FEL 2007 - List of Keywords (electron)

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

electron

Paper	Title	Other Keywords	Page
MOBAU01	Self-Force-Derived Mass of an Electron Bunch	acceleration, electromagnetic-fields, synchrotron, synchrotron-radiation	1
	E. Saldin DESY, Hamburg
	The properties of Lorentz transformations for energy and momentum in electromagnetic systems are illustrated in a simple example involving a short electron bunch moving in a bending magnet. The famous 4/3 problem in electromagnetic mass is discussed.
	Slides

MOBAU02	Technology Challenges Towards Short-Wavelength FELs	emittance, undulator, radiation, space-charge	9
	J. Rossbach Uni HH, Hamburg
	Since the very first proposal of high-gain FELs for the X-ray wavelength regime it was obvious that realization of such a device, potentially rewarding revolutionary science opportunities, would impose extraordinary challenges in terms of accelerator physics and technology. The talk will review the major steps that had to be taken to finally construct an FEL user facility for soft X-rays. Also, a few issues will be pointed out that are to be addressed in order to make full profit of the FEL principle at X-ray wavelengts.
	Slides

MOPPH003	VOLC: Volume Free Electron Laser Simulation Code	simulation, 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.

MOPPH006	Longitudinal Wake Field for an Electron Beam Accelerated through a Ultra-High Field Gradient	impedance, acceleration, undulator, radiation	26
	E. Saldin, E. Schneidmiller, M. V. Yurkov, G. Geloni DESY, Hamburg
	Electron accelerators with higher longitudinal field gradients can produce high-energy beams with compact, cheap setups. Laser-plasma acceleration appears to constitute the more promising breakthrough in this direction, delivering field gradients up to TV/m. Here we describe the impact of longitudinal wake fields on the electron beam, based on solution of Maxwell's equations for the longitudinal field. We consider an acceleration distance much smaller than the overtaking length (the length that electrons travel as a light signal from the tail of the bunch overtakes the head of the bunch), that is the case for laser-plasma devices. We give expressions for impedance and wake function that may be evaluated numerically. We show that the rate of energy loss in the bunch due to radiative interaction is equal to that of coherently radiated energy in the far-zone. A limiting expression is found for a large distance of the electron beam from the accelerator compared with the overtaking length. We derive analytical solutions for a Gaussian transverse and longitudinal bunch shape. We apply our analytical asymptote by studying the feasibility of a Table-Top FEL based on laser-plasma driver. Numerical estimations indicate that the effects of the time-dependent energy change induced by the longitudinal wake pose a serious threat to the operation of this device. (See DESY 06-222)

MOPPH007	Theory of Nonlinear Harmonic Generation in Free-Electron Lasers with Helical Wigglers	undulator, wiggler, radiation, resonance	30
	E. Saldin, E. Schneidmiller, M. V. Yurkov, G. Geloni DESY, Hamburg
	Coherent Harmonic Generation (CHG), and in particular Nonlinear Harmonic Generation (NHG), is of importance for both short wavelength Free-Electron Lasers (FELs), in relation with the achievement of shorter wavelengths with a fixed electron-beam energy, and high-average power FEL resonators, in relation with destructive effects of higher harmonics radiation on mirrors. In this paper we present a treatment of NHG from helical wigglers with particular emphasis on the second harmonic. Our study is based on an exact analytical solution of Maxwell's equations, derived with the help of a Green's function method. In particular, we demonstrate that nonlinear harmonic generation (NHG) from helical wigglers vanishes on axis. Our conclusion is in open contrast with results in literature, that include a kinematical mistake in the description of the electron motion. (See DESY 07-058)

MOPPH010	Three-Dimensional Analysis of the Surface Mode Supported by a Reflection Grating	electromagnetic-fields, laser, 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.

MOPPH011	Comparison Between Kinetic and Fluid Description of Plasma-Loladed Free-Electron Laser	plasma, radiation, wiggler, space-charge	42
	S. Babaei, B. Maraghechi AUT, Tehran
	In the kinetic treatment of the plasma-loaded FEL in Ref.* single particle equation of motion, for both beam and plasma electrons in the radiation fields, are used. Therefore, interaction terms between the wiggler and the space-charge wave, in the transverse velocity of electrons, which are important elements in the fluid model, are neglected. A dispersion relation of a plasma-loaded FEL with kinetic theory is found in Ref.* that takes into account the velocity spread of both beam and plasma electrons. In the present analysis, a dispersion relation is obtained, by the fluid theory, with the interaction terms between the wiggler and the space-charge wave in the transverse velocity of electrons taken into account. Since these interaction terms are inherently missing in the kinetic theory the two dispersion relation are compared to find out about the importance of these terms. It was found that although the absence of these terms has considerable effects on the growth rate, the general kinetic dispersion relation may be used to study the temperature effects of a warm beam/plasma on the instability of a free-electron laser with a plasma background. * S. Babaei and B. Maraghechi, "Kinetic description of plasma-loaded free-electron laser", Phys. Plasmas, to be published.

