Post-TDR Description" February 2013 		 
 
THP004 Start-to-End Error Studies for FLUTE laser, linac, timing, gun 682
 
  • M. Weber, A.-S. Müller, S. Naknaimueang, M. Schuh, M. Schwarz, P. Wesolowski
    KIT, Karlsruhe, Germany
  
  FLUTE, a new linac based test facility and THz source, is currently under construction at the Karlsruhe Institute of Technology (KIT) in collaboration with DESY and PSI. With a repetition rate of 10 Hz, electron bunches with charges from 1 pC to 3 nC will be accelerated up to 40-50 MeV and then compressed longitudinally in a magnetic chicane to generate intense coherent THz radiation. Since the stability and repeatability of longitudinal bunch profiles are essential for optimum compression and THz radiation properties, simulation-based start-to-end error studies using the tracking code ASTRA have been performed to determine the influence of the machine elements on the bunches. Thus, critical parameters are identified and their respective tolerance ranges defined. In this contribution a summary of the error studies will be given.  
 
THP012 Error Analysis for Linac Lattice of Hard X-ray FEL Line in PAL-XFEL* emittance, linac, lattice, alignment 703
 
  • H. Yang, J.H. Han, H.-S. Kang, I.S. Ko
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  Funding: *This work was supported by MSIP, Korea.
PAL-XFEL consists of the hard x-ray line for 0.06 – 1-nm FEL and the soft x-ray line for 1 – 10-nm FEL. The linac of hard x-ray line is designed to generate 10-GeV, 200-pC, and 3-kA electron beam. It consists of S-band accelerating columns, an X-band linearizer, three bunch compressors (BC). We conduct error simulation in order to evaluate the tolerances of machine parameters and alignments. First, the machine tolerances and beam jitter levels are calculated in the simulations with dynamic errors and we find out the optimized lattice to satisfy the target tolerance of machine. Second, we conduct simulations with misalignment. We quantify the emittance dilution by misalignments, especially those of BCs. In order to compensate the misalignments, the methods of beam correction like Beam Based Alignment (BBA) are presented and the effects of emittance improvements are calculated. 		 
poster icon Poster THP012 [0.736 MB]  
 
THP016 Optimization of FEL Performanceby Dispersion-based Beam-tilt Correction FEL, electron, lattice, radiation 714
 
  • M.W. Guetg, S. Reiche
    PSI, Villigen PSI, Switzerland
  
  In Free Electron Lasers (FEL) the beam quality is of crucial importance for the radiation power. A transverse centroid misalignment of longitudinal slices in an electron bunch reduces the effective overlap between radiation field and electron bunch. This leads to a reduced bunching and decreased FEL performance. The dominant sources of slice misalignments in FELs are the coherent synchrotron radiation within bunch compressors as well as transverse wake fields in the accelerating cavities. This is of particular importance for over-compression, which is required for one of the key operation modes for the SwissFEL under construction at the Paul Scherrer Institute in Switzerland. The slice centroid shift can be corrected using multi-pole magnets in dispersive sections, e.g. the bunch compressors. First and second order corrections are achieved by pairs of sextupole and quadrupole magnets in the horizontal plane while skew quadrupoles correct to first order in the vertical plane.  
 
THP023 Simulation of Alpha Magnet Elements in Dipole-only Tracking Codes dipole, electron, beam-transport, coupling 735
 
  • J.W. Lewellen, F.L. Krawczyk
    LANL, Los Alamos, New Mexico, USA
  
  Alpha magnets are used in a variety of ion-beam and low-energy (< 5 MeV) electron-beam transport systems as both “switchyard” elements and as bunch compressors. A unique feature of the alpha-magnet is its natively achromatic transport. Particles of different energies, injected at a specific location and angle, will exit at the same location and (symmetry-reflected) angle but with a different time-of-flight. Despite the general usefulness of alpha magnets in low-energy beam transport and compression schemes, few simulation codes support them as native elements. The (arguably) most-common codes used for injector design, PARMELA, ASTRA and GPT (listed in order of their release) do not support alpha magnets natively, but do support modeling of space-charge-dominated beams through dipole magnets. As a result, the most commonly used injector design codes are unable to incorporate one of the most useful and interesting beam transport devices. We present a method for simulating an alpha magnet in a tracking code using dipole elements. As elegant supports both dipoles and alpha magnets, it is used to provide a basic check of the approximation and a means of estimating the induced errors.  
 
