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simulation

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MOPPH003 VOLC: Volume Free Electron Laser Simulation Code electron, radiation, free-electron-laser, laser 14
 
  • S. Sytova
    Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk
  First lasing of Volume Free Electron Laser (VFEL) in mm wavelength range was obtained recently*. Мulti-wave volume distributed feedback where electromagnetic waves and electron beam spread angularly one to other in a spatially-periodic target is the VFEL distinctive feature**. Mathematical model and numerical methods for VFEL nonlinear stage simulation were proposed*** and implemented in computer code VOLC that means "VOLume Code". It was developed on the basis of multiple Fortran codes created in 1991-2006 years. VOLC allows to simulate different geometries of two- and three-wave VFEL in amplifier and oscillator regimes. Electron beam is modelled by averaging over initial phases of electrons. Dimensionality is 2D (one spatial coordinate and one phase space coordinate) plus time. All numerical results obtained using VOLC are in good agreement with analytical predictions of VFEL theory. Different roots to chaos in VFEL were investigated using VOLC. Some successful simulations of VFEL experimental setup at INP were carried out. A description of VOLC possibilities and representative numerical results are presented.

* V. G. Baryshevsky et al., NIMA483 (2002) 21. ** V. G. Baryshevsky, NIMA445 (2000) 281. *** K. Batrakov, S. Sytova, Computational Mathematics and Mathematical Physics 45 (2005) 666.

 
 
MOPPH004 Measurement and Analysis of CSR effects at FLASH space-charge, optics, diagnostics, acceleration 18
 
  • W. Decking, T. Limberg, M. Roehrs, B. Beutner
    DESY, Hamburg
  The vacuum-ultra-violet Free Electron Laser in Hamburg (FLASH) is a linac driven SASE-FEL. High peak currents are produced using magnetic bunch compression chicanes. In these magnetic chicanes, the energy distribution along an electron bunch is changed by effects of Coherent Synchrotron Radiation (CSR). Energy changes in dispersive bunch compressor chicanes lead to transverse displacements along the bunch. These CSR induced displacements are studied using a transverse deflecting rf-structure. Recent experiments and simulations concerning the charge dependence of such transverse displacements are presented and analyzed. In these experiments an over-compression scheme is used which reduces the peak current downstream the bunch compressor chicanes. Therefore other self interactions like space charge forces which might complicate the measurements are suppressed.  
 
MOPPH005 Improvements of the Tracking Code Astra for the Simulation of Dark Current Losses in the FLASH Linac gun, linac, space-charge, vacuum 22
 
  • S. M. Meykopff, L. Fröhlich
    DESY, Hamburg
  At the Free Electron Laser in Hamburg FLASH, the activation of components due to dark current emitted by the gun has become a serious problem. To improve the understanding of dark current transport in the linac, simulations with the Astra tracking code have been conducted. These studies require a big amount of computing time due to the high number of simulated macroparticles. Therefore, the parallelized version of Astra had to be enhanced by features like dynamic load balancing and an improved aperture model. The paper will provide an overview of the new features and discuss possible remedies of the dark current problem based on the simulation results.  
 
MOPPH015 Limit for Harmonic Conversion in a Single Cascade of Coherent Harmonic Generation bunching, electron, radiation, laser 50
 
  • G. De Ninno, E. Allaria
    ELETTRA, Basovizza, Trieste
  Harmonic generation is a reliable method for producing coherent high-brightness photon pulses from relativistic electron bunches. The standard process leading to Coherent Harmonic Generation (CHG) is initiated by a powerful seed laser. As a consequence, reaching short wavelengths generally requires a high order frequency conversion. For that reason some of the projects which are presently under development for coherent VUV and soft-Xray emission are based on a series of two or more consecutive "cascades". In these setups, the radiation produced into one CHG stage is used as a seed in a following CHG cascade. The required number of cascades is related to the maximum harmonic conversion which can be obtained in single stages. In this paper the mechanism underlying the CHG, i.e. the bunching creation into the modulator, is studied in detail and the physical limits for the single-stage CHG are investigated. The identification of the limiting parameters may allow the implementation of new methods for enhancing the conversion efficiency. One of these methods, which relies on a simple modification of the standard CHG scheme, has been recently proposed* and shown to be able to significantly improve the system performance. Results are confirmed by numerical simulations using the codes Ginger and Genesis. Expected impact on some of the existing projects for CHG is also presented.

* E. Allaria, G. De Ninno, Phys. Rev. Lett., to be published.

 
 
MOPPH019 Optimized Designs for CAEP IR Free-electron Laser coupling, free-electron-laser, laser, electron 58
 
  • Y. H. Dou, X. J. Shu
    IAP, Beijing
  The characteristics of CAEP IR free-electron laser are estimated and the optimized designs of the resonator parameters such as radius of output hole, the size of mirror, the resonator length is carried out using our 3D FEL oscillator code. Based on the appropriate parameters, the saturated power, output power, gain and construction of optical modes are calculated.  
 