MOPPH012	Conservation Laws in Quasilinear Theory of Raman Free-Electron Laser	space-charge, plasma, free-electron-laser, 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, radiation, laser, 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, undulator, free-electron-laser, 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, laser	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.

MOPPH020	FEL with Orotron Type Feedback	coupling, radiation, feedback, undulator	61
	R. Ando, K. Kamada Kanazawa University, Kanazawa N. S. Ginzburg, N. Yu. Peskov, R. M. Rozental, A. Sergeev, V. Yu. Zaslavsky, A. Malkin IAP/RAS, Nizhny Novgorod
	In microwave electronics orotron is widely used as a source of RF radiation in millimeter and submillimeter wavebands. In this device an electron beam is coupled to a mode of quasi-optical resonator by means of the periodical grating one of the resonator mirror. In our paper we discuss a relativistic modification of such a device. A novel FEL scheme is suggested in which the slow wave structure of orotron is replaced by shallow Bragg corrugation which provides the coupling of the transverse (with respect to direction of beam propagation) mode of a two-mirror cavity with longitudinally propagating wave. The latter can be excited by the electron beam wiggling in undulator field. Described scheme allows to combine selective properties of an orotron with relativistic frequency conversion of a free electron laser. The transverse mode provides the feedback in the system thus leading to self-excitation, while the propagating wave is responsible for energy extraction in the steady-state regime of operation. The discussed system was investigated both analytically and numerically using direct codes and averaged equations approach.

MOPPH022	A Description of Guided FEL Radiation Using Dielectric Waveguide Eigenmodes	radiation, undulator, coupling, bunching	65
	A. Gover University of Tel-Aviv, Faculty of Engineering, Tel-Aviv J. B. Rosenzweig, E. Hemsing UCLA, Los Angeles, California
	An analysis of the radiation field of an FEL in terms of eigenmodes of a linear dielectric waveguide is presented.

MOPPH023	Enhancing FEL Power with Phase Shifters	undulator, radiation, simulation, 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.

MOPPH025	Three-dimensional Theory of the Cerenkov Free-Electron Laser	laser, 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	laser, 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.

MOPPH030	Terahertz Imaging and Radioscopy with 160x120 Microbolometer 90 fps Camera	radiation, free-electron-laser, laser, 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, laser, diagnostics	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.

MOPPH033	Diffraction Optical Elements and Optical Systems with a High Power Monochromatic Terahertz Source	radiation, focusing, free-electron-laser, laser	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, laser, 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	laser, 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	laser, 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	laser, 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, laser, 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).

MOPPH046	Operation of Near-infrared FEL at Nihon University	coupling, linac, undulator, klystron	114
	A. Enomoto, S. Fukuda, K. Furukawa, S. Michizono, S. Ohsawa KEK, Ibaraki Y. Hayakawa, K. Nakao, K. Nogami, T. Tanaka, K. Hayakawa LEBRA, Funabashi M. Inagaki, T. Kuwada, T. Sakai, I. Sato Nihon University
	The near-infrared FEL at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been operated for a variety of scientific applications since 2003. The stability of the FEL power was improved appreciably by the advanced stability of the 125 MeV electron linac. Currently fundamental FEL wavelength ranges from 1 to 6 microns, which is restricted by the electron energy and the optical devices. The higher harmonics in the visible region is also available. The maximum macropulse output energy of 60 mJ/pulse has been obtained at a wavelength of 1725 nm. The short FEL resonator at LEBRA causes relatively high optical energy density on the surface of the resonator mirrors; present copper-based Ag mirrors in use at LEBRA are not durable enough for long term operation. As an alternative way of generating intense harmonics in the visible to near-UV region, second and third harmonic generation by means of non-linear optical devices has been tested for the FELs around 1.5 microns as input fundamental photons.

MOPPH048	ARC-EN-CIEL Project Electron Beam Dynamics	emittance, linac, focusing, quadrupole	118
	M.-E. Couprie, A. Loulergue, C. Bruni SOLEIL, Gif-sur-Yvette
	ARC-EN-CIEL project is based on the development of fourth generation light source of high brilliance and tunable in the UV-X domain. The project will evolved into three phases leading to different light performances: first and second phases are in single pass configuration with energy of 220 MeV and 1 GeV respectively, while third phase comports recirculation loops at 1 GeV and 2 GeV. For delivering a high brilliance light source with high peak power short pulses, the high charge electron beam should have subpicoseconde duration with low emittance and energy spread. In order to keep optimal slice characteristics for light production, phase space non linearities due to optics aberrations and collective effects should be minimized. In ERL configuration, a critical consequence of collective effects is the Beam Break Up instability, which forms a feedback loop between the beam and the cavities. This contribution aims at presenting the electron beam dynamics for the ARC-EN-CIEL project in single pass and ERL configuration, especially on the conditions for minimizing non linearities and Beam Break Up instability.

MOPPH050	Status of the Undulator System of the Seeded HGHG-FEL Test Bench at MAX-lab	radiation, undulator, simulation, 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, simulation, 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.

MOPPH052	Output Performance of the STARS HGHG Demonstrator at BESSY	undulator, radiation, emittance, laser	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.