THP026 Design Study of LCLS Chirp-Control with a Corrugated Structure wakefield, emittance, dipole, quadrupole 748
 
  • Z. Zhang, K.L.F. Bane, Y. Ding, Z. Huang, R.H. Iverson, T.J. Maxwell, G.V. Stupakov, L. Wang
    SLAC, Menlo Park, California, USA
  • P. Frigola, M.A. Harrison, M. Ruelas
    RadiaBeam, Santa Monica, California, USA
  
  The purpose of this paper is to investigate the use of flat metallic plates with small corrugations as a passive dechirper, studying its effects on beam dynamics. Similar systems have been tested in Pohang and Brookhaven at relatively low energies (~100 MeV) and with relatively long bunches (>1ps) [*,**]. Four meters of such a structure are being machined by Radiabeam Systems for use in the LCLS with a high energy and femtosecond electron beam. In this paper we use a field matching program to obtain the longitudinal and transverse wakes for the purpose of the LCLS dechirper design. In addition, we fit the longitudinal wake to simple functions, so that one can obtain the wake without resorting to the field matching program. Since the transverse wakes–both dipole and quadrupole wakes–are strong, we include beam dynamics simulations to find the tolerances for injection jitter and misalignment in the LCLS.
* P. Emma, et al. PRL 112, 034801
** M. Harrison, et al., NaPAc 2013, Pasadena, USA 		 
 
THP029 MOGA OPTIMIZATION DESIGN OF LCLS-II LINAC CONFIGURATIONS linac, emittance, undulator, FEL 763
 
  • L. Wang, P. Emma, Y. Nosochkov, T.O. Raubenheimer, M. Woodley, F. Zhou
    SLAC, Menlo Park, California, USA
  • C. F. Papadopoulos, J. Qiang, M. Venturini
    LBNL, Berkeley, California, USA
  
  The Linac Coherent Light Source II (LCLS-II) will generate extremely intense X-ray flashes to be used by researchers from all over the world. The FEL is powered by 4 GeV superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. LCLS-II will provide large flexibility in bunch charge and peak current. Multi-Objective Genetic Algorithm (MOGA) is applied to optimize the machine parameters including bunch compressors system, linearizer, de-chirper, RF phase and laser heater, in order to minimize the energy spread, collective effects and emittance. The strong resistive wall wake field along the 2km bypass beam line acts as a natural de-chirper. This paper summarizes the optimization of various configurations.  
poster icon Poster THP029 [0.702 MB]  
 
THP032 Effects of Potential Energy Spread on Particle Dynamics in Magnetic Bending Systems transverse-dynamics, optics, space-charge, electron 779
 
  • R. Li
    JLab, Newport News, Virginia, USA
  
  Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Understanding CSR effects for the generation and transport of high brightness electron beams is crucial for designs of modern FELs. Most studies of CSR effects focus on the impacts of the longitudinal CSR wakefield. In this study, we investigate the impact of the initial retarded potential energy of particles, due to bunch collective interaction, on the transverse dynamics of particles on a curved orbit. It is shown that as part of the remnants of the CSR cancellation effect when both the longitudinal and transverse CSR fores are taken into account, this initial potential energy at the entrance of a bending system acts as a pseudo kinetic energy, or pseudo energy in short, because its effect on particle optics through dispersion and momentum compaction is indistinguishable from effect of the usual kinetic energy offset from the design energy. Our estimation indicates that the resulting effect of pseudo energy spread can be measurable only when the peak current of the bunch is high enough such that the slice pseudo energy spread is appreciable compared to the slice kinetic energy spread. The implication of this study on simulations and experiments of CSR effects will be discussed. 		 
 
