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

laser

Paper Title Other Keywords Page
MOPPH003 VOLC: Volume Free Electron Laser Simulation Code electron, simulation, radiation, free-electron-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.

 
 
MOPPH010 Three-Dimensional Analysis of the Surface Mode Supported by a Reflection Grating electron, electromagnetic-fields, polarization, free-electron-laser 38
 
  • K.-J. Kim
    ANL, Argonne, Illinois
  • V. Kumar
    RRCAT, Indore (M. P.)
  In a Smith-Purcell Free-Electron Laser (SP-FEL), the electron beam interacts with the surface mode supported by a metallic reflection grating to produce coherent radiation. All the previous analyses of SP-FEL had considered the localization of the surface mode only in the direction perpendicular to the grating surface and assumed translational invariance along the direction of grooves of the grating. In this paper, we include the localization of the surface mode along the direction of grooves and study the three-dimensional structure of the surface mode in order to include diffraction effects in the analysis of SP-FELs. Full three-dimensional Maxwell-Lorentz equations are derived for the self-consistent nonlinear analysis of SP-FELs.  
 
MOPPH012 Conservation Laws in Quasilinear Theory of Raman Free-Electron Laser electron, space-charge, plasma, free-electron-laser 46
 
  • A. Chakhmachi
    AEOI, Tehran
  • B. Maraghechi
    AUT, Tehran
  A quasilinear theory of the free-electron laser, in Raman regime, is presented to establish that conservation laws on number, energy, and momentum are upheld. A high density electron beam is assumed so that the space-charge potential is no longer negligible. A sufficiently broad band spectrum of waves is assumed so that saturation will be due to the quasilinear spread of the beam electrons. Otherwise, for the single mode excitation, saturation will be due to the electron trapping in the space-charge potential. It is shown that the quasilinear slow variation of the background distribution function is in the form of the diffusion equation in momentum space. An expression for the time evolution of the spectral energy density is derived. Conservation laws to the quasilinear order (second order) are derived and are proved to be satisfied. Results of the present investigation may be used to study the quasilinear saturation of free-electron laser in the presence of the space-charge wave.  
 
MOPPH015 Limit for Harmonic Conversion in a Single Cascade of Coherent Harmonic Generation bunching, electron, radiation, simulation 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.

 
 
MOPPH017 1D Linear Intensity Spiking Evolution in a Single Shot of a SASE FEL radiation, electron, undulator, free-electron-laser 54
 
  • V. Petrillo
    Universita' degli Studi di Milano, Milano
  • L. Serafini, C. Maroli
    INFN-Milano, Milano
  The analysis is based on the 1D Maxwell-Lorentz equations which are reduced to the usual averaged linear equation in the limit of vanishingly small radiation field A(z,t) and average length lm. It is shown that if this equation is solved with initial shot noise conditions in which the widths of the spikes and the average distance between successive spikes are both uniformly smaller than the cooperation length Lc, it may lead to large amplitude coherent signals. The intensity spiking RMS relative amplitude decreases from the 100% values it has at t=0, down to values of the order or less than 0.1% in time intervals from ten to twenty gain times.  
 
MOPPH019 Optimized Designs for CAEP IR Free-electron Laser coupling, simulation, free-electron-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.  
 
MOPPH025 Three-dimensional Theory of the Cerenkov Free-Electron Laser electron, free-electron-laser, radiation, feedback 73
 
  • C. A. Brau, H. L. Andrews
    Vanderbilt University, Nashville, Tennessee
  We present an analytical theory for the operation of a Cerenkov free-electron laser which includes diffraction of the optical mode in the direction transverse to the electron beam. Because the width of the optical mode depends on the gain, the usual cubic dispersion relation is replaced by a 5/2-power dispersion relation, however, only two of these roots are allowed. These two roots both have positive real parts, indicating that they are slow waves. For a narrow electron beam, the optical mode is much wider than the beam, thus reducing the gain by an order of magnitude from that predicted by the two dimensional theory. In the limit of a wide electron beam, the two dimensional theory is recovered.  
 
MOPPH026 Three-Dimensional Theory of the Smith-Purcell Free-Electron Laser electron, free-electron-laser, radiation, synchrotron 77
 
  • H. L. Andrews, C. A. Brau, J. D. Jarvis
    Vanderbilt University, Nashville, Tennessee
  We present an analytic theory for the operation of a Smith-Purcell free-electron laser (SPFEL) that includes transverse diffraction of the optical beam. For the case of an infinitely wide electron beam, this theory agrees with previous two-dimensional analyses. When the electron beam is narrow compared to the mode, the gain (amplifier regime) is substantially reduced by diffraction, while its dependence on the beam current is increased due to gain guiding. A 5/2-power dispersion relation replaces the conventional cubic dispersion relation. Additionally, the constituent waves of the laser mode are found to have different transverse decay rates. An estimate of the start current (oscillator regime) of the device is obtained by satisfying the appropriate boundary conditions on the beam axis.  
 
MOPPH028 On NMR probing of the kinetics of a free-electron laser-induced chemical exchange resonance, free-electron-laser 81
 
  • S. P. Babailov
    Nikolaev IIC, Novosibirsk
  Determination of the quantum yields of photochemical reactions (in particular, molecular photoisomerization reactions) is an efficient application of NMR spectroscopy*,**. We are proposed a combined approach for study the kinetics of photo-induced chemical exchange (PICE) reactions (see Scheme), which involves a free-electron laser (FEL) and NMR spectroscopy**. Scheme hv A↔B Continuous and pulse IR-irradiation of the chemical system in the presence of PICE can be achieved using FEL. Based on the analytical equations derived in the work we consider the time-dependent dynamics of variation of the instant NMR line shape for two-site chemical exchange. If one induce an abrupt increase in the rate constant of chemical exchange (for example, by quickly heating the system or PICE), then the NMR line shape will change with time, ultimately reaching another new steady state. Our calculations show that there are beats and oscillations (on the NMR line shape) damped with time. The information about the time-dependent instant line shapes provides possibility to predict the real kinetics of PICE. Prospective objects are molecular conformers and spin isomers. So, FEL can be used in the setup for PICE studies in combination with a NMR spectrometer.

* S. P. Babailov, E. M. Glebov, et al., Concepts in Magn. Reson., 2006, 8, 571. ** S. P. Babailov, Russ. Chem. Bull., Int. Ed., 2006, 10, 1631.

 
 
MOPPH030 Terahertz Imaging and Radioscopy with 160x120 Microbolometer 90 fps Camera radiation, free-electron-laser, electron, controls 83
 
  • A. L. Aseev, M. A. Dem'yanenko, D. G. Esaev, I. V. Marchishin
    ISP, Novosibirsk
  • G. N. Kulipanov, N. Vinokurov, B. A. Knyazev
    BINP SB RAS, Novosibirsk
  Uncooled micromolometer camera for IR and THz high-speed imaging has been developed. The 160x120 focal plane array consists of resistive vanadium oxide elements on a silicon nitride bridge. The element size is 48x48 micron at 51 micron array period. We describe device fabrication process and focal plane array operational characteristics. The camera was used as a recorder in quasi-optical systems with Novosibirsk terahertz free electron laser as a radiation source. Radioscopy of the objects, which are of interest for biology and security applications, has been demonstrated. The recording rate up to 90 frames per second has been obtained.  
 