MOPPH023 Enhancing FEL Power with Phase Shifters undulator, radiation, electron, linac 69
 
  • A. Chao, Z. Huang
    SLAC, Menlo Park, California
  • D. F. Ratner
    Stanford University, Stanford, Califormia
  Undulator taper is a well-known technique to increase the FEL efficiency past saturation by maintaining the resonant condition. In this paper, we demonstrate that shifting the electron bunch phase relative to the radiation is equivalent to tapering the undulator parameter. Using discrete phase changes derived from optimized undulator tapers for the LCLS x-ray FEL, we show that placing appropriate phase shifters between undulator sections can reproduce the power enhancement of these undulator tapers. The phase shifters are relatively easy to implement and operate, and hence can be used to aid or replace the undulator taper for optimizing the FEL performance.  
 
MOPPH041 Comparative Study of Electro-Optic Effect between Simulation and Measurement laser, electron, radiation, controls 104
 
  • J. Y. Huang, C. Kim, I. S. Ko, Y. W. Parc
    PAL, Pohang, Kyungbuk
  The short, intense, and low emittance electron beams are crucial to make high quality X-ray beam for X-ray free electron laser (XFEL). Electro-Optic Sampling (EOS) is a promising method to measure the electron bunch length non-destructively. A simulation study is done with the pulse propagation method, which utilizes Fourier transform to investigate the evolution of electromagnetic pulse inside the electro-optic (EO) crystal. The experimental result measured with spatial decoding method at Free electron LASer in Hamburg (FLASH) facility in Deutsches Elektronen-Synchrotron (DESY) is analyzed in terms of the relative phase shift between the horizontal and vertical component of the laser pulse. In this report, the experimental results expressed in terms of the "Relative Phase Shift Г" are compared with the simulation result. The simulation and the experimental result show similar values within reasonable error. The way to increase the signal level is also proposed.  
 
MOPPH050 Status of the Undulator System of the Seeded HGHG-FEL Test Bench at MAX-lab electron, radiation, undulator, laser 122
 
  • M. Brandin, F. Lindau, D. Pugachov, S. Thorin, S. Werin
    MAX-lab, Lund
  • W. Frentrup, A. Gaupp, K. Goldammer, K. Holldack, M. Scheer, J. Bahrdt
    BESSY GmbH, Berlin
  Within the EUROFEL Design Study a seeded HGHG-FEL will be set up at the 400 MeV linac at MAX-lab. The undulators and the dispersive section have been installed. A glass fibre based power meter system for integrated dose measurements as well as a Cherenkov system for a fast detection of electron losses have been integrated. We report on the performance of all components. Simulations on the acceptable radiation doses inside the undulator magnets will be presented. In the first step of commissioning the THz radiation as produced by the bunched electron beam inside the dispersive section will be used for the optimization of the longitudinal and transverse overlap of the electron beam and the laser beam.  
 
MOPPH051 Nonlinear Harmonic Generation in the BESSY Soft X-Ray FEL radiation, undulator, electron, laser 126
 
  • K. Goldammer
    BESSY GmbH, Berlin
  Free Electron Lasers do not only radiate at the fundamental frequency, they may also radiate coherently at higher harmonics. This process is referred to as nonlinear harmonic generation or NHG. NHG is of high interest, because it extends the FEL output wavelength of FELs to several harmonics of the FEL resonant frequency. In cascaded High Gain Harmonic Generation (HGHG) FELs, harmonic radiation may be used to improve frequency-conversion and reduce the number of HGHG-stages. BESSY proposes to build a cascaded HGHG FEL with three FEL lines. They cover a wavelength range of 51 nm (Low-Energy FEL) to 1.2 nm (High-Energy FEL) and consist of up to four HGHG-stages. In this paper, we present studies of the BESSY High-Energy FEL harmonic content performed with the upgraded version of the simulation code Genesis 1.3.  
 
MOPPH058 Status of the SPARX Project emittance, linac, undulator, radiation 142
 
  • D. Filippetto
    INFN/LNF, Frascati (Roma)
  The SPARX project consists in an Soft-X-ray-FEL facility jointly supported by MUR(Research Department of Italian Government), Regione Lazio, CNR, ENEA, INFN and the University of Roma Tor Vergata. It is the natural extension of the ongoing activities of the SPARC collaboration. The aim is the generation of electron beams characterized by ultra-high peak brightness at the energy of 1 and 2 GeV, for the first and the second phase respectively. The beam is expected to drive a single pass FEL experiment in the range of 13.5-6 nm and 6-1.5 nm, at 1 GeV and 2 GeV respectively, both in SASE and SEEDED FEL configurations. A hybrid scheme of RF and magnetic compression will be adopted, based on the expertise achieved at the SPARC. high brightness photoinjector presently under commissioning at Frascati INFN-LNF Laboratory.  
 
MOPPH061 Design of the PAL Test FEL Machine linac, undulator, emittance, electron 149
 
  • J. Choi, J. Y. Huang, H.-S. Kang, I. S. Ko, T.-Y. Lee, J.-S. Oh, S. J. Park, M. Kim
    PAL, Pohang, Kyungbuk
  • C. M. Yim
    POSTECH, Pohang, Kyungbuk
  In a road to the PAL-XFEL, the 1st stage will be to build a test machine, whose design parameters are presented here. It will be a 230 MeV machine that has the target wavelength of visible range. The design details and simulation results are shown in this paper.  
 