MOPPH054	Small-Aperture Vacuum-Chamber Design for STARS	vacuum, undulator, scattering, radiation	134
	J. Bahrdt, V. Duerr, M. Scheer, G. Wuestefeld, A. Meseck BESSY GmbH, Berlin
	To demonstrate and investigate the cascaded HGHG-scheme proposed for the BESSY Soft X-ray FEL, BESSY plans to build a test-facility called STARS consisting of two HGHG stages. The radiator in the second stage is planned as an APPLE III device which provides the highest field for a circular beam pipe. The minimum Gap of 7 mm translates into a 5 mm inner diameter of the vacuum chamber. An analysis of the impact of the wakefields and the expected vacuum profile is thus required. Results of this analysis an vacuum measurements are presented.

MOPPH060	The Drive Laser System for CFEL	laser, feedback, 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.

MOPPH061	Design of the PAL Test FEL Machine	linac, undulator, emittance, simulation	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.

MOPPH062	Features of the PAL-XFEL Design	undulator, radiation, emittance, brightness	152
	J. Choi, H.-S. Kang, T.-Y. Lee PAL, Pohang, Kyungbuk
	The PAL-XFEL design has been revised since the previous conference. The 2nd bunch compressor has been moved to a higher energy to eliminate the space charge effect and the total linac energy has been increased from 3.7 GeV to 4.0 GeV. Details and reasons of these design revisions are explained in this paper.

MOPPH063	Potentialities of ELMI Device for Submillimeter Generation by Stimulated Intercavity Scattering in Planar FEM	radiation, scattering, simulation, 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.

MOPPH064	A Project of SC ERL at KAERI	sextupole, emittance, undulator, dipole	160
	Y. H. Han, Y. U. Jeong, B. C. Lee, S. H. Park KAERI, Daejon S. V. Miginsky, A. V. Bondarenko BINP SB RAS, Novosibirsk
	A project of an ERL at Korea Atomic Energy Research Institute is described. The ERL will be connected to the existing machine without any modification. It consists of two 180° bents and two straight sections: one is for an FEL, another for a Compton X-ray source. One can choose the regime controlling the lenses. The total ERL is isochronous to avoid any problem with longitudinal beam instability. It will be possible to control both Sx and Sy transormation matrix elements independently to suppress longitudinal beam instability and allow the increase of beam current. Sextuples will be installed in bents to suppress chromatic aberration. This design provides operation in FEL regime with high electron efficiency in the range of electron energies 12–22 MeV.

MOPPH068	The NCAS-FEL: an FEL Oscillator with High Slippage	undulator, radiation, simulation, 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	simulation, radiation, 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.

MOPPH072	The IR-Beam Transport System from the ELBE-FELs to the User Labs	diagnostics, laser, 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	laser, 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.

MOPPH074	Preliminary Design of the Proposed IR-FEL in India	simulation, 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, simulation, 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.
	Slides

MOCAU02	Numerical Solution of the FEL Correlation Function Equation	undulator, radiation, simulation	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
	Slides

MOCAU04	Impact of Longitudinal Space-charge Wake from FEL Undulators on Current-enhanced SASE Schemes	impedance, undulator, space-charge, radiation	196
	E. Saldin, E. Schneidmiller, M. V. Yurkov, G. Geloni DESY, Hamburg
	In this article we present a description of longitudinal wake fields in X-ray Free-Electron Lasers (XFELs) that is of relevance in relation with Enhanced Self-Amplified Spontaneous Emission (ESASE) schemes. We consider wakes in XFELs, in the limit when the electron beam has gone inside the undulator for a distance longer than the overtaking length (the length that electrons travel as a light signal from the tail of the bunch overtakes the head of the bunch). We find that the magnitude of the resulting energy chirp constitutes a reason of concern for the practical realization of ESASE schemes.
	Slides

MOCAU05	Space Charge Effect in an Accelerated Beam	acceleration, space-charge, radiation, electromagnetic-fields	200
	Z. Huang, G. V. Stupakov SLAC, Menlo Park, California
	It is usually assumed that the space charge effects in relativistic beams scale with the energy of the beam as the inverse relativistic factor gamma factor squared. We show that for a beam accelerated in the longitudinal direction there is an additional space charge effect in free space that scales as the ratio of the accelerating field to the gamma factor. This space charge field has the same origin as the "electromagnetic mass of the electron" discussed in textbooks on electrodynamics. It keeps the balance between the kinetic energy of the beam and the energy of the electromagnetic field of the beam. We then consider the effect of this field on a beam generated in an RF gun and calculate the energy spread produced by this field in the beam.
	Slides

TUAAU02	Electron Outcoupling Scheme for the Novosibirsk FEL	undulator, radiation, bunching, simulation	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
	Slides

TUBAU01	FLASH Upgraded - Preparing for the European XFEL	laser, 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

TUBAU02	Status of SCSS & X-ray FEL Project in Japan	emittance, gun, undulator, cathode	216
	T. Shintake RIKEN Spring-8 Harima, Hyogo
	Staus of SCSS project after the first lasing last year will be reported. The X-ray FEL, which uses 8 GeV C-band, is under construction, whose status will be reported.
	Slides

TUBAU03	STARS – an FEL to Demonstrate Cascaded HGHG	radiation, linac, emittance, laser	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.