MOPPH031 Spectroscopy and Spectrally Resolved Radioscopy of Biological Substances Using Terahertz Free Electron Laser Radiation radiation, free-electron-laser, diagnostics, electron 86
 
  • V. V. Gerasimov
    NSU, Novosibirsk
  • A. M. Gonchar
    ICG SB RAS, Novosibirsk
  • B. A. Knyazev
    BINP SB RAS, Novosibirsk
  High average power and monochromacity of terahertz Novosibirsk free electron laser are favorable for the development of time and space resolved spectroscopic and radioscopic techniques for study of highly absorbing substances, in particular, biological ones. To study highly absorbing objects we applied a homemade attenuated total reflection spectrometer, which enables operation in both conventional and imaging mode. By measuring the reflection coefficients for p- and s-polarized radiation, the real (n) and imaginary (k) parts of refractive index can be derived. Using a microbolometer matrix (see the paper by Esaev et al. at this conference), imaging radioscopy of the samples containing amino acids and DNA had been performed. The methods developed were applied also for examination of bones of intact and senescence-accelerated mice that, probably, would lead to study osteoporosis development.  
 
MOPPH032 Development of Metal Mesh Based Quasi-optical Selective Components and Their Application in High-power Experiments at Novosibirsk Terahertz FEL radiation, synchrotron, controls, synchrotron-radiation 89
 
  • B. G. Goldenberg, P. V. Kalinin, V. V. Kubarev, N. Vinokurov, S. A. Kuznetsov
    BINP SB RAS, Novosibirsk
  Successful realization of terahertz research programs at the Novosibirsk FEL-facility requires detailed development, designing and optimization of passive quasi-optical selective components, intended for polarization and frequency gating of powerful THz-beams of NovoFEL radiation. Along with desired selective characteristics such components should be capable of operating over a long period of time under high-power load conditions (a few hundred Watts of average incident radiation power) without noticeable degradation of their properties. It admits to employ in selective components only low absorbing and thermostable materials, such as high conductivity metals and special types of polymers. This report is devoted to development of metal mesh based selective structures, such as polarizing beamsplitters (attenuators) and different frequency filters, and their application in high-power THz-experiments. Possibilities and prospects of two main production technologies are discussed: 1) conventional photolithography destined for manufacturing thin metal structures deposited on low-absorbing thermostable polymer films; 2) LIGA-technique intended for producing thick substrate-free metal structures.  
 
MOPPH033 Diffraction Optical Elements and Optical Systems with a High Power Monochromatic Terahertz Source radiation, focusing, free-electron-laser, electron 93
 
  • H. J. Cha, Y. U. Jeong
    KAERI, Daejon
  • V. S. Cherkassky, L. A. Merzhievsky, S. A. Zhigach
    NSU, Novosibirsk
  • A. V. Fanova, B. A. Knyazev, G. N. Kulipanov, N. Vinokurov, I. A. Polskikh
    BINP SB RAS, Novosibirsk
  We have developed reflective diffraction optical elements (DOE) for focusing radiation of terahertz free electron lasers (FEL). Metal-dielectric Fresnel zone plates and metallic kinoform "lenses" were fabricated and tested using FEL radiation. A microbolometer camera (see the paper by Esaev et al. at this conference) sensitive to THz radiation had been applied for recording both terahertz beam caustic and terahertz images. Diffraction efficiency of a kinoform lens appears to be about unity. Quality of images obtained with the kinoform lens was studied. The lens was used as a key element for a Toepler optical system, which were used for studying condense matter non-uniformities and deformations. The experiments were performed at Novosibirsk and KAERI FELs.  
 
MOPPH034 Diagnostics of an Electron Beam using Coherent Cherenkov Radiation radiation, electron, diagnostics, undulator 95
 
  • R. Tikhoplav
    UCLA, Los Angeles, California
  A comparison of coherent Cherenkov and transition radiations as a diagnostic tool for longitudinal distribution of an electron beam is studied in this paper. Two methods will be used for the 7th harmonic bunching experiment at Neptune linear accelerator facility at UCLA. Coherent Cherenkov radiation is produced in an aerogel with an index of refraction close to unity.  
 
MOPPH036 First Experiences with the FIR-FEL at ELBE electron, undulator, radiation, free-electron-laser 97
 
  • P. Michel, W. Seidel, G. Staats, J. Teichert, R. Wuensch, U. Lehnert
    FZD, Dresden
  We show the design and the parameters of operation of the long-wavelength (U100) FEL of ELBE. First lasing has been shown in August, 2006. Since then, the laser has undergone thorough commissioning and is available for user experiments since fall, 2006. Besides in-house users the IR beam is available to external users in the FELBE (FEL@ELBE) program witch is a part of the integrated activity on synchrotron and free electron laser science in the EU. At the beginning of 2007 lasing in the full designed wavelength range from 20μm to 200μm was demonstrated. The laser power typically reaches several W in CW operation but drops for very long wavelengths depending on the size of the used outcoupling hole. However, there exists a serious problem with small gaps in the providable wavelength spectrum. We attribute this behaviour to the transmission characteristics of the overmoded partial waveguide used from the undulator entrance to the first mirror.  
 
MOPPH040 A Study of Detection Schemes in Electro-Optic Sampling Technique electron, diagnostics, background, polarization 101
 
  • J. Y. Huang, C. Kim, I. S. Ko, Y. W. Parc
    PAL, Pohang, Kyungbuk
  Electro-Optic Sampling (EOS) is the ingenious tool for the measurement of the electron beam or Thz radiation. There are two traditional detection schemes: one is the crossed polarizer scheme and another is balanced detection one. A new detection scheme called Near Crossed Polarizer scheme in the EOS technique is developed to increase the Signal to Noise Ratio in the experiment. The new detection scheme is studied in detail and the 3D scanning result with electron beam in FLASH is compared with the detection scheme. The new detection scheme has an analytical problem which shows two solutions for the relative phase shift for specific measurement of the electron beam. That problem is also studied through the comparative study between simulation and the analyzed data from the TEO setup in FLASH.  
 
MOPPH041 Comparative Study of Electro-Optic Effect between Simulation and Measurement electron, simulation, 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.  
 
MOPPH042 Losses in Optical Resonator of Novosibirsk Terahertz Free Electron Laser: Theory and Experiment coupling, electron, free-electron-laser, radiation 107
 
  • V. V. Kubarev
    BINP SB RAS, Novosibirsk
  Design of optical resonator of Novosibirsk terahertz free electron laser (NovoFEL)was made on base simple analitical theory discribed in paper*. Direct comparison of the theory and many experiments on NovoFEL is presented.