MOPPH063 Potentialities of ELMI Device for Submillimeter Generation by Stimulated Intercavity Scattering in Planar FEM radiation, scattering, electron, cathode 156
 
  • N. S. Ginzburg, N. Yu. Peskov, A. Sergeev, V. Yu. Zaslavsky, I. V. Zotova
    IAP/RAS, Nizhny Novgorod
  • P. V. Kalinin, S. A. Kuznetsov, A. V. Arzhannikov
    BINP SB RAS, Novosibirsk
  Paper describes main features of a project on two-stage generation of submillimeter radiation at the ELMI device. This novel variant of a two-stage scheme based on stimulated intercavity scattering was proposed earlier in the paper*. In accordance with the scheme, at the first stage a sheet electron beam drives a 2D Bragg free electron maser (FEM) of planar geometry to generate 4-mm pump wave. At the second stage this wave undergoes stimulated scattering at the supplementary electron beam to produce submillimeter radiation. A key feature of a proposed scheme is to use two sheet beams with a few kiloampers currents that transported in parallel channels, which are connected by a special waveguide* for synchronization of beam radiation in different channels**. Production of two sheet beams by one accelerator diode with two cathodes is also similar to the process of operation of the multibeam diode described in Ref.**. Two-stage scheme allows us to use high power 4-mm radiation produced in the first channel by the sheet beam moving in an undulator quasi-static magnetic field, as an EM-undulator for the secondary stage FEL operating in Terahertz wave range. In the paper we describe results of theoretical and experimental investigations of various aspects of the two-stage scheme and some testing experiments on units for realization of this scheme at the ELMI device.

* A. V.Arzhannikov et al. Proc. Int. Workshop, N. Novgorod, Vol.1,p.228-232,2006.** A. V.Arzhannikov et al. Digest Tech. Papers, PPPS-2001, Las Vegas, Nevada, Vol.1, p.561-564,2001.

 
 
MOPPH068 The NCAS-FEL: an FEL Oscillator with High Slippage undulator, electron, radiation, laser 163
 
  • K.-J. Boller, E. van Geijin
    Mesa+, Enschede
  • J. Jalink, W. J. van der Zande
    Radboud University Nijmegen, Institute of Molecules and Materials, Nijmegen
  • P. J.M. van der Slot
    Twente University, Laser Physics and Non-Linear Optics Group, Enschede
  In normal operation of FEL oscillators with little or no slippage, the cavity length needs to be slightly smaller than the synchronous value due to the lethargy in the gain build-up. If the FEL experiences high slippage, i.e., when the slippage becomes comparable or even larger than the length of the electron pulse, a different cavity detuning may be required. We use the one dimensional Medusa1D code to study the NCAS-FEL* as an example of an FEL oscillator having high slippage. Medusa1d is basically equal to the fully three dimensional Medusa code** with the 3D effects stripped out. It includes multiple wiggler segments, electron beam transport elements, harmonics and a simple oscillator model. Medusa1D can also include 3D effects using the fitting formula of Xie***. The NCAS-FEL is a RF-linac based FEL dedicated for high resolution spectroscopic studies in the wavelength range from 100 micron to 1.5 mm. The design of the NCAS-FEL is currently under way, and we report here initial results of this design and focus on the effects of high slippage on cavity detuning and the development of coherence within the optical pulse.

* Proceedings of FEL 2006, Berlin, Germany (2006) p485 - 487 ** Phys. Rev. ST-AB 8, 110701 (2005)*** Nucl. Instrum. Methods Phys. Res., Sect. A 445, 59 (2000)

 
 
MOPPH069 3D Modelling of the ERLP IR-FEL radiation, electron, alignment, wiggler 167
 
  • J. A. Clarke, N. Thompson, D. J. Dunning
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • B. W.J. McNeil
    USTRAT/SUPA, Glasgow
  An Energy Recovery Linac Prototype (ERLP) facility is currently being commissioned at Daresbury Laboratory; it serves as a testbed for technologies to be used in the proposed 4th Generation Light Source (4GLS) facility. As part of the ERLP facility, an infra-red oscillator FEL is due to be commissioned early in 2008. In this paper we present full three dimensional, time-dependent modelling of the ERLP IR-FEL using Genesis 1.3 in combination with a paraxial optical propagation code (OPC). We also discuss how this work will be used to inform commissioning of the FEL.  
 
MOPPH074 Preliminary Design of the Proposed IR-FEL in India electron, undulator, radiation, linac 179
 
  • V. Kumar, S. Krishnagopal
    RRCAT, Indore (M. P.)
  We propose to build a infra-red free-electron laser facility in India. We present details of the preliminary design of the FEL.  
 