TUBAU04	Towards a Low Emittance X-ray FEL at PSI	emittance, acceleration, cathode, simulation	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.
	Slides

TUPPH006	FEL Potential of the High Current ERLs at BNL	emittance, linac, gun, simulation	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, 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.

TUPPH011	Analytical Studies of Transverse Coherence Properties of X-ray FELs	radiation, undulator, emittance, free-electron-laser	240
	E. Schneidmiller, M. V. Yurkov, E. Saldin DESY, Hamburg
	We describe analytically the process of formation of transverse coherence in X-ray SASE FELs.

TUPPH012	Compact X-ray Free-Electron-Laser Based on an Optical Undulator	laser, undulator, radiation, 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, radiation, laser, 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, laser, 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.

TUPPH015	Diffraction Effects in the Coherent Transition Radiation Bunch Length Diagnostics	radiation, diagnostics, injection, photon	256
	V. A. Lebedev, S. Nagaitsev, G. M. Kazakevich Fermilab, Batavia, Illinois
	Diffraction effects in the Coherent Transition Radiation (CTR) bunch length diagnostics were considered for the A0 Photoinjector and the ILC injection module. The effects can cause a noticeable distortion of the measured CTR spectra dependently on the experimental setup and the bunch parameters. The distortion results in the the errors of the bunch length determination. Presented calculations show possible errors in determination of the bunch length in assumed experiments based on the CTR spectra measurements at A0 Photo injector and the ILC injection module.

TUPPH020	Quiet Start Method in small signal HGHG FEL Simulation	bunching, simulation, 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.

TUCAU01	FELs and High-energy Electron Cooling	hadron, collider, proton, plasma	268
	Y. S. Derbenev Jefferson Lab, Newport News, Virginia V. Litvinenko BNL, Upton, Long Island, New York
	Electron cooling is extremely successful in cooling low and medium energy ions, including protons. ERLs are promising to extend the reach of traditional electron cooling to about 100 GeV/nucleon for heavy ions. Nevertheless, cooling of protons with energies from about 100 GeV (RHIC) to few TeV (LHC) becoming very complicated or even possible. Optical stochastic cooling [1] has potential to be an instrument of choice, but it has two main shortcomings: a) it requires significant modifications of the lattices of hadron machine and b) in the case of the protons it suffers from very inefficient interaction (radiation) of protons with TEM wave. It was suggested [2] to combine advantages of electrostatic interaction with broad-band FEL-amplifier in what is now called stochastic electron cooling. Such system will naturally fit into a straight section of modern high energy hadron colliders. In this paper we present description of the cooling process and give examples of FEL-based electron cooler for protons in RHIC and LHC. [1] A. Mikhalichenko and M. Zolotorev, Phys. Rev. Lett., 71, p.4146 (1993). [2] Ya. S. Derbenev, NIM A441 (2000) 223
	Slides

WEAAU04	Superconducting Photoinjector for High-Power Free Electron Lasers	gun, cathode, emittance, linac	290
	A. Burrill, R. Calaga, X. Chang, R. Grover, R. C. Gupta, H. Hahn, L. Hammons, D. Kayran, J. Kewisch, R. F. Lambiase, V. Litvinenko, G. T. McIntyre, D. Naik, D. Pate, D. Phillips, E. Pozdeyev, T. Rao, J. Smedley, R. J. Todd, D. Weiss, Q. Wu, A. Zaltsman, I. Ben-Zvi BNL, Upton, Long Island, New York M. D. Cole, M. Falletta, D. Holmes, J. Rathke, T. Schultheiss, A. M.M. Todd, R. Wong AES, Medford, NY
	One of the frontiers in FEL science is that of high power. In order to reach power in the megawatt range, one requires a current of the order of one ampere with a reasonably good emittance. The superconducting laser-photocathode RF gun with a high quantum efficiency photocathode is the most natural candidate to provide this performance. The development of a 1/2 cell superconducting photoinjector designed to operate at a current of 0.5 amperes and beam energy of 2 MeV and its photocathode system are the subjects covered in this paper. The main issues are the photocathode and its insertion mechanism, the power coupling and High Order Mode damping. This technology is being developed at BNL for DOE nuclear physics applications such as electron cooling at high energy and electron ion colliders.
	Slides

WEAAU05	A Compact Electron Spectrometer for an LWFA	laser, 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

WEBAU01	Adaptive 3-D UV-laser Pulse Shaping System to Minimize Emittance for Photocathode RF Gun	laser, emittance, 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