* Kubarev V. V. Babinet principle and diffraction losses in laser resonators. Quantum Electronics 30(9)824-826(2000).

 
 
MOPPH050 Status of the Undulator System of the Seeded HGHG-FEL Test Bench at MAX-lab electron, radiation, undulator, simulation 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, simulation 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.  
 
MOPPH052 Output Performance of the STARS HGHG Demonstrator at BESSY undulator, radiation, emittance, electron 130
 
  • K. Goldammer, A. Meseck, B. C. Kuske
    BESSY GmbH, Berlin
  BESSY is planning to construct a free-electron laser facility (STARS) to demonstrate cascaded high-gain harmonic generation (HGHG) FELs. A 325MeV superconducting linear accelerator will drive two HGHG-stages, where the second stage is seeded by the radiation from the first stage. Such a cascading of the HGHG scheme, originally pioneered by L. H. Yu, allows a reduction of the STARS output wavelength down to the few 10nm range. This paper describes the expected performance of the facility, the achievable wavelength range, the harmonic content of the radiation, the potential of super-radiant pulses and first considerations about the stability of the source.  
 
MOPPH055 Measurements of the Projected Normalized Transverse Emittance at PITZ emittance, gun, booster, cathode 138
 
  • G. Asova, K. Boyanov, I. Tsakov
    INRNE, Sofia
  • J. W. Baehr, C. H. Boulware, H.-J. Grabosch, L. H. Hakobyan, M. Hänel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, S. Lederer, A. Oppelt, B. Petrosyan, S. Riemann, S. Rimjaem, J. Roensch, A. Shapovalov, F. Stephan, L. Staykov
    DESY Zeuthen, Zeuthen
  • K. Floettmann
    DESY, Hamburg
  • R. Richter
    BESSY GmbH, Berlin
  The main objective of the Photo Injector Test facility at DESY in Zeuthen (PITZ) is the production of electron beams with minumum transverse emittance at 1 nC bunch charge. PITZ consists of a photo cathode RF gun, solenoids for the compensation of space charge induced emittance growth and a booster cavity. In order to study the emittance evolution along the beam line three Emittance Measurement SYstems (EMSY's) were installed downstream of the booster cavity. In a first operation periode in October 2006 the emittance was measured for moderate gun gradients of about 40 MV/m. A new gun cavity is presently installed at PITZ and conditioning up to a gradient of 60 MV/m is ongoing. In this work we present recent results from measurements of the normalized projected transverse emittance of the electron beam. The emittance is measured using the so called single slit technique. Data are presented for different gun and booster gradients, solenoid strengths and initial beam size at the cathode.  
 
MOPPH060 The Drive Laser System for CFEL feedback, electron, gun, radio-frequency 146
 
  • Y. C. Chen, W. Li
    CAEP/IAE, Mianyang, Sichuan
  A reliable and compact drive system is one of the key components for the stable operation of FEL. We have developed a solid-state drive laser system to meet the requirements of the CFEL(CAEP FEL) research. The system consisted of a passive mode-locked oscillator with a timing stabilizer,a regenerative amplifier and a frequency conversion part. After the 4-th harmonics,the duration of 15 picoseconds Gaussian pulses with wavelength 266nm at a repetition rate 54.17MHz were obtained. These micropulses were contained within a macropulses envelope as long as 1 to 6μmicroseconds,which was emitted from the drive laser at a repetition rate at 3Hz,6Hz or 12Hz,one single micropulse energy as large as 4μmicroJoules was achieved. The design specifications, configuration and diode-pumped amplifier of the drive laser system are also described.  
 
MOPPH068 The NCAS-FEL: an FEL Oscillator with High Slippage undulator, electron, radiation, simulation 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)

 
 
MOPPH072 The IR-Beam Transport System from the ELBE-FELs to the User Labs diagnostics, electron, radiation, focusing 171
 
  • M. Justus, K.-W. Leege, D. Proehl, R. Schlenk, A. Winter, D. Wohlfarth, R. Wuensch, W. Seidel
    FZD, Dresden
  In the Forschungszentrum Dresden-Rossendorf, two free-electron lasers (FELs) have been put into operation. They produce laser light in the medium and the far infrared wavelength range (4-200 microns). The IR light is transported to several laboratories in the same building and to the adjacent building of the High Magnetic Field Laboratory (HLD) as well. The latter is up to 70m away from the FELs. Constructional peculiarities, the large wavelength range (a factor of 50 between the shortest and the longest wavelengths), the high average power in cw regime, and the beam property requirements of the users pose a challenge to the beam line design. The transport system includes vacuum pipes, plane and toroidal gold-covered copper mirrors, exit windows, and diagnostic elements. The designed transport system produces a beam waist at selected spots in each laboratory representing an image of the outcoupling hole. Spot size and position are independent of the wavelength. In the HLD the beam is fed into a circulare waveguide, guiding the radiation to the sample inside of a cryostat. To ensure the desired beam properties, the transport system has been analyzed by means of various ray and wave optical models.  
 
MOPPH073 Thermal and Non-thermal Laser Cutting Utilizing Advanced Industrial Lasers and ERL-FELs electron, free-electron-laser, linac, factory 175
 
  • E. J. Minehara
    JAEA/FEL, Ibaraki-ken
  The JAEA and JLAB energy-recovery free-electron lasers (ERL-FEL) have successfully demonstrated capabilities of a few hundreds fs ultra-fast pulse lasing, 6-9% high conversion efficiency, one GW high peak power, a few kW average power, and wide tunability of infrared wavelength regions. Utilizing the high average and high peak power lasing and energy-recovery linac (ERL) technology, we could realize a more powerful and more efficient FEL than 20kW and 25%, respectively, for nuclear industry, pharmacy, medical, defense, shipbuilding, semiconductor industry, chemical industries, environmental sciences, space-debris cleaning, power beaming and so on very near future. We have performed their thermal and non-thermal cutting and machining experiments and characterized their resultant effects. In order to compare some characteristic differences of thermal and non-thermal laser cutting utilizing advanced industrial laser like fiber, and water-guided ones and the ERL-FELs, we have performed some cutting trials of them. In the presentation, we plan to discuss these differences and how to apply all the lasers to the above applications in the fields.  
 