THP034 Further Analysis of Corrugated Plate Dechirper Experiment at BNL-ATF wakefield, experiment, electron, free-electron-laser 788
 
  • M.A. Harrison, G. Andonian, P. Frigola, A.Y. Murokh, M. Ruelas, A.V. Smirnov
    RadiaBeam Systems, Santa Monica, California, USA
  • M.G. Fedurin
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work is supported by Department of Energy grant number DE-SC0009550.
RadiaBeam Systems successfully completed testing of a proof-of-concept corrugated plate dechirper at the Brookhaven National Laboratory Accelerator Test Facility.* Such passive devices should prove indispensable for the efficient operation of future XFEL facilities. These experiments demonstrated a narrowing of the energy spectrum in chirped beam bunches at 57.6 MeV. In this paper, we compare these results with results from Elegant simulations of the BNL-ATF beam. We also compare GdfidL simulations of the wakefield with the analytic results of Bane and Stupakov.**
* Harrison, M., et al "Removal of Residual Chirp in Compressed Beams Using a Passive Wakefield Technique." NaPAC13, 2013
** K. Bane, et al "Corrugated Pipe as a Beam Dechirper," SLAC-PUB-14925, 2012 		 
 
THP036 Benchmark and Simulation Design of a Low Energy Bunch Compressor gun, electron, space-charge, focusing 795
 
  • A. He, F.J. Willeke, L. Yang, L.-H. Yu
    BNL, Upton, Long Island, New York, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
  
  In the electron beam slicing method, a low energy bunch with very short and focused beam size is required to interact with the storage ring bunch. We have designed a low energy bunch compressor with BNL photocathode electron RF-gun by applying simulation code PARMELA. In this paper, in order to increase the repetition rate of the electron beam slicing system, we change the compressor’s RF gun from BNL RF-gun to LBNL’s VHF gun and redesign the compressor by applying IMPACT-T with both space charge effects and CSR effects considered. The benchmark between PARMELA and IMPACT-T has produced excellent agreement. The comparison of the CSR effects also shows the bunch can be compressed and focused to our desired size after optimization using code IMPACT-T with CSR effects turned on. The new compressor with high repetition rate still works in space charge dominated domain and the bunch with a negative energy chirp at the entrance of the chicane is compressed by a chicane with positive R56. After the optimization, we have achieved a low energy bunch with the 128 fs RMS bunch length, 42 μm and 25 μm RMS beam size in the vertical and horizontal directions respectively, at 22 MeV with 200 pC charge.  
 
THP054 Dark Current Studies at the APEX Photoinjector gun, cathode, electron, solenoid 855
 
  • R. Huang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • D. Filippetto, C. F. Papadopoulos, F. Sannibale
    LBNL, Berkeley, California, USA
  
  Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The increasing scientific demand for a high repetition rate FEL light source is driving the development of electron sources with high beam quality, delivering electron bunches at rates in the MHz range. An ongoing project to develop such a source is the Advanced Photoinjector Experiment (APEX) at LBNL. High brightness electron beams require high fields at the cathode during the electron emission. Such high fields associated with imperfections on the cathode surface area can induce undesired electron field emission (dark current). Excessive dark current can generate quenching of SRF structures and undesired radiation doses activating accelerator components and damaging undulator structures. In the present paper, we discuss the dark current studies performed at APEX. Field emitters in the cathode area have been localized and characterized, and techniques for minimizing dark current emission and to passively remove it have been investigated. 		 
 
THP060 Design of a Spatio-temporal 3-D Ellipsoidal Photo Cathode Laser System for the High Brightness Photo Injector PITZ laser, electron, cathode, photon 878
 
  • T. Rublack, J.D. Good, M. Khojoyan, M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • A.V. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky
    IAP/RAS, Nizhny Novgorod, Russia
  • I. Hartl, S. Schreiber
    DESY, Hamburg, Germany
  • E. Syresin
    JINR, Dubna, Moscow Region, Russia
  