WEBAU03	Performance Tests of the Photon Monochromator for Self-seeding at FLASH	photon, undulator, radiation, vacuum	306
	H. K. Bechtold, J. Hartvig, H. Juul, V. Toft Aarhus University, Aarhus R. Follath, G. Reichardt, F. Senf, F. Siewert BESSY GmbH, Berlin U. Hahn, J. Viefhaus, R. Treusch DESY, Hamburg S. V. Hoffmann ISA, Aarhus Ch. Knoechel LBNL, Berkeley, California R. Reininger UW-Madison/SRC, Madison, Wisconsin
	A single pass FEL amplifier can produce extremely intense and fully coherent radiation at short wavelengths if it is seeded by a coherent light beam resonant with the magnetic structure and collinear with the electron beam. Since at the present time a single pass SASE FEL is the only source of sufficiently intense, tunable radiation in the soft X-ray region, it has been proposed to use such a source in combination with a narrow-band monochromator for seeding an FEL amplifier. By means of such a "Self-Seeding", the soft X-ray free electron laser FLASH at DESY will be modified so that it can provide coherent radiation in space and time in a wavelength range from about 60-6nm (~20-200eV). In this presentation, we will focus on the performance of the photon monochromator beamline which was setup and tested at the synchrotron radiation storage ring ASTRID in Aarhus, Denmark. The optical, mechanical and vacuum design will be described along with results on the resolving power of the monochromator which have been obtained scanning across rare gas resonance lines at various energies. Based on these results we will conclude that the monochromator is mechanically very stable and reproducible and behaves according to its specifications with resolving powers between 10000 and 20000, i.e. bandwidths of a few meV only. J. Feldhaus, E. L. Saldin, J. R. Schneider, E. A. Schneidmiller, and M. V. Yurkov, Opt. Commun. 140, 341 (1997)
	Slides

WEBAU04	Single-Shot Longitudinal Bunch Profile Measurements at FLASH Using Electro-Optic Detection: Experiment, Simulation, and Validation	laser, 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

WEPPH003	Magnetic Measurements of the FLASH Infrared Undulator	undulator, simulation, radiation, 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.

WEPPH005	Magnet Sorting for the European XFEL Hybrid Undulator - Comparing Study	undulator, controls, free-electron-laser, 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.

WEPPH006	Study of Undulator Deformation Tolerance for the European XFEL	undulator, simulation, radiation, 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.

WEPPH008	Measurements of Projected Emittances at FLASH	emittance, undulator, linac, lattice	338
	F. Loehl, E. Prat DESY, Hamburg K. Honkavaara Uni HH, Hamburg
	FLASH is a SASE FEL user facility at DESY (Hamburg) operating with photon wavelengths in the range from vacuum ultraviolet to soft x-rays. Although the slice emittance is a more appropriate parameter to characterize the SASE process, the projected emittance provides a useful measure of the electron beam quality. At FLASH the projected emittance is measured at three location along the linac: in the injector (130 MeV), after the collimator (full electron beam energy), and in the undulator section. The transverse beam shape is measured with OTR monitors and wire scanners. The multi-monitor method is used to determine the emittance. In this paper we describe the measurement set-up and procedure and report recent results and planned upgrades.

WEPPH009	Recent Measurements of the Longitudinal Phase Space at PITZ	gun, booster, simulation, 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.

WEPPH011	Photocathode Laser Pulse Diagnostics at PITZ	laser, cathode, diagnostics, 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, laser, 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.

WEPPH015	Modeling of a Laser Heater for Fermi@Elettra	laser, undulator, 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	laser, cathode, vacuum, gun	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.

WEPPH018	A High Brightness X-band Split Photoinjector Concept and Related Technological Challenges	gun, emittance, brightness, klystron	370
	D. Alesini, M. Migliorati, L. Palumbo, B. Spataro, M. Ferrario INFN/LNF, Frascati (Roma) J. B. Rosenzweig UCLA, Los Angeles, California L. Serafini INFN-Milano, Milano
	Future light sources based on high gain free electron lasers, require the production, acceleration and transport up to the undulator entrance of high brightness (low emittance, high peak current) electron bunches. Wake fields effects in accelerating sections and in magnetic bunch compressors typically contribute to emittance degradation, hence the photo-injector design and its operation is the leading edge for high quality beam production. The state of the art photoinjector beam brightness can be in principle brought above the 10¹⁵ A/m² threshold with an X-band gun and a proper emittance compensation scheme. We discuss in this paper an optimized design of a split X-band photoinjector, a convenient matching scheme with the downstream linac, based on the SPARC project experience, and the further technological developments required to reach such an appealing goal.

WEPPH019	Determination of the Wakefield Budget for the FERMI FEL Undulator System	vacuum, undulator, impedance, coupling	374
	C. Bontoiu, P. Craievich, L. Rumiz ELETTRA, Basovizza, Trieste M. Castronovo Università degli Studi di Trieste, Trieste R. Vescovo, A. A.G. Lutman DEEI, Trieste
	The FERMI project aims to achieve very high-brightness photon beam pulses of minimum bandwidth. These goals can be marred by the presence of large wakefields generated along the length of the undulator small-gap vacuum chamber. Estimations of the induced energy-spread caused by the resistive wall and surface roughness wakefields along the length of the vacuum chamber of the FERMI FEL undulator are presented. The energy spread and losses induced by the resistive wall wakefield are determined for three possible transverse geometries of the vacuum chamber, namely circular, rectangular and elliptical cross-section, while the energy spread and losses induced by the surface roughness wakefields are obtained for the circular cross-section case. In this last case in-house surface profile measurements are used to provide realistic estimates.