TUAAU05 Modelling Mirror Aberrations in FEL Oscillators Using OPC undulator, simulation, 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)

 
slides icon Slides  
 
TUBAU01 FLASH Upgraded - Preparing for the European XFEL electron, feedback, radiation, photon 211
 
  • H. Schlarb
    DESY, Hamburg
  Since 2005, the Free electron LASer in Hamburg, FLASH, has delivered a high brilliance photon beam to users in a wavelength range between 13 nm and 40 nm. To meet the user demands for 4 nm wavelengths, sub-50fs timing stability, and better pointing stability, the accelerator will be continuously upgraded within the next few years. The upgrade to an energy of 1.3 GeV, the transverse and longitudinal intra-train feedback system, and a 3rd harmonic cavity at 3.9 GHz are key prototype tests for the European XFEL. FLASH also serves as a test bench for an entirely new approach to accelerator facility synchronisation involving optical pulses distributed in length stabilized fibres. Increased stabilization of the electron beam peak current and its arrival time should provide the possibility to reliably seed the electron bunch with higher laser harmonics. In this paper, an overview of the planned upgrade for FLASH will be presented with respect to its usefulness for the European XFEL. The status of the XFEL project will also be briefly summarized.  
slides icon Slides  
 
TUBAU03 STARS – an FEL to Demonstrate Cascaded HGHG radiation, linac, emittance, electron 220
 
  • M. Abo-Bakr, W. Anders, J. Bahrdt, R. Follath, K. Goldammer, S. C. Hessler, K. Holldack, T. Kamps, B. C. Kuske, A. Meseck, T. Quast, J. Knobloch
    BESSY GmbH, Berlin
  BESSY plans to build the BESSY Soft X-ray FEL facility, a second generation FEL for the VUV and soft x-ray range. The TDR was evaluated by the German Science Council and recommended for funding subject to the condition that cascaded high-gain harmonic generation (HGHG) be demonstrated beforehand. To this end, BESSY is proposing the demonstration facility STARS for a two-stage HGHG FEL. For efficient lasing from 40 nm to 70 nm, a 325 MeV driver linac is required. It consists of a normal-conducting gun, superconducting TESLA-type modules modified for CW operation and a bunch compressor. The two-stage HGHG cascade employs variable gap undulators, with the final amplifier being an APPLE-III device for full polarization control. A beamline with user experiment completes STARS, which is planned to remain operational even after the BESSY FEL comes online. This paper summarizes the layout of STARS, the main parameters and the expected performance.  
 
TUPPH008 Beam Dynamics Studies on the UVSOR-II Free Electron Laser electron, injection, synchrotron, simulation 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.  
 
TUPPH012 Compact X-ray Free-Electron-Laser Based on an Optical Undulator undulator, radiation, electron, emittance 244
 
  • A. Bacci, C. Maroli, A. R. Rossi, L. Serafini
    INFN-Milano, Milano
  • V. Petrillo
    Universita' degli Studi di Milano, Milano
  • P. Tomassini
    INFN-Pisa, Pisa
  The interaction between a very high brightness electron beam and a relativistically intense optical laser pulse produces X rays via coherent Thomson back scattering with FEL collective amplification. The phenomenon is, however, very selective, so that the characteristics of both electron and laser beam must satisfy tight requirements in terms of beam current, emittance, energy spread and laser amplitude stability within the pulse. The three-dimensional equations governing the radiation phenomena have been studied in both linear and non linear regime and solved numerically for the particularly interesting values of wavelengths of 1 Ang, 1 nm and 12 nm. The performance of the collective Thomson source has been compared with that of an equivalent static undulator. A set of scaling laws ruling the phenomenon is also presented. The possibility of using an electron beam produced via LWFA in the bubble regime is investigated.  
 
TUPPH013 Production of Ultra-short Radiation Pulses in Frequency Doubler undulator, electron, radiation, simulation 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, radiation, simulation 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, simulation, 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, simulation, electron, 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.  
 
WEAAU01 Commissioning Results of the SLAC LCLS Gun cathode, gun, emittance, radiation 276
 
  • R. Akre, J. Castro, P. Emma, J. C. Frisch, A. Gilevich, G. R. Hays, P. Hering, R. H. Iverson, P. Krejcik, C. Limborg-Deprey, H. Loos, A. Miahnahri, J. F. Schmerge, J. L. Turner, J. J. Welch, W. E. White, J. Wu, D. Dowell
    SLAC, Menlo Park, California
  The beam quality and operational requirements for the Linac Coherent Light Source (LCLS) currently being constructed at SLAC are exceptional, requiring the design of a new s-band RF photocathode gun for the electron source. Two guns (Gun1 and Gun2) have been fabricated and tested at high RF power. Gun1 was installed March 17, 2007 and began providing beams for the LCLS injector commissioning on April 5, 2007. Gun2 is reserved as a backup gun. The results and analysis of the gun’s performance in the LCLS injector will be presented.  
slides icon Slides  
 
WEAAU02 Direct Measurement of Phase Space Evolution in the SPARC High Brightness Photoinjector emittance, simulation, 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.  
slides icon Slides  
 
WEAAU05 A Compact Electron Spectrometer for an LWFA electron, radiation, undulator, plasma 294
 
  • R. A. Crowell, K.-J. Kim, A. H. Lumpkin
    ANL, Argonne, Illinois
  The use of a laser wakefield accelerator (LWFA) beam as a driver for a compact Free-Electron Laser (FEL) has been proposed recently. A project is underway at Argonnne National Laboratory (ANL) to operate an LWFA in the bubble regime and to use the quasi-monoenergetic electron beam as a driver for a 3-m long undulator for generation of sub-ps UV radiation. The Terawatt Ultrafast High Field Facility (TUHFF) in the Chemistry division provides the 20 TW peak power laser. Towards this goal, a compact electron spectrometer whose initial fields of 0.45 T provide energy coverage of 30-200 MeV has been selected to characterize the electron beams. The system is based on the Ecole Polytechnique design* used for their LWFA and incorporates the 5-cm long permanent magnet dipole, the LANEX scintillator screen located at the dispersive plane, a Roper Scientific 16-bit MCP-intensified CCD camera, and a Bergoz ICT for complementary charge measurements. Test results on the magnets, the 16-bit camera, and the ICT will be described, and initial electron beam data will be presented as available.

*Y. Glinnec et al., "Broadrange Single Shot Electron Spectrometer", Report dated July 6, 2006, Ecole Polytechnique.

 
slides icon Slides  
 
WEBAU01 Adaptive 3-D UV-laser Pulse Shaping System to Minimize Emittance for Photocathode RF Gun emittance, electron, cathode, controls 298
 
  • T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T. Taniuchi, K. Yanagida, H. T. Tomizawa
    JASRI/SPring-8, Hyogo-ken
  • F. Matsui
    Industrial Technology Center of Fukui, Fukui City
  We developed an adaptive 3-D shaping (both temporal (1D) and spatial (2D)) short pulse (80 fs~40 ps) UV-laser system as an ideal light source for yearlong stable generation of a low emittance electron beam with a high charge (1~2 nC/pulse). In its current form, the laser’s pulse-energy stability has been improved to 0.2~0.3% (rms; 10 pps, 0.4 TW in femtosecond operation) at the fundamental wavelength and 0.7~1.4% at the third-harmonic generation. Such improvement reflects an ability to stabilize the laser system in a humidity-controlled clean room. The pulse-energy stability of a mode-locked femtosecond oscillator has been continuously held to 0.3% (p-p) for 10 months, 24 hours a day. In addition, the ideal spatial and temporal profiles of a shot-by-shot single UV-laser pulse are essential to suppress emittance growth in an RF gun. We apply a deformable mirror that automatically shapes the spatial UV-laser profile with a feedback routine, based on a genetic algorithm, and a pulse stacker for temporal shaping at the same time. The 3D shape of the laser pulse is spatially top-hat (flattop) and temporally a square stacked pulse. Using a 3D-shaped laser pulse with a diameter of 0.8 mm on the cathode and pulse duration of 10 ps (FWHM), we obtain a minimum normalized emittance of 1.4 π mm mrad with beam energy of 26 MeV.  
slides icon Slides  
 