MOCAU01 Short Wavelength Regenerative Amplifier FELs feedback, electron, radiation, undulator 182
 
  • D. J. Dunning, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • B. W.J. McNeil
    USTRAT/SUPA, Glasgow
  In this paper we discuss the possibility of extending the operating wavelength range of tunable Regenerative Amplifier FELs to shorter wavelengths than current design proposals, notably into the XUV regions of the spectrum and beyond where the reflectivity of broadband optics is very low. Simulation studies are presented which demonstrate the development of good temporal coherence in generic systems with a broadband radiation feedback of less than one part in ten thousand.  
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MOCAU02 Numerical Solution of the FEL Correlation Function Equation undulator, electron, radiation 188
 
  • N. Vinokurov, O. A. Shevchenko
    BINP SB RAS, Novosibirsk
  The equation for two-particle correlation function in FEL was derived recently to provide a new way of noise calculations in FELs*. In this paper this equation is solved numerically for the simplest case of narrow electron beam. Time independent solution with saturation is obtained. It is compared with the results of quasilinear theory and results of previous SASE linewidth estimates.

* O. A. Shevchenko, N. A. Vinokurov, NIM A507 (2003) 84-88

 
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MOCAU03 Numerical Propagation Simulations and Coherence Analysis of SASE Wavefronts ion 192
 
  • M.-E. Couprie, M. Labat, G. Lambert, O. V. Chubar
    SOLEIL, Gif-sur-Yvette
  • O. Tcherbakoff
    CEA, Gif-sur-Yvette
  Examples of wavefront propagation simulation and coherence analysis of SASE, seeded and started-up from noise, are presented. The calculations are performed using SRW – the wave-optics computer code optimized for synchrotron radiation, and the 3D FEL simulation code GENESIS 1.3. To ensure easy inter-operation and data exchange between the two codes, GENESIS has been integrated into the "emission" part of the SRW, which is dedicated for calculation of initial wavefronts in the form ready for subsequent propagation simulations. In the examples described, after each run of GENESIS in time-dependent mode, the electric field is transformed from time to frequency domain, and the wavefront obtained this way is numerically propagated, using Fourier-optics methods implemented in the SRW, from the exit of the FEL undulator to image plane of a simple interferometer-type optical scheme. Intensity-averaged patterns, obtained after multiple cycles of the SASE (in presence of shot noise and/or a timing jitter) and the wavefront propagation calculations, allow for straightforward characterization of spatial coherence by visibility of interference fringes. SRW code can also be used for complete optimization of optical beamlines for 4th generation synchrotron radiation sources, which require accurate treatment of wave-optical phenomena in the frequency and time domains.  
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TUAAU02 Electron Outcoupling Scheme for the Novosibirsk FEL undulator, electron, radiation, bunching 204
 
  • O. A. Shevchenko, V. G. Tcheskidov, N. Vinokurov, A. N. Matveenko
    BINP SB RAS, Novosibirsk
  One of the main problems of contemporary high power FELs is the mirror heating. One of the possible solutions of this problem is the use of electron outcoupling*. In this case the mirrors of optical resonator are not transparent and the coherent radiation from an additional undulator in the FEL magnetic system is used. To provide the output of this radiation the electron beam in the auxiliary undulator is deflected from the optical resonator axis. To save bunching it is preferable to use the achromatic deflecting bend. The project of electron outcoupling for the Novosibirsk FEL is described. Simulation results are presented.

* N. G. Gavrilov et al., NIM A304 (1991) 63-65

 
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TUAAU05 Modelling Mirror Aberrations in FEL Oscillators Using OPC undulator, laser, free-electron-laser, radiation 207
 
  • K.-J. Boller, J. G. Karssenberg, P. J.M. van der Slot
    Mesa+, Enschede
  Thermal distortion in mirrors used in high average power FEL oscillators, like the JLAB FEL and the 4GLS VUV-FEL, will influence the mode quality and affect the FEL performance. In order to quantify these effects, these distortions needs to be characterised. Mirror aberrations are generally described using Zernike polynomials and also in case of thermal distortions, it has been shown that these polynomials can be used to describe the mirror distortion*. The Optical Propagation Code (OPC)** is a general optical propagation package in the paraxial approximation, that works together with gain codes like Medusa and Genesis 1.3 to model FEL oscillators. We have extended OPC to include phase masks, that can either be generated by an external program or internally using Zernike polynomials. This allows OPC to model mirror aberrations. We will present a few examples, illustrating the capabilities of OPC.

* Nucl. Instrum. Meth. A407 (1998)401** J. Appl. Phys. 100, 093106 (2006)

 
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TUBAU04 Towards a Low Emittance X-ray FEL at PSI emittance, electron, acceleration, cathode 224
 
  • A. Adelmann, A. Anghel, R. J. Bakker, M. Dehler, R. Ganter, C. Gough, S. Ivkovic, F. Jenni, C. Kraus, F. Le Pimpec, S. C. Leemann, K. B. Li, P. Ming, B. S.C. Oswald, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, T. Schietinger, V. Schlott, L. Schulz, A. Streun, F. Stulle, D. Vermeulen, F. Q. Wei, A. F. Wrulich, A. Oppelt
    PSI, Villigen
  The Paul Scherrer Institute (PSI) in Switzerland aims at building a compact and cost-effective X-ray FEL facility for the wavelength range 0.1 - 10 nm. Based on the generation of very low emittance beams, it consists of a low-emittance electron gun (LEG) followed by high-gradient acceleration, and advanced accelerator technology for preserving the initial low emittance during further acceleration and bunch compression. In order to demonstrate the feasibility of the concept and the emittance preservation, a 250 MeV test facility will be built. This machine has been designed to be used as injector for the X-ray FEL at a later date. The accelerator design of the 250 MeV linac will be presented in the paper together with the status of the LEG and high gradient acceleration.  
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TUPPH006 FEL Potential of the High Current ERLs at BNL electron, emittance, linac, gun 232
 