WEPPH021	Wide Band Seeding and Wavelength Compression	laser, 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.

WEPPH023	Beam Properties from S-band Energy Compensated Thermionic RF Gun and Linac for KU-FEL	emittance, gun, free-electron-laser, klystron	386
	K. Masuda, H. Ohgaki, S. Sasaki, T. Shiiyama, H. Zen, T. Kii Kyoto IAE, Kyoto
	Energy degradation arising from back-bombardment effect was quite serious problem for using a thermionic RF gun as injector of FEL device. Thus we have developed energy compensation technique, which keeps cavity voltage as constant by controlling input RF power to the RF gun. We have successfully extracted electron beam with constant energy from the thermionic RF gun with the energy compensation technique. However, PFN tuning of the Klystron modulator and time-varying beamloading would affect macro-pulse properties; energy spread, emittance, phase mismatch between RF gun and accelerator, etc. Thus we have estimated effects to the beam properties by using the 1D thermal conduction model* and PARMERA, and also evaluated these properties experimentally. The estimated and measured results were not so serious for KU-FEL system. We will discuss the comparison between the experimental results and the calculation results in this conference. * N. Okawachi, et al., Proc. of the FEL 2006, pp.664-667 (2006)** T. Kii, et al., Nucl. Instr. and Meth. A 483 310-314 (2002)

WEPPH024	Numerical Evaluation of Oscillator FEL with Multi-Bunch Photo-Cathode RF-gun in Kyoto University	gun, undulator, laser, 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).

WEPPH025	Progress in the FEL Lasing in Kyoto University	cathode, undulator, gun, alignment	394
	T. Kii, K. Masuda, H. Ohgaki, T. Shiiyama, H. Zen, S. Sasaki Kyoto IAE, Kyoto
	We have constructed an infrared (4～13μm) FEL facility for advanced energy researches in Kyoto University. The numerical studies on the expected FEL gain, which was based on the experimental measurements both of the undulator and of the electron beam parameters, were carried out. However, g-parameter of the mirror cavity was located close to the unstable region. In order to obtain a stable FEL, we calculated the FEL gain taking into account the duct shape, the tilt angle, and the offset of the mirror, then for the first lasing the mirror parameter was optimized. At the present stage, we have installed the undulator and the mirror cavity. A spectrum of the spontaneous emission was measured, which was consistent with the result of spectrum calculation obtained with measured magnetic field of the undulator. In this conference, we will present the result of the mirror optimization, and measurement of the spontaneous emission. The status of the experiment on FEL lasing will also be addressed. M. Nakano, et al., Proceedings of the 2006 FEL conference, (2006)

WEPPH026	Design Study of the Triode-Type Thermionic RF Gun	cathode, gun, coupling, emittance	398
	K. Kanno, E. Tanabe AET Japan, Inc., Kawasaki-City T. Kii, K. Masuda, H. Ohgaki, S. Sasaki, H. Zen, T. Shiiyama Kyoto IAE, Kyoto
	We use a 4.5-cell RF gun with a thermionic cathode as the injector for our KU-FEL facility, having taken its advantageous features compared with photocathode guns, such as high averaged current, low cost and easy operation, while we suffer from the limited macro-pulse duration and peak current by the back-bombardment effect. To mitigate these adverse effects, we proposed the triode-type thermionic RF gun with an additional small cavity providing the accelerating phase nearby the cathode independent of the main cavity phase. Results from PIC simulations show that the back-bombardment power can be reduced drastically by more than 80%, and in addition the peak current of the output electron beam will be improved greatly by supplying a moderate RF power of tens kW to the RF triode structure. The RF system of up to 100 kW capabilities has been prepared and tested. Also the prototype design of the triode-type thermionic RF gun was completed. The cavity parameters, namely the quality factor, shunt impedance, and the coupling coefficient with the RF feed coaxial cable were designed taking into account both the available maximum field on the cathode and the phase and amplitude stability against the expected variations of the beam loading and cavity temperature. We will also present PIC simulation prediction on the output beam characteristics promising the first FEL lasing. K. Masuda, et al., Proceedings of the 2006 FEL conference, (2006)

WEPPH027	Beam Diagnostics for the First Lasing of the KU-FEL	gun, emittance, simulation, 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).

WEPPH028	Development of a Compact Cherenkov Free-Electron Laser Operating Terahertz Wave Range	radiation, vacuum, cathode, free-electron-laser	406
	M. R. Asakawa, N. M. Miyabe Kansai University, Osaka A. Ikeda, M. Kusaba, Y. Tsunawaki OSU, Daito, Osaka
	We designed a compact Cherenkov Free-Electron Laser(CFEL) device capable of delivering mW-level output power at frequencies of up to THz from 10GHz to 1 THz. CFEL has the advantage of generating higher frequencies at lower electron beam energy. Due to lower electron beam CFEL device is compact. Our CFEL device consists of a waveguide partially filled with two lined parallel dielectric slabs through which a relativistic electron beam propagates. We call this structure "double-slab". In our device, the electron beam is generated using the Spindt cathode. We used a super conducting magnet to compress and guide the electron beam along the dielectric slabs. Assuming a dielectric slab thickness of 0.65mm,length of 11cm and electron beam energy 50keV ,the output power generated by the device was numerically calculated to be mW-level at 46GHz. Currently , we are conducting the POP experiment at millimeter wave range.