WEBAU04 Single-Shot Longitudinal Bunch Profile Measurements at FLASH Using Electro-Optic Detection: Experiment, Simulation, and Validation electron, simulation, 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.  
slides icon Slides  
 
WEPPH005 Magnet Sorting for the European XFEL Hybrid Undulator - Comparing Study undulator, electron, controls, free-electron-laser 326
 
  • B. Faatz, J. Pflueger, Y. Li
    DESY, Hamburg
  Current permanent magnet material quality is insufficient to obtain field qualities in undulators, which satisfy FEL requirements. Therefore position and orientation of magnets have to be carefully chosen in order to obtain mutual cancellation of field errors. In this paper we compare two different sorting schemes, simulated annealing and a straight forward paring method. They are applied to a 5m prototype structure built for the European XFEL facility. The algorithms of these two methods are described in detail and the sorting results and the expected field qualities are carefully compared.  
 
WEPPH011 Photocathode Laser Pulse Diagnostics at PITZ cathode, diagnostics, electron, emittance 346
 
  • J. W. Baehr, S. A. Korepanov, M. Krasilnikov, F. Stephan, M. Hänel
    DESY Zeuthen, Zeuthen
  • Ye. Ivanisenko
    KhNU, Kharkov
  The main objective of the Photo Injector Test facility at DESY in Zeuthen (PITZ) is the development of electron sources that meet the requirements for existing and future FELs such as FLASH or the European XFEL. The goal is the minimization of the transverse emittance of the produced electron bunches. In this respect one of the key issues is the cathode laser system, which should provide longitudinal and transversal flat-top pulses with an excellent long-term stability. In this work we present the full system of laser diagnostics that is currently used at PITZ to monitor the laser pulse parameters.  
 
WEPPH012 Investigations on the Thermal Emittance of Cs2Te Photocathodes at PITZ emittance, cathode, electron, free-electron-laser 350
 
  • G. Asova, J. W. Baehr, C. H. Boulware, H.-J. Grabosch, M. Hänel, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, B. Petrosyan, S. Rimjaem, J. Roensch, T. A. Scholz, L. Staykov, F. Stephan, S. Lederer
    DESY Zeuthen, Zeuthen
  • K. Boyanov
    INRNE, Sofia
  • L. H. Hakobyan
    YerPhI, Yerevan
  • R. Richter
    BESSY GmbH, Berlin
  • A. Shapovalov
    MEPhI, Moscow
  The main objective of the Photo Injector Test facility at DESY in Zeuthen (PITZ) is the production of electron beams with minimal transverse emittance. The lower limit of this property of electron beams produced with a photocathode in an RF-gun is determined by the thermal emittance. To understand this crucial parameter for high performance FEL’s, measurements under RF operation conditions for Cesium Telluride (Cs2Te) photocathodes are done. Results for various accelerating gradients and the dependence on the laser spot size in the cathode plane are presented and discussed in this work.  
 
WEPPH014 Performance of the FERMI FEL Photoinjector Laser beam-transport, controls, monitoring, cathode 358
 
  • A. A. Demidovich, R. Ivanov, P. Sigalotti, M. B. Danailov
    ELETTRA, Basovizza, Trieste
  The photoinjector laser system for the FERMI FEL has been installed at the ELETTRA laser laboratory. It is based on a completely CW diode pumping technology and features a two stage pulse shaping system, a time-plate type third harmonic generation scheme and aspheric shaper based beam shaping. The paper will present experimental results describing the overall performance of the amplifier system as well as of the main sub-system listed above. The data demonstrates that all the initially set parameters were met and some largely exceeded. Special attention is dedicated to the pulse shaping allowing both flat-top and increasing ramp UV temporal shapes. A scheme for extraction and shaping of the laser heater pulses using the same laser system is also presented.  
 
WEPPH015 Modeling of a Laser Heater for Fermi@Elettra undulator, electron, linac, emittance 362
 
  • S. Di Mitri, S. Spampinati
    ELETTRA, Basovizza, Trieste
  To cure the microbunching instability in the FERMI@elettra FEL a laser heater is proposed. The one-dimensional model of the instability predicts a large energy modulation building up the electron beam travels through the linac. According to analytical studies and simulations the longitudinal Landau damping provided by the laser heater is expected to help in suppressing the formation of such a modulation. The efficiency of the beam heating is studied as function of the transverse laser-electron beam mismatch in the laser heater undulator in case of a realistic transverse beam profile.  
 
WEPPH017 UV Performances of Pulsed Laser Deposition Grown Mg Photocathodes cathode, vacuum, gun, electron 366
 
  • G. Gatti, F. Tazzioli, L. Cultrera
    INFN/LNF, Frascati (Roma)
  • P. Miglietta, A. Perrone
    INFN-Lecce, Lecce
  • C. Ristoscu
    INFLPR, Bucharest - Magurele
  We report a detailed description of the laser cleaning procedure and emission performance measurement on a Pulsed Laser Deposited Mg film. During the tests performed after the end of each cleaning operation we have evidenced an increase of Quantum Efficiency (QE) in time. Then the QE apparently stabilizes at a remarkably higher value. The study of this phenomenon is important because it determines both the working QE value and the lifetime of the cathode. Moreover, the stability of the QE has been revealed for a time scale of several days after each laser cleaning process, in our vacuum conditions.  
 
WEPPH021 Wide Band Seeding and Wavelength Compression electron, undulator, radiation, cathode 378
 
  • T. Shintake
    RIKEN Spring-8 Harima, Hyogo
  Seeding with optical laser and compressing wavelength in chicane bunch compressor has been studied theoretically. Overlapping laser beam with in comming electron beam in free space, with oblique crossing, we may apply energy modulation on relativisitic electron beam. When we use forth harmonic YAG-laser, 255 nm, and compressing 20 times, we have 13 nm density modulation period. Passing in undulator, which resonates to the compressed wavelength, the super-radiation mode beam will be generated. In contrast with SASE-FEL, this type of radiation source does not require high quality beam, ease to operate and coherent.  
 