  • I. Ben-Zvi, V. Litvinenko, E. Pozdeyev, D. Kayran
    BNL, Upton, Long Island, New York
  An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under construction at Brookhaven National Laboratory (BNL)* for testing concepts for high-energy electron cooling and electron-ion colliders. This ERL prototype will be used as a test bed to study issues relevant for very high current ERLs. High average current and high performance of electron beam with some additional components make this ERL an excellent driver for high power far infrared Free Electron Laser (FEL). A possibility for future up-grade to a two-pass ERL is considered. We present the status and our plans for construction and commissioning of the ERL. We discus a FEL potential based on electron beam provided by BNL ERL.

* Litvinenko, V. N. et al. High current energy recovery linac at BNL. Proc. 26th International Free Electron Laser Conference and 11th FEL Users Workshop (FEL 2004).

 
 
TUPPH008 Beam Dynamics Studies on the UVSOR-II Free Electron Laser laser, electron, injection, synchrotron 236
 
  • M.-E. Couprie
    SOLEIL, Gif-sur-Yvette
  • M. Hosaka
    Nagoya University, Nagoya
  • M. Katoh, A. Mochihashi, M. Shimada
    UVSOR, Okazaki
  • G. Lambert
    RIKEN Spring-8, Hyogo
  • M. Labat
    CEA, Gif-sur-Yvette
  In the Coherent Harmonic Generation Free Electron Laser configuration, an external laser source is seeded inside a first undulator. The interaction between the electron beam and this seed induces energy modulation of the bunch, further converted into a density modulation, producing coherent radiation in a second undulator. The energy modulation enhances the energy spread of the electron bunch, converted by the machine optics into a modification of its longitudinal distribution. In the case of a storage ring FEL, the electrons are re-circulating: the same bunch keeps interacting with the seeded laser, and relaxation of the distribution is only allowed in between two laser injections. Such specific dynamics has been studied on the CHG FEL of UVSOR-II storage ring (Japan). The electron beam stored at 600 MeV is seeded using a 2.5 mJ, 1 kHz, 1.2 ps Ti:Sa laser at 800 nm wavelength, allowing radiation at 266 nm (third harmonic). A Streak Camera is used to record the evolution of the longitudinal profiles as a function of the repetition rate and average power of the seeding laser, leading to bunch lengthening and distortion dynamical analysis. It appeared that because the heating induced by the interaction remains local, the refreshment process of the electronic distribution is modified. The experimental results are compared to simulations using SYNC.  
 
TUPPH013 Production of Ultra-short Radiation Pulses in Frequency Doubler undulator, electron, radiation, laser 248
 
  • E. Schneidmiller, M. V. Yurkov, E. Saldin
    DESY, Hamburg
  Typically beam formation system of driver linac for SASE FEL produces electron beams with small local energy spread. This feature opens up extra possibilities for implementation of different FEL schemes. One of them is an effective frequency doubler*. It consists of an undulator tuned to the fundamental harmonic, dispersion section, and undulator tuned to the second harmonic. The first stage is a conventional soft X-ray SASE FEL. Its gain is controlled in such a way that the maximum energy modulation of the electron beam at the XFEL exit is about equal to the local energy spread, but still far away from saturation. When electron bunch passes through dispersion section this energy modulation leads to effective compression of the particles. Then bunched electron beam enters the 2nd harmonic undulator, and produces the radiation at the 2nd harmonic. Recently SASE FEL FLASH in Hamburg demonstrated unique mode of operation generating sub-10-fs radiation pulses**. In this paper we study an option of frequency doubler for FLASH operating in the femtosecond mode of operation.

* J. Feldhaus et al., NIM A 528 (2004) 471.** W. Ackermann et al., "Operation of a free electron laser from the extreme ultraviolet to the water window", Nature Photonics, in press.

 
 
TUPPH014 Generation of X-ray FEL Light Using Laser Wakefield Accelerated Electron Beams undulator, electron, laser, radiation 252
 
  • A. Rousse, K. Ta Phuoc
    LOA, Palaiseau
  • N. Vinokurov, O. A. Shevchenko
    BINP SB RAS, Novosibirsk
  We consider a new class of high gain FELs based on femtosecond electron bunches with extra high current density produced by Laser Wake Field Acceleration (LWFA). The FELs of this kind can be used for generation of high power femtosecond x-ray pulses. We present the results of simulations of FEL operation with some reasonable beam parameters which will be obtained in future. We focus our attention on the advantages which can be gained from the unique possibility of the use of femtosecond hundred-kiloamperes bunches, generated by LWFA. We also consider the impact of the relatively poor electron beam properties on FEL characteristics.  
 
