FEL 2006 - List of Keywords (emittance)

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emittance

Paper	Title	Other Keywords	Page
MOAAU04	First Lasing at SCSS	undulator, radiation, focusing, gun	16
	T. Shintake RIKEN Spring-8 Harima, Hyogo
	On 20 June, the SCSS prototype accelerator firstly generated pulses at VUV 49 nm FEL radiation, using ultra-low emittance beam provided by a newly developed single-crystal CeB6 thermionic cathode. SCSS prototype accelerator has been recently constructed in 2004-2005 at SPring-8 site in Japan, and comissioned recently. Its major purpose is to test hardware components developed at RIKEN/SPring-8 in SCSS R&D required to realize X-ray FEL at 1 Angstrom wavelength. One of the most challenging ideas in SCSS is to use CeB6 single crystal cathode to generate ultra-low emittance beam. We start from a lower beam current of 1 A from 500 kV e-gun, then we compress the bunch length more than a few 100 times to generate a few 100 A beam without deteliorating the emittance in the injector. Careful design was made on rf-cavities and magnetic lenses to perform velocity bunching in the injector system, which has been installed in the prototype accelerator. After four C-band accelerators, beam energy reaches 250 MeV. On 15 June, evening 4 pm, we firstly closed the upstream undulator, after one hour tuning, we observed narrow spectrum peaked at 49 nm in the intense VUV radiation, which was totally different from the natural undulator radiation (spontanenous mode). We performed careful measurements on various aspects, and announced "the first lasing" on 20 June.
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MOBAU05	Status of Japanese XFEL Project and SCSS Test Accelerator	electron, undulator, cathode, radiation	33
	T. Shintake RIKEN Spring-8 Harima, Hyogo
	Japanese XFEL based on SASE, aming at generating 1 A X-ray with 8 GeV e-beam, has been funded. Construction 2006-2010, beam comissioning is scheduled in 2010. In order to estabilish technology for XFEL, SCSS test accelerator, e-beam 250 MeV, 60 nm minimum wavelength, has been constructed, now under beam comissioning. We hope to be able to report the first lasing.
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MOPPH011	FELO: A One-Dimensional Time-Dependent FEL Oscillator Code	simulation, electron, radiation, undulator	59
	B. W.J. McNeil, G. R.M. Robb USTRAT/SUPA, Glasgow D. J. Dunning, N. Thompson CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
	A one-dimensional, SDDS compliant time-dependent FEL oscillator code has been developed in Fortran 90. The code, FELO, solves universally-scaled FEL equations to simulate oscillator FELs operating from the low to high gain regime. The code can simulate start-up from shot noise, different electron pulse current distributions, the effects of cavity length detuning and temporal jitter between electron bunches. Cavity detuning curves for both the low-gain IR-FEL and the regenerative amplifier VUV-FEL of the 4th Generation Light Source (4GLS) proposal at Daresbury Laboratory are modelled. The code predictions for the VUV-FEL output are compared with simulations performed with the parallel implementation of Genesis 1.3 and are found to be in good agreement.

MOPPH014	Optimization of Parameters of Smith-Purcell BWO	electron, space-charge, free-electron-laser, laser	67
	V. Kumar RRCAT, Indore (M. P.) K.-J. Kim ANL, Argonne, Illinois
	We perform a detailed study of the dependence of start current in Smith-Purcell Backward Wave Oscillators (SP-BWO) on grating parameters and electron beam parameters. In our analysis, we include the attenuation due to finite conductivity of the grating material into account and also include three-dimensional effects approximately. We perform numerical simulation to optimize the parameters of an SP-BWO in order to generate intense THz-radiation.

MOPPH030	X-Rays Generation with a FEL Based on an Optical Wiggler	laser, electron, radiation, bunching	99
	A. Bacci, C. Maroli, L. Serafini INFN-Milano, Milano M. Ferrario INFN/LNF, Frascati (Roma) V. Petrillo Universita' degli Studi di Milano, Milano
	The interaction between high-brilliance electron beams and counter-propagating laser pulses produces X rays via Thomson back-scattering. If the laser source is long and intense enough, the electron beam can bunch on the scale of the X-ray wavelength and a regime of collective effects can establish. In this case the FEL instability can develop and the system behaves like a FEL based on an optical undulator. Coherent X-rays can be irradiated, with a bandwidth thinner than that of the corresponding incoherent emission. The emittance of the electron beam and the non-uniformity of the laser energy limit the growth of the X-ray signal. We analyse with a 3-D code the transverse effects in the emission. The scalings typical of the optical wiggler make possible considerable emission also in violation of the Pellegrini criterion for static wigglers. A generalized form of this criterion is validated on the basis of the numerical evidence. An optimization of the radiation intensity has been done shifting the focus of the beam. The dependence of the radiation on the stability of the laser pulse has been studied. INFN, Section of MIlan, Via Celoria,16 20133 Milano (Italy)