WEPPH022 Feasibility Test of Shottoky Effect-Gated Photocathode RF Gun cathode, polarization, gun, focusing 382
 
  • M. Kobayashi
    Nanophoton corporation, Osaka
  • H. T. Tomizawa
    JASRI/SPring-8, Hyogo-ken
  We proposed Shottoky effect-gated photocathode RF gun using z-polarization of laser source. Radically polarized laser propagation modes exist theoretically and were recently generated practically. Focusing a radically polarized beam on the photocathode, the z-polarization of laser is generated at the focusing point. The generated Z-polarization can exceed an electrical field of 1GV/m easily with fundamental wavelength from compact femtosecond laser systems. According to our calculations, the z-field of 1GV/m needs 100MW at peak power for fundamental wavelength (790nm) and 25MW for SHG. In the field of 1GV/m, the work function of copper cathode reduces ~2 eV. The quantum efficiency will be ~10-4 at SHG by the Shottoky effect associated with the 1GV/m. This Shottky effect can be used as a gate of photo-emission process. In our design of Shottoky effect-gated Photocathode, the fundamental is used as gate pulse and SHG as laser source for photo-emission process. The same single laser pulse can also gate its emission by itself. To keep normal incidence on the cathode, we developed modified-Cessegrain-type incident optics combining with axicon lens pair. In the first test run, we are preparing z-polarizer for SHG to generate radial and azimuth polarizations. Comparing photo-emission process with these polarizations, we make clear the feasibility of this new concept of photocathode.  
 
WEPPH024 Numerical Evaluation of Oscillator FEL with Multi-Bunch Photo-Cathode RF-gun in Kyoto University electron, gun, undulator, emittance 390
 
  • Y. Kamiya, M. Washio
    RISE, Tokyo
  • T. Kii, K. Masuda, S. Sasaki, T. Shiiyama, H. Zen, H. Ohgaki
    Kyoto IAE, Kyoto
  • M. Kuriki, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • R. Kuroda
    AIST, Tsukuba, Ibaraki
  An infrared FEL (4-13 micro-m) facility to develop new energy materials is constructed in Institute of Advanced Energy, Kyoto University. The electron beam of 40 MeV has been successfully accelerated by a linac system which consists of a 4.5-cell thermionic RF gun*. However, due to severe back-bombardment effect, there still needs several efforts to extend the macro-pulse duration to obtain a stable FEL. Upgrade from the present thermionic RF gun to a photocathode RF gun has been planned in KU-FEL**, because a photocathode RF gun is free from the back-bombardment and can generate a high brightness electron beam. A multi-bunch photo-cathode RF gun system has been developed*** and will be installed into the KU-FEL linac. Thus a design work on the new linac system from the gun to the FEL has been performed by using PARMELA and GENESIS. The evaluated peak current is about 4 times and the expected FEL gain is about 10 times as high as those with the present system. The required laser system will be discussed in this conference, as well.

* H. Ohgaki, et al., NIM A, vol.528, pp.366-370 (2004).** H. Ohgaki, et al., Proc. of the FEL 2004, pp.454-457 (2004).*** K. Hirano, et al., NIM A, vol. 560, pp.233-239 (2006).

 
 
WEPPH030 Development of a Precise Timing System for the ISIR L-Band Linac at Osaka University linac, gun, electron, single-bunch 413
 
  • T. Igo, G. Isoyama, R. Kato, M. Morio, S. Suemine, S. Kashiwagi
    ISIR, Osaka
  We are developing a free electron laser (FEL) in the infrared region and also conducting SASE experiment in the same wavelength region using the L-band linear accelerator at the Institute of Scientific and Industrial Research (ISIR), Osaka University. In order to conduct such studies, stable operation of the linac is critical, so that we have developed a highly precise and flexible timing system for stable generation of the high intensity electron beam with the energy region of 10-30 MeV. In the timing system, a rubidium atomic clock producing 10 MHz rf signal is used as a time base for a synthesizer which is used as the master oscillator for generating the acceleration frequency of 1.3 GHz. The 1.3 GHz signal from the master oscillator is directly counted down to produce the clock signal of the timing system at 27 MHz and the four rf signals for the linac and laser used in the beam line. The start signal for the linac is precisely synchronized with the 27 MHz clock signal. To make an arbitrary delayed timing signal, a standard digital delay generator is used to make a gate signal for a GaAs rf switch, which slices out one of the 27 MHz clock pulses to generate the delayed timing signal. Any timing signal can be made at an interval of 37 ns and the timing jitter of the delayed signal is less than 2 ps (rms). We will report the new timing system and its performance in detail.  
 
WEPPH034 Fourier and Non-Fourier Models for Photoemission electron, vacuum, cathode, lattice 428
 
  • A. M. Mihalache, E. Mitru, M. Oane, C. Petit-Jean-Genaz
    INFLPR, Bucharest - Magurele
  This paper is a theoretical study on the photoemission properties of metallic photocathodes in the high intensity ultrashort laser pulse regime, using Fourier and non-Fourier models. First of all the Fourier-model was used. Next an analysis of the electron gas heating phenomenon and how this phenomenon leads to coupled heat equations (two temperature models). The authors also try to show that it is possible to use, in the second approximation, a non-Fourier model instead of two temperature models, using a single temperature hypothesis (the electron gas temperature equals with the lattice temperature). The distributions for thermal fields and photocurrents function of space, time, laser-intensity, incident angle and relaxation time are also represented.  
 
WEPPH038 Low Power Consuming Hybrid Bending Magnet at the XFEL Beam Dump electron, permanent-magnet, dipole, radiation 435
 
  • H. Danared, A. Hedqvist, F. Hellberg
    MSL, Stockholm
  • W. Decking, B. Krause, A. Petrov, J. Pflueger, M. Schmitz
    DESY, Hamburg
  At the end of the European XFEL the electron beam is separated from the photon beam and directed towards the beam dump with a bending magnet.* This dipole magnet is designed to bend 10-25 GeV electrons by 1 degree/m and is 10 meter long in total. By integrating permanent magnet material into a conventional electromagnet, this so called hybrid magnet with a 1 T bias magnetic field consumes no power at the nominal energy of the XFEL, 17.5 GeV. The magnetic field can be increased or decreased by magnet coils to obtain 1 degree/m deflection for all energies between 10 and 25 GeV. In case of component failures a passive safety system is needed to prevent the electron beam from reaching the experimental hall. The bias field of the permanent magnet not only saves power, but also works as a safety system for the XFEL. Here a proposal for such a hybrid configuration is presented together with its characteristics. The magnet is designed to use small amount of permanent magnet material and to consume less power than a conventional electromagnet.

*European XFEL Technical design report, edited by M. Altarelli et. al.,DESY 2006.

 
 
WEPPH039 The Optical Replica Synthesizer in FLASH undulator, electron, simulation, 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.  
 