TUPPH019 Simulations for the LCLS Injector emittance, laser, cathode, gun 260
 
  • Y. T. Ding, D. Dowell, P. Emma, J. C. Frisch, A. Gilevich, G. R. Hays, P. Hering, Z. Huang, R. H. Iverson, P. Krejcik, H. Loos, A. Miahnahri, J. F. Schmerge, J. L. Turner, W. E. White, J. Wu, C. Limborg-Deprey
    SLAC, Menlo Park, California
  The commissioning of the LCLS Injector has started this year. The electron beam quality for producing high power SASE X-rays is very challenging to reach. In this paper, we will describe comparisons between simulations made with multi-particle tracking code and electron beam measurements performed on the LCLS injector.  
 
TUPPH020 Quiet Start Method in small signal HGHG FEL Simulation bunching, electron, laser, resonance 264
 
  • Y. Hao, Y. Hao
    IUCF, Bloomington, Indiana
  • L.-H. Yu
    BNL, Upton, Long Island, New York
  Quiet start scheme is broadly utilized in Self Amplified Spontaneous Radiation (SASE)FEL simulations, which is proven to be correct and efficient. Nevertheless, due to the energy modulation and dispersion section, the High Gain Harmonic Generation (HGHG) FEL simulation will not be improved by the traditional quiet start method. A new approach is presented to largely decrease the number of macro-partilces per slice that can be implemented in both time-independent and time-dependent simulation, accordingly expedites the high order harmonic cascade simulation or other small signal HGHG cases.  
 
WEAAU02 Direct Measurement of Phase Space Evolution in the SPARC High Brightness Photoinjector emittance, laser, brightness, gun 284
 
  • D. Alesini, M. Bellaveglia, M. Boscolo, M. Castellano, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, M. Ferrario, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, M. Incurvati, C. Ligi, L. Pellegrino, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, F. Tazzioli, S. Tomassini, C. Vaccarezza, M. Vescovi, C. Vicario, E. Chiadroni
    INFN/LNF, Frascati (Roma)
  • A. Bacci
    INFN/LASA, Segrate (MI)
  • L. Catani, A. Cianchi
    INFN-Roma II, Roma
  • S. Cialdi, A. R. Rossi, L. Serafini
    INFN-Milano, Milano
  • L. Giannessi, M. Quattromini, C. Ronsivalle
    ENEA C. R. Frascati, Frascati (Roma)
  • M. Migliorati, A. Mostacci, L. Palumbo
    Rome University La Sapienza, Roma
  • P. Musumeci, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • M. Petrarca
    INFN-Roma, Roma
  The characterization of the transverse phase space for high charge density relativistic electron beams is a fundamental requirement in many particle accelerator facilities, in particular those devoted to fourth-generation synchrotron radiation sources, such as SASE FEL. The main purpose of the SPARC initial phase was the commissioning of the RF photoinjector. At this regard, the evolution of the phase space has been fully characterized by means of the emittance meter diagnostics tool, placed in the drift after the gun exit. The large amount of collected data has shown not only that we can achieve the SPARC nominal parameters, but has also allowed for the first time a detailed reconstruction of the transverse phase space evolution along the drift, giving evidences of the emittance compensation process to occur as predicted by theory and simulations. In particular the peculiar behavior of a flat top longitudinal electron distribution compared to a gaussian distribution has been studied giving important insights for the correct matching with the following linac based on the double emittance minimum effect.  
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WEBAU04 Single-Shot Longitudinal Bunch Profile Measurements at FLASH Using Electro-Optic Detection: Experiment, Simulation, and Validation laser, electron, polarization, linac 310
 
  • V. R. Arsov, E.-A. Knabbe, B. Schmidt, P. Schmüser, B. Steffen
    DESY, Hamburg
  • G. Berden, A. F.G. van der Meer
    FOM Rijnhuizen, Nieuwegein
  • W. A. Gillespie, P. J. Phillips
    University of Dundee, Nethergate, Dundee, Scotland
  • S. P. Jamison
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • A. MacLeod
    UAD, Dundee
  At the superconducting linac of FLASH at DESY, we have installed an electro-optic experiment for single shot, non-destructive measurements of the longitudinal electric charge distribution of individual electron bunches. The profile of the electric bunch field is electro-optically encoded onto a stretched Ti:Sa laser pulse. In the decoding step, the profile is retrieved from a cross-correlation of the encoded pulse with a 35 fs laser pulse, obtained from the same laser. At FLASH, sub-100 fs electron bunches have been measured during FEL operation with a resolution of better than 50 fs. The electro-optic encoding process in gallium phosphide as well as the decoding step in a frequency doubling BBO crystal were numerically simulated using bunch shapes simultaneously measured with a transverse-deflecting rf structure as input data. In this contribution, we present electro-optically measured profiles and compare them with the simulation.  
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WEPPH003 Magnetic Measurements of the FLASH Infrared Undulator undulator, radiation, electron, power-supply 318
 
  • A. Chesnov, E. A. Matushevsky, D. Petrov, E. Syresin, N. A. Morozov
    JINR, Dubna, Moscow Region
  • O. Grimm, Y. Holler
    DESY, Hamburg
  • J. Rossbach
    Uni HH, Hamburg
  The FLASH free-electron laser at DESY, Hamburg, will be equipped with an infrared electromagnetic undulator during the current shut-down, providing radiation in the range 1-200 um. It will be used both for electron beam diagnostics purposes and as a powerful source synchronized to the VUV and soft X-ray pulses of the FEL. The undulator was constructed at the Joint Institute of Nuclear Research (JINR). This paper summarizes the extensive magnetic measurements that where performed both at JINR and DESY prior to installation of the undulator.  
 