MOPPH048	The ARC-EN-CIEL FEL Proposal	laser, radiation, undulator, electron	146
	C. Bruni, O. V. Chubar, J.-M. Filhol, A. Loulergue, L. Nahon SOLEIL, Gif-sur-Yvette P. Bosland, B. Carré, M.-E. Couprie, G. Devanz, D. Garzella, O. Gobert, Ph. Hollander, M. Jablonka, M. Labat, G. Lambert, M. Luong, F. Meot, P. Monot, A. Mosnier, G. Petite, O. Tcherbakoff, B. Visentin CEA, Gif-sur-Yvette J.-R. Marquès LULI, Palaiseaux H. Monard, J.-M. Ortega CLIO/ELYSE/LCP, Orsay A. Rousse LOA, Palaiseau
	ARC-EN-CIEL (Accelerator-Radiation for Enhanced Coherent Intense Extended Light aims at providing the user community with coherent femtosecond light pulses covering from UV to soft X ray in France. Phase 1 aims at exploiting the different sources of seeding, in particular Harmonic generation in Gas (HHG), to improve the longitudinal coherence and shortening the output radiation wavelength in a rather compact device. Phase 2 uses a CW 10 KHz 1 GeV superconducting linear accelerator delivering high charge, subpicosecond, low emittance electron bunches for HHG seeded High Gain harmonic Generation extending to 1 nm. In phase 3, fs undulator sources in the IR, VUV and X ray and a FEL oscillator in the 10 nm range will be implemented on ERL beam loops for beam current or energy enhancement. Electron plasma acceleration and fs hard X ray produced by Thomson Scattering are also foreseen. Preliminary studies are carried out in the frame of the EUROFEL collaboration, concerning the electro-optical measurement at ELYSE, carbon nanotubes, synchronisation and beam shaping for the gun, seeding with high harmonics produced in gas on SPARC and compensation of microphonics for the Linac.

MOPPH058	Start-to-end Time-Dependent Study of FEL Output Sensitivity to Electron-beam Jitters for the First Stage of the FERMI@Elettra Project	electron, simulation, photon, linac	178
	G. De Ninno, E. Allaria, M. Trovo ELETTRA, Basovizza, Trieste
	Sensitivity of the output laser pulse to electron-beam jitters is one of the major issues affecting the expected performance of both SASE and seeded FEL's. Focusing on the first stage of the FERMI@Elettra project, in this paper we present results of time-dependent numerical simulations in which the codes GENESIS and GINGER have been used to process a large number of electron-beam distributions generated at the gun using the code GPT and propagated through the linac using the code ELEGANT.

MOPPH063	Coherent X-Ray Production by Cascading Stages of High Gain Harmonic Generation Free Electron Lasers Seeded by IR Laser Driven High-Order Harmonic Generation	radiation, electron, laser, undulator	186
	J. Wu, P. R. Bolton SLAC, Menlo Park, California
	Coherent x-ray production achieved by seeded free electron lasing with cascaded high gain harmonic generation (HGHG) is important for next generation development of synchrotron light sources. We examine the feasibility and some features of FEL emission seeded by a high order harmonic of an intense infrared conventional laser source (HHG). In addition to the intrinsic FEL chirp phenomenon, the longitudinal profile and spectral bandwidth of the HHG seed are modified significantly by the FEL interaction well before saturation occurs. This smears out the original attosecond pulselet structure. As an example, we describe a cascaded HGHG scheme for coherent x-ray FEL generation that is seeded by the twenty-seventh harmonic of an ultrashort 800 nm laser pulse with 10 fs rms duration. Given the multiple order HHG spectrum, proof-of-principle experiments using lower order harmonics can also be considered.

MOPPH069	Transverse and Longitudinal Coherence Properties of the Radiation from X-Ray SASE FELs	radiation, electron, undulator, simulation	206
	E. Saldin, E. Schneidmiller, M. V. Yurkov DESY, Hamburg
	We present the results of comprehensive numerical studies on transverse and longitudinal coherence of SASE FEL radiation. Development of coherence in exponential gain regime and saturation is studied with the help of similarity techniques. Expected coherence properties of X-ray sourses at the European XFEL, LCLS and SCSS are compared. The simulations were performed with the three-dimensional time-dependent code FAST using a real number of particles in the electron bunch.

MOPPH072	Ultra High Brightness Accelerator Design	electron, linac, acceleration, cathode	214
	R. J. Bakker, A. Adelmann, A. Anghel, M. Dehler, R. Ganter, S. C. Leemann, K. L. Li, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, V. Schlott, F. Q. Wei, A. F. Wrulich PSI, Villigen
	The Low Emittance Gun (LEG) Project at the Paul Scherrer Institute (PSI) in Switzerland incorporates the development of an ultra low emittance electron-source to drive a cost-effective X-ray FEL. For this purpose the source is based on field-emitter technology followed by high gradient (1 MV, 0.25 GV/m) acceleration. However, even with such a design the emerging electron beam is fragile and it is not evident that the low emittance can be preserved in the following acceleration process. Here we present a concept to achieve this goal, i.e., the status of the electron source development and an overview of the acceleration concept. Emphasis is given to a 250 MeV accelerator design, which is suited to serve as an injector for an X-ray FEL at 0.1 nm (12.4 keV) and boosts the electron beam into a regime where space-charge forces become less dominant. K. Li et al., Proceedings of the FEL2005 Conference, Stanford, CA, USA, p. 483 (2005)

TUAAU05	Optical Design of the Energy Recovery Linac