WEPPH029	Development of the Longitudinal Phase-Space Monitor for the L-band Electron Linac at ISIR, Osaka University	photon, radiation, linac, vacuum	409
	T. Igo, G. Isoyama, S. Kashiwagi, M. Morio, R. Kato ISIR, Osaka
	The correlation between longitudinal positions of electrons in a bunch and their energies has a critical effect on the temporal evolution of SASE, and various methods are being developed to measure the longitudinal phase-space profile. We are developing a system to measure the longitudinal phase-space distribution of electrons by a combination of a bending magnet, a profile monitor, and a streak camera at the Institute of Scientific and Industrial Research (ISIR), Osaka University. In the preliminary experiments using a profile monitor utilizing optical transition radiation (OTR), it was confirmed that the monitor had higher momentum resolution than the presently used momentum analyzer consisting of a slit and a current meter. However, we could not obtain the sufficient number of photons to obtain the phase-space image since, in addition to a low photon yield, the angular distribution of OTR emitted by the electron beam in the energy region of 10 – 20 MeV, with which THz-SASE and THz-FEL experiments are conducted at this laboratory, is too large to concentrate it efficiently on a streak camera. In order to increase the number of photons, we try to use silica aerogel as a radiator of the profile monitor by following the example of PITZ. We will present an outline of the phase-space monitor we are developing and its experimental results. R. Kato et al, FEL’06, Berlin, Germany, August 2006, THPPH041, p.676, http://www.jacow.org.** J. Roensch et al, FEL’06, Berlin, Germany, August 2006, THPPH019, p.597, http://www.jacow.org

WEPPH030	Development of a Precise Timing System for the ISIR L-Band Linac at Osaka University	linac, laser, gun, 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.

WEPPH031	Development of A Low Emittance DC Gun for Smith-Purcell BWO FEL	emittance, gun, cathode, simulation	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, linac, simulation, 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.

WEPPH034	Fourier and Non-Fourier Models for Photoemission	laser, 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.

WEPPH037	Coherence of Space Charge Vibrarion and Parameters of Electron Guns	gun, emittance, space-charge, cathode	432
	S. V. Miginsky BINP SB RAS, Novosibirsk
	Space charge effect always determines the motion of particles in electron guns. Coherence of space charge vibration leads to oscillation of the emittance along a gun or a charge affected beamline. This phenomenon is closely related to a technique known as emittance compensation. These phenomena together with others (non-coherent) have been considered in the paper. The optimal parameters of guns and the expected emittance of the beam from the optimal ones have been estimated and scaled.

WEPPH038	Low Power Consuming Hybrid Bending Magnet at the XFEL Beam Dump	permanent-magnet, dipole, laser, 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	laser, undulator, 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	laser, undulator, 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, laser, free-electron-laser, 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, laser, cathode, vacuum	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	laser, radiation, vacuum, 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, photon, laser, 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.

WEPPH049	Test of a Wiresanner in the Diagnostic Section of PITZ	diagnostics, cathode, undulator, background	461
	G. Asova, J. W. Baehr, J. H. Han, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, V. Miltchev, A. Oppelt, B. Petrosyan, M. Sachwitz, L. Staykov, F. Stephan, H.-J. Grabosch DESY Zeuthen, Zeuthen
	The Photo Injector Test facility at Zeuthen (PITZ) has been established to optimize electron beams of high brilliance needed for short wavelength FELs. In a first step one wire scanner station, developed and used in the undulator section of FLASH at DESY, was tested in the diagnostic section of PITZ. Measurements of the beam-profile and the beam-position were performed to test the useability of such type of wire scanner at PITZ. The obtained results are presented and discussed. The test has shown that wire scanners of this type can be used successfully as complementary measurement device for beam-profile measurements at PITZ. In the final state of extension of PITZ , two wire scanners are foreseen as standard diagnostic tools.

WEPPH051	Development of a Beam Current Transformer for the X-FEL Project in SPring-8	dumping, klystron, damping, controls	464
	H. Maesaka, Y. Otake, A. Higashiya RIKEN Spring-8 Harima, Hyogo
	The SCSS prototype accelerator has been constructed at SPring-8. The output signal of the current transformer (CT) for measuring an electron beam current in SCSS prototype accelerator has a few megahertz noise emitted from the thyratron of klystron modulator, a ringing signal caused by the weak field of the electron beam. The long period undulation of an electrical ground level at the CT output also occurred by a large electric current generated by the klystron modulator, and flown into the ground. As a result, it is difficult to measure the beam current correctly. Therefore, we devised a new CT monitor in order to improve the problem as mentioned above. The improvement points are below. The thyratron noise was reduced by contacting between the ground of the CT case and the outer surface of a CT signal cable. The ringing signal was suppressed by intercalating dumping resistance material into the space between the case and the ferrite core of CT. We think that the undulation of ground level could be common mode noise and devised how to modulate the undulation. In this paper, we introduce the improvement points, and the obtained waveform of the CT signal as result.