WEPPH006 Study of Undulator Deformation Tolerance for the European XFEL undulator, radiation, electron, photon 330
 
  • B. Faatz, J. Pflueger, Y. Li
    DESY, Hamburg
  The undulators for the European XFEL use NdFeB type permanent magnets. Even for perfect magnet material, the undulator quality degrades due to mechanical limitations, such as girder deformation, and temperature variation. Since the beam orbit can always be corrected, the main effect will be a variation in slippage between electrons and photon beam along the undulator. A careful estimation of the error budget is needed to avoid cost driving hardware efforts. We modeled deformation, gap variation and temperature error and used GENESIS to simulate the effect on the performance of the European XFEL.  
 
WEPPH009 Recent Measurements of the Longitudinal Phase Space at PITZ gun, booster, electron, emittance 342
 
  • G. Asova, J. W. Baehr, C. H. Boulware, H.-J. Grabosch, L. H. Hakobyan, M. Hänel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, S. Lederer, B. Petrosyan, S. Riemann, S. Rimjaem, T. A. Scholz, L. Staykov, F. Stephan
    DESY Zeuthen, Zeuthen
  • R. Richter
    BESSY GmbH, Berlin
  • K. Rosbach
    Humboldt University Berlin, Institut für Physik, Berlin
  • J. Rossbach, J. Roensch
    Uni HH, Hamburg
  The Photo Injector Test facility at DESY in Zeuthen (PITZ) was built to test and optimize electron guns for short wavelength Free-Electron Lasers (FELs) like FLASH and XFEL at DESY in Hamburg. For a detailed analysis of the behaviour of the electron bunch, the longitudinal phase space and it projections can be measured behind the gun cavity. The electric field at the photo cathode was increased from 40 MV/m to 60 MV/m, to optimize the transverse emittance. The momentum distributions for different gradients and gun phases will be presented. The determination of the field balance from the momentum distribution will be discussed. In order to study emittance conservation, a booster cavity and additional diagnostics were installed. The evolution of the longitudinal phase space in the booster cavity will be investigated. Measurements of the momentum distribution and longitudinal distribution behind the booster cavity will be discussed.  
 
WEPPH027 Beam Diagnostics for the First Lasing of the KU-FEL gun, electron, emittance, undulator 402
 
  • T. Kii, K. Masuda, H. Ohgaki, S. Sasaki, T. Shiiyama, H. Zen
    Kyoto IAE, Kyoto
  Mid-IR FEL (4-13μm) device for energy science has been constructed in Institute of Advanced Energy, Kyoto University and the electron beam of 40MeV has been successfully accelerated*. The transverse phase space distribution and the corresponding emittance of the electron beam were measured by using a tomographic method**. As the result, normalized emittance was around 3 pi mm mrad. An FEL gain calculation*** shows that the peak current of 10A is the minimum value for the FEL amplification, and that of 40A is required to achieve the FEL saturation. Therefore the bunch compression experiment has been carried out to shorten the micro-bunch length by 2 ps in KU-FEL. The 180 deg. arc section was used for the bunch compression. We will report the result of the emittance measurement and of the bunch compression experiment in the conference.

* H. Ohgaki, et al., NIM A, vol.528, pp.366-370 (2004).** H. Zen, et al., Proc. of the FEL 2006, pp.592-595(2006)*** M. Nakano, et al., Proc. of the FEL 2006, pp.660-664 (2006).

 
 
WEPPH031 Development of A Low Emittance DC Gun for Smith-Purcell BWO FEL emittance, gun, cathode, electron 417
 
  • K. Akiyama, H. Hama, F. Hinode, M. Kawai, T. Muto, K. Nanbu, T. Tanaka, M. Yasuda, K. Kasamsook
    Tohoku University, School of Scinece, Sendai
  An electron DC gun capable for producing very low emittance beam is under developed at Laboratory of Nuclear Science, Tohoku University. The DC gun employs a high voltage of 50 kV to extract electrons, which is suitable to drive Smith-Purcell backward wave oscillator free electron laser (BWO FEL). A result of numerical simulation using a 3-D finite deference time domain (FDTD) method shows the BWO FEL oscillation at the terahertz wavelength region maybe achieved by using the electron beam with an emittance around 0.1 mmmrad. Average power is expected to be more than 100 W per square mm. In addition to which a very small cathode of LaB6 single crystal is employed for the gun, the geometrical structure is optimized to produce the lower emittance beam. A numerical calculation of the elctro-static model for the DC gun to solve equilibrated beam envelope predicts a normalized beam emittance of 0.2 mmmrad will be realized at the beam current of a couple of hundreds mA. Particularly by applying special bias voltage between the cathode and the wehnelt, the transverse distribution of electrons is possibly becoming to be an ideal Kapchinskij-Vladimirskij (K-V) beam, so that the space charge effect will be minimized. The paper will present the status of the development of the low emittance DC gun and various simulation result of the terahertz BWO FEL oscillation.  
 