WEPPH041 7th Harmonic Buncher Experiment at Neptune Laboratory undulator, electron, coupling, bunching 441
 
  • R. Tikhoplav, S. Tochitsky, P. Musumeci
    UCLA, Los Angeles, California
  Since typically FEL undulator magnets have period length in the cm range, and the normalized magnetic field strength K is maintained close to unity to guarantee a good coupling, a very high energy electron beam is needed to access the far UV and x-ray region of the electromagnetic spectrum. One way to reduce the beam energy necessary for short wavelength light sources consists of exploiting the FEL harmonic interaction. An experiment aimed at demonstrating the efficiency of harmonically coupled schemes is proposed for the Neptune Laboratory at UCLA. We plan to inject the 12.4 MeV beam from the split photoinjector in an already available undulator with period = 3.3 cm and K = 1.8. The FEL resonant wavelength with these parameters is 74.2 um. A copropagating high power 10.6 um CO2 laser bunches the beam via 7th harmonic FEL/IFEL interaction. Preliminary calculations show that even though the interaction is weakened by the high harmonic number, it is required to use only 5 -10 MW of power in order to induce full bunching on the beam in the 10 period long undulator.  
 
WEPPH043 The UCSB MM-FEL Injection Locking System injection, free-electron-laser, electron, coupling 445
 
  • S. Takahashi, G. J. Ramian
    UCSB, Santa Barbara, California
  An Injection locking system has been implemented on UCSB's Millimeter Wave FEL at 240 GHz. It it is based on a VDI varactor multiplier source and a Keating quasi-optical isolator. Its purpose is to stabilize lasing and suppress mode beating by always forcing lasing to occur at a single frequency on one specific longitudinal mode. Theoretical and experimental results are presented.  
 
WEPPH046 A Superconducting RF Photo-Injector for Operation at the ELBE Linear Accelerator gun, cathode, vacuum, electron 449
 
  • A. Arnold, H. Buettig, D. Janssen, M. Justus, U. Lehnert, P. Michel, K. Moeller, P. Murcek, Ch. Schneider, R. Schurig, F. Staufenbiel, R. Xiang, J. Teichert
    FZD, Dresden
  • T. Kamps
    BESSY GmbH, Berlin
  • G. Klemz, I. Will
    MBI, Berlin
  • W.-D. Lehmann
    IfE, Dresden
  • A. Matheisen, B. van der Horst
    DESY, Hamburg
  • J. Stephan
    IKST, Drsden
  • V. Volkov
    BINP SB RAS, Novosibirsk
  • P. vom Stein
    ACCEL, Bergisch Gladbach
  For the ELBE superconducting linear accelerator at Forschungszentrum Dresden-Rossendorf (FZD) a radiofrequency photoelectron injector with a superconducting cavity (SRF gun) is under development. The SRF gun combines the excellent beam quality which can be delivered by RF photoinjectors with the possibility of continuous wave operation. The superconducting niobium cavity of the injector consists of 3½ cells and contains a Cs2Te photocathode which is normal-conducting and cooled by liquid nitrogen. The RF frequency of the cavity is 1.3 GHz. The final electron energy will be about 9.5 MeV and the average electron current will be 1 mA. In the past years the SRF photo injector has been designed and fabricated. Several critical subsystems have been tested. For the cavity, the results of the RF measurements will be shown. An UV driver laser system has been developed which fulfils the different requirements (77 pC at 13 MHz, 1 nC at 500 kHz) for the future operation at ELBE. A photo cathode preparation system was developed and installed. The equipment is now in operation and the first series of Cs2Te photo cathodes have been produced.  
 
WEPPH047 Electro-Optic Spectral Decoding for Single-Shot Characterisation of the Coherent Transition Radiation Time Structure at FLASH radiation, vacuum, electron, background 453
 
  • E.-A. Knabbe, B. Schmidt, P. Schmüser, B. Steffen, V. R. Arsov
    DESY, Hamburg
  Characterisation of the longitudinal profiles of ultrashort electron bunches is of primary importance for controlling the lasing process of SASE FEL. Non-destructive, single-shot techniques, are preferable. Presently the most promising ones are the Electro-Оptic (EO) laser diagnostics and the THz spectroscopy of coherent transition radiation (CTR). Whereas the former are applied directly in the electron beam line, the latter offer possibility to detect shorter temporal structures, but outside the tunnel. Therefore it is important to know the transfer function of the CTR beam line. We present a single-shot EO detection of temporal CTR profiles, generated from electron bunches, kicked to an off-axis screen at DESY's VUV-FEL (FLASH). The THz radiation is transported through a 20 m long line from the accelerator tunnel to an experimental station outside. The measurements are performed in air and in vacuum with 0.5 mm ZnTe and 0.175 mm GaP crystals in crossed-polarisers detection scheme. Pulses with less than 1 ps FWHM have been measured.  
 
WEPPH048 XPS Studies of Cs2Te Photocathodes cathode, electron, photon, survey 457
 
  • H. A. Duerr, R. Ovsyannikov, M. Sperling, A. Vollmer
    BESSY GmbH, Berlin
  • J. H. Han, S. Schreiber, S. Lederer
    DESY, Hamburg
  • P. Michelato, L. Monaco, C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI)
  • F. Stephan
    DESY Zeuthen, Zeuthen
  Cesium Telluride (Cs2Te) photocathodes are used as sources for electron beams because of their high quantum efficiency (QE) and their ability to release high peak current electron bunches in a high gradient RF-gun. Starting from a high QE level of about 10% the quantum efficiency of these cathodes decreases during operation in a photo-injector to below 0.5%. To understand this behaviour, XPS investigations on the chemical composition were performed at BESSY. In this contribution we compare two fresh cathodes from INFN with one used under normal operation at FLASH and one used at PITZ at a higher than usual RF-gradient of 60 MV/m.  
 
WEPPH052 In-situ Undulator Field Measurement with the SAFALI System undulator, feedback, vacuum, electron 468
 
  • H. Kitamura, T. Tanaka
    RIKEN Spring-8 Harima, Hyogo
  • T. Seike
    JASRI/SPring-8, Hyogo-ken
  Although the in-vacuum undulators (IVUs) have many advantages over out-vacuum undulators, magnetic measurement after assembling vacuum components, i.e., final verification of magnetic performance, is not an easy task. In addition, remeasurement after installation in the accelerator beamline is not trivial. The situation is more severe for cryogenic permanent magnet undulators (CPMUs), an extension of IVUs. We have recently developed a magnetic measurement system to measure the field inside the vacuum chamber. With optical laser beams introduced into the vacuum chamber, the alignment of the Hall probe positions is dynamically carried out, which ensures a high stability and accuracy of the measurement. This system is called SAFALI for Self-Aligned Field Analyzer with Laser Instrumentation. The SAFALI system has been applied to field measurement of two different undulators. One is an IVU installed in Swiss Light Source in 2001 and had been operated for about 3 years. The other is a CPMU prototype to demonstrate the principle of CPMU. The purpose of the measurement of the former is to investigate the radiation damage during operation, while that of the latter is to check the performance variation according to the temperature change of magnets. In the conference, details of the SAFALI system are given together with the results of the field measurements.  
 