  Funding: German Federal Ministry of education and Research, project 05K10CHE “Development and experimental test of a laser system for producing quasi 3D ellipsoidal laser pulses” and RFBR grant 13-02-91323.
Minimized emittance is crucial for improved operation of linac-based free electron lasers. Simulations have thus shown 3-D ellipsoidal photocathode laser pulses are superior to the standard Gaussian or cylindrical laser pulses in this manner. Therefore, in collaboration with the Joint Institute of Nuclear Research (JINR, Dubna, Russia) and the Photo Injector Test facility at DESY, Zeuthen (PITZ), a prototype system capable of producing spatio-temporal 3-D ellipsoidal pulses has been constructed at the Institute of Applied Physics (IAP, Nizhny Novgorod, Russia). The system consists of a dual-output, 1030 nm fiber laser coupled with disc amplifiers, a scheme based on Spatial Light Modulators for spatial and temporal pulse shaping of the primary output, a cross-correlator set up utilizing the secondary output to characterize the primary output, and finally frequency conversion to the UV. A preliminary, temporal ellipsoidal shaped IR pulse has been observed and measured so far at IAP RAS. As of writing, improvements and refinements of the system are ongoing and it is expected to replicate the finalized prototype at PITZ soon. 		 
 
THP092 Transition Radiation of an Electron Bunch and Imprint of Lorentz-Covariance and Temporal-Causality electron, radiation, diagnostics, optics 952
 
  • G.L. Orlandi
    PSI, Villigen PSI, Switzerland
  
  The study of Transition Radiation (TR) of a bunch of N electrons offers a precious insight into the role that Lorentz-covariance and temporal-causality play in an electromagnetic radiative mechanism of a relativistic beam. The contributions of the N single electrons to the radiation field are indeed characterized by emission phases from the metallic surface which are in a causality relation with the temporal sequence of the N particle collisions onto the radiating screen. The Lorentz-covariance characterizing the virtual quanta field of the relativistic charge is also expected to imprint the radiation field and the related energy spectrum. The main aspects of a Lorentz-covariance and temporal-causality consistent formulation of the TR energy spectrum of an electron bunch will be described.  
 
THP097 Longitudinal Response Matrix Simulations for the SwissFEL Injector Test Facility diagnostics, electron, laser, free-electron-laser 964
 
  • Á. Saá Hernández, F. Frei, R. Ischebeck
    PSI, Villigen PSI, Switzerland
  • B. Beutner
    DESY, Hamburg, Germany
  
  The Singular Value Decomposition (SVD) method has been applied to the SwissFEL Injector Test Facility to identify and better expose the various relationships among the possible jitter sources affecting the longitudinal phase space distribution and the longitudinal diagnostic elements that measure them. To this end, several longitudinal tracking simulations have been run using the Litrack code. In these simulations the RF and laser jitter sources are varied one-by-one within a range spanning twice their expected stability. The particle distributions have been dumped at the diagnostic locations and the measured quantities analyzed. A matrix has been built by linearly fitting the response of each measured quantity to each jitter source. This response matrix is normalized to the jitter source stability and the instrumentation accuracy, and it is inverted and analyzed using SVD. From the eigenvalues and eigenvectors the sensitivity of the diagnostics to the jitters can be evaluated and their specifications and locations optimized.  
 
THC03 Suppression of the CSR-induced Emittance Growth in Achromats using Two-dimensional point-kick Analysis dipole, emittance, optics, linear-collider 976
 
  • Y. Jiao, X. Cui, X.Y. Huang, G. Xu
    IHEP, Beijing, People's Republic of China
  
  Coherent synchrotron radiation (CSR) effect causes transverse emittance dilution in high-brightness light sources and linear colliders. Suppression of the emittance growth induced by CSR is essential and critical to preserve the beam quality and to help improve the machine performance. To evaluate the CSR effect analytically, we propose a novel method, named “two-dimensional point-kick analysis”. In this method, the CSR-induced emittance growth in an n-dipole achromat can be evaluated with the analysis of only the motion of particle in (x, x') two-dimensional plane with n-point kicks, which can be, to a large extent, counted separately. To demonstrate the effectiveness of this method, the CSR effect in a two-diople achromat and a symmetric TBA is studied, and generic conditions of suppressing the CSR-induced emittance growth, which are independent of concrete element parameters and are robust against the variation of initial beam distribution, are found. These conditions are verified with the ELEGANT simulations and can be rather easily applied to real machines.  
slides icon Slides THC03 [1.941 MB]