WEPPH032 Electron-Linac Based Femtosecond THz Radiation Source at PAL radiation, electron, linac, target 421
 
  • J. Choi, Y. G. Jung, C. Kim, H.-G. Kim, S.-C. Kim, I. S. Ko, W. W. Lee, B. R. Park, H. S. Suh, I. H. Yu, H.-S. Kang
    PAL, Pohang, Kyungbuk
  A 60-MeV electron linac for intense femto-second THz radiation is under construction at PAL, which is the beamline construction project to be completed by 2008. To get intense femto-second THz radiation up to 100 cm-1, the electron beam should be compressed down to below 100 fs. The linac will use an S-band photocathode RF-gun as an electron beam source, two S-band accelerating structures to accelerate the beam to 60 MeV, a chicane-type bunch compressor to get femto-second electron bunch, and an optical transition radiation (OTR) target as a radiator. The PARMELA code simulation result shows that the 0.2 nC beam can be compressed down to a few tens of femto-seconds, and even the higher charge of 0.5nC to about one hundred femto-seconds. Also, the linac will be able to provide a femto-second electron beam for electron pulse radiolysis and compton-scattering experiment for fs X-ray.  
 
WEPPH039 The Optical Replica Synthesizer in FLASH laser, undulator, electron, vacuum 438
 
  • G. Angelova, V. G. Ziemann
    UU/ISV, Uppsala
  • J. Boedewadt, S. Khan, A. Winter
    Uni HH, Hamburg
  • A. Meseck
    BESSY GmbH, Berlin
  • E. Saldin, H. Schlarb, B. Schmidt, E. Schneidmiller, M. V. Yurkov
    DESY, Hamburg
  • P. M. Salen, P. van der Meulen
    FYSIKUM, AlbaNova, Stockholm University, Stockholm
  During the shutdown in spring 2007 the optical replica synthesizer, a novel device to diagnose ultra-short electron bunches, is assembled in the FLASH accelerator. We report on the status of the construction work with emphasis on the two electro-magnetic undulators needed for micro-bunching and replica-pulse generation.  
 
WEPPH054 Coherent THz Light Source Using Very Short Electron Bunches from a Thermionic RF Gun gun, electron, undulator, radiation 476
 
  • K. Akiyama, H. Hama, F. Hinode, K. Kasamsook, M. Kawai, K. Nanbu, T. Tanaka, M. Yasuda, T. Muto
    Tohoku University, School of Scinece, Sendai
  To develop a narrowband coherent Terahertz (THz) light source, a project for producing very short electron bunch has been progressed at Laboratory of Nuclear Science, Tohoku University. Coherent synchrotron radiation is another promising source for generation of high-power THz light. Passing through a conventional undulator with a field period length of ~ 10 cm, the very short electron bunch at the energy around 15 MeV can produce coherent THz radiation. The electron beams of which the bunch length is less than 100 femto-second will be generated by a combined injector system of a thermionic RF gun and a bunch compressor. We have developed an independently-tunable-cells (ITC) RF gun consisted with two uncoupled cavities in order to manipulate the longitudinal phase space. It was found out that the ITC-RF gun is possibly quite suitable to produce such a very short bunch employing a magnetic bunch compressor. In theoretical investigation at the moment, a bunch length of less than 50 fs has been achieved in the numerical tracking simulation. Employing Lienard-Weichert potential, we have performed a 3-D simulation of the coherent THz radiation. The paper will describes the latest status of development of the ITC RF gun and tracking simulations for the bunch compressor as well. Characteristics of the coherent THz radiation resulted from the simulation will be also reported  
 
WEPPH058 Modeling a RF Linac Based Short Pulse Waveguide FEL radiation, electron, interaction-region, bunching 487
 
  • Y. Pinhasi, Yu. Lurie
    CJS, Ariel
  • M. Tecimer
    NHMFL, Tallahassee, Florida
  We discuss modeling a highly slippage dominated short pulse, long wavelength rf linac based THz FEL in a waveguide cavity.  
 
FRAAU03 Compact Ring FEL as a Source of High Power Infrared Radiation radiation, undulator, electron, bunching 517
 
  • A. N. Matveenko, N. Vinokurov, O. A. Shevchenko
    BINP SB RAS, Novosibirsk
  Ring FELs* were proposed mainly to improve the quality of radiation of x-ray FELs. Their main advantage is the absence of mirrors. It appears that this advantage is also useful for high power FELs. Another reason to build infrared ring FEL is the proof-of-principle for shorter wavelength FELs. Therefore we considered the scheme of infrared ring FEL which requires ERL with beam energy 50 MeV. Using extensive simulations we developed requirements for electron beam parameters and magnetic system of ring FEL. In spite of rather compact design such FEL may provide more than 10 kW average power.

* N. A. Vinokurov, O. A. Shevchenko, NIM A528 (2004) 491-496

 
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