WEPPH053 Non-Destructive Single-Shot 3-D Electron Bunch Monitor with Femtosecond-Timing All-Optical System for Pump & Probe Experiments electron, multipole, optics, polarization 472
 
  • H. Hanaki, H. T. Tomizawa
    JASRI/SPring-8, Hyogo-ken
  • T. Ishikawa
    RIKEN Spring-8 Harima, Hyogo
  We are developing a 3-D electron bunch monitor based on EO sampling, using yearlong stable femtosecond laser source of SPring-8 RF gun. Our developing single-shot bunch monitor can characterize the 3-D (both longitudinal (1D) and transverse (2D)) distribution and position of an electron bunch with femtosecond resolution. This non-destructive monitor can be used as an electron energy chirping monitor in a dispersive region for X-FEL commissioning. The probe laser for spectral decoding EO sampling is prepared as radically polarized and completely linearly chirped broad-bandwidth (~500nm) supercontinuum. EO-probe is made of 8 EO-crystals with assembling each EO-optical axes along radial beam axes. The probe lineally chirped laser is longitudinally sifted in 8 transverse sectors for spectral decoding. We are planning to use organic polymer film as a femtosecond resolution EO-probe instead of crystals. This 3-D bunch monitor with spectrograph detects and analyzes the wake filed of electron bunches as longitudinally spectral decoding and transversely multi-pole expansion. In addition, we are developing all-optical system for femtosecond-timing pump & probe experiments. The EO-sampled probe laser pulse will use as a femtosecond-timing signal pulse. This signal pulse is amplified with a NOPA (noncollinear optical parametric amplifier), using an SHG of Yb fiber laser as a pump laser.  
 
THAAU01 Experience and Plans of the JLAB FEL Facility as a User Facility free-electron-laser, electron, radiation, linac 491
 
  • M. D. Shinn
    Jefferson Lab, Newport News, Virginia
  Jefferson Lab’s IR Upgrade FEL building was planned from the beginning to be a user facility, and includes an associated 600 sq. m area containing seven laboratories. The high average power capability (multikilowatt-level) in the near-infrared (1-3 microns), and many hundreds of watts at longer wavelengths, along with an ultrafast (~ 1 ps) high PRF (10’s MHz) temporal structure makes this laser a unique source for both applied and basic research. In addition to the FEL, we have a dedicated laboratory capable of delivering high power (many tens of watts) of broadband THz light. After commissioning the IR Upgrade, we once again began delivering beam to users in 2005. In this presentation, I will give an overview of the FEL facility and its current performance, lessons learned over the last two years, and a synopsis of current and future experiments.  
slides icon Slides  
 
THAAU03 Experimental Study of Volume Free Electron Laser Using a "Grid" Photonic Crystal with Variable Period electron, radiation, free-electron-laser, feedback 496
 
  • V. G. Baryshevsky, N. A. Belous, V. A. Evdokimov, A. Gurinovich, A. S. Lobko, A. V. Oskin, P. F. Safronov, P. V. Molchanov
    Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk
  Electrodynamical properties of a crystal-like artificial periodic structure (photonic crystal) formed by a periodically strained metallic threads were studied both theoretically and experimentally*,**. In the present paper operation of Volume Free Electron Laser using a "grid" photonic crystal with variable period is experimentally studied. Dependence of the generation threshold on photonic crystal length is investigated along with the frequency characteristics of generated radiation.

* Baryshevsky V. G. et al. NIM section B. Vol252 (2006) P.92-101 ** Baryshevsky V. G. et al. Proc. of the 28th FEL Conference PP.331-338

 
slides icon Slides  
 
THBAU01 Research Highlights from FLASH free-electron-laser, electron, radiation, vacuum 499
 
  • J. Feldhaus, R. Treusch
    DESY, Hamburg
  The Free electron LASer in Hamburg (FLASH) has started regular user operation in summer 2005, providing XUV radiation pulses with pulse energies in the 10 - 100 μJ range and pulse durations of 10 - 50 fs. The science programme at FLASH covers a broad range of novel applications including fundamental studies on atoms, ions, molecules and clusters, creation and characterisation of warm dense matter, diffraction imaging of nanoparticles, spectroscopy of bulk solids and surfaces, investigation of surface reactions and spin dynamics, and the development of advanced photon diagnostics and experimental techniques. So far, 16 science projects have been pursued involving approximately 200 scientists from 11 countries. Some of the research highlights will be presented.  
slides icon Slides  
 
FRAAU01 Source of Radiation on ARC-EN-CIEL Proposal undulator, radiation, electron, cryogenics 505
 
  • O. V. Chubar, M. Labat, G. Lambert, O. Marcouillé, M.-E. Couprie
    SOLEIL, Gif-sur-Yvette
  The ARC-EN-CIEL project proposes a panoply of light sources for the scientific community. The phase 1 (220 MeV superconducting Linac, down to 30 nm) and phase 2 (1 GeV, down to 1 nm) choice to provide 30-100 fs HGHG radiation and their Non Linear Harmonics seeded with the High order Harmonics generated in Gas is further confirmed with the suceesfull demonstration experiment of such a scheme at SPA. New optimizations of the undulatros lead to in vacuum undulators of period 26 mm for the modulator, and APPLE-type radiators of period 30 mm, close to the standard SOLEIL insertion devices. New calculations have been carried out using PERSEO TD and GENESIS coupled to SRW for further propagation of the FEL wavefront to the beamlines. In addition, THz radiation from the magnets of the compression chicanes will be provided and has been calculated using SRW. ARC-EN-CIEL Phase 3 incorporates ERL loops, for hard X ray spontaneous emission above 10 keV from short period in vacuum undulators (20 mm period typically), one Soft-X ray spontaneous emission beamline using an variable polarisation undulator, and an FEL oscillator in the 10-60 nm spectral range. Recent calculations and optimisations will be presented.  
slides icon Slides  
 
FRAAU02 Status of the FEL Test Facility at MAX-lab gun, electron, linac, emittance 513
 
  • M. Abo-Bakr, J. Bahrdt, K. Goldammer
    BESSY GmbH, Berlin
  • M. Brandin, F. Lindau, D. Pugachov, S. Thorin, S. Werin
    MAX-lab, Lund
  • A. L'Huillier
    Lund University, Division of Atomic Physics, Lund
  An FEL test facility is built on the existing MAX-lab linac system in collaboration between MAX-lab and BESSY. The goal is to study and analyse seeding, harmonic generation, beam compression and diagnostic techniques with the focus of gaining knowledge and experience for the MAX IV FEL and the BESSY FEL projects. The test facility will in the first stage be using the 400 MeV linac beam to generate the third harmonic at 90 nm from a 266 nm Ti:SA seed laser. The optical klystron is installed and magnetic system, gun and seed laser systems are currently being finalised. Start-to-end simulations have been performed and operation modes for bunch compression defined. The linac and beam transport system is already in operation. We report the status and layout of the project, the issues to be addressed, the solutions for bunch compression and operation. We also report on the prospects of extending the seeding to HHG laser systems.  
slides icon Slides