WEPPH052	In-situ Undulator Field Measurement with the SAFALI System	undulator, laser, feedback, vacuum	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	laser, 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.

WEPPH054	Coherent THz Light Source Using Very Short Electron Bunches from a Thermionic RF Gun	gun, undulator, radiation, simulation	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

WEPPH055	Experimental Investigation of Smith-Purcell Radiation From Gratings of Different Profile	target, radiation, vacuum, microtron	480
	V. A. Cha, D. V. Karlovets, Yu. A. Popov, A. Potylitsyn, L. G. Sukhikh, G. A. Naumenko TPU, Tomsk B. N. Kalinin, G. A. Saruev INPR, Tomsk
	Smith-Purcell radiation (SPR) is widely considered as the spontaneous mechanism for FEL. There are a few theoretical SPR models, which predict large difference between radiation intensity from relativistic electrons for grating with different profile. To choose the most effective grating we carried out the absolute coherent SPR intensity measurements on the 6.2 MeV electron beam. The coherent SPR spectra and angular distributions were investigated. Gratings with lamellar, triangular and so-called "flat" gratings were studied. It was shown the grating consisted of the conductive strips is more preferable target for SPR generation.

WEPPH056	Gain and Coherence Enhancement for SASE FEL using Laser pre-modulated Electrons	bunching, acceleration, wiggler, radiation	484
	H.-L. Chang, C. H. Chen, W. C. Cheng, A.-C. Chiang, Y.-C. Huang NTHU, Hsinchu W. K. Lau, G.-H. Luo NSRRC, Hsinchu
	SASE FEL built up from shot noises exhibits noisy temporal and spectral structures at the output. We propose to use a laser to modulate the electron density at low beam energy and improve the emission characteristics of the SASE FEL at high beam energy. In this scheme, a laser beat wave is incident on the photocathode of an electron gun to generate periodically bunched electrons at the beat-wave frequency. The density modulated electrons can generate superradiance at the harmonics of the beat frequency in all types of single-pass FEL, including Smith-Purcell FEL, Cherenkov FEL, and undulator FEL. The bunching frequency can be further increased by a factor of 10-100 by compressing a chirped, density-modulated, low-energy electron pulse in an alpha magnet, which is subsequently accelerated to high energy for SASE FEL. Computer simulation using particle-in-cell codes, including ASTRA, ELEGANT, and GINGER, shows significant improvements on the gain and coherence of SASE FEL. We will report our detailed study and experimental progress in the conference.

WEPPH058	Modeling a RF Linac Based Short Pulse Waveguide FEL	radiation, simulation, 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.

THAAU01	Experience and Plans of the JLAB FEL Facility as a User Facility	laser, free-electron-laser, 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

THAAU03	Experimental Study of Volume Free Electron Laser Using a "Grid" Photonic Crystal with Variable Period	radiation, free-electron-laser, 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

THBAU01	Research Highlights from FLASH	free-electron-laser, laser, 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

FRAAU01	Source of Radiation on ARC-EN-CIEL Proposal	undulator, radiation, laser, 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

FRAAU02	Status of the FEL Test Facility at MAX-lab	laser, gun, 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

FRAAU03	Compact Ring FEL as a Source of High Power Infrared Radiation	radiation, undulator, bunching, simulation	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
	Slides

FRAAU04	Re-Commissioning of the Far-Infrared Free Electron Laser for Stable and High Power Operation after the Renewal of the L-Band Linac at ISIR, Osaka University	linac, klystron, wiggler, controls	521
	T. Igo, S. Kashiwagi, R. Kato, M. Morio, G. Isoyama ISIR, Osaka
	We have been developing a far-infrared FEL since late 1980s based on the 40 MeV, L-band electron linac at the Institute of Scientific and Industrial Research (ISIR), Osaka University. The first lasing was obtained at 32~40 um in 1994 and since then we progressively modified the FEL system and continued experiment in between to expand the wavelength region toward the longer wavelength. We finally obtained lasing at 150 um in 1998. We could not obtain power saturation because the macropulse duration is 2 us, though the RF pulse is 4 us long, due to a long filling time of the acceleration tube of the L-band linac and the number of amplification times is limited to 50 only. The linac was constructed approximately 30 years ago and it was not suitable for stable and high power operation of FEL, so that we suspended the development of the FEL. In 2002, we had an opportunity to remodel the linac largely for higher stability and reproducibility of operation. We also added a new operation mode for FEL in which the macropulse duration can be extended to 8 us. I took time to remodel the linac and commission it, but finally the operation mode for FEL is being commissioned and we are resuming the FEL again after the long suspension. We will report the progress and the current status of the re-commissioning of the FEL.
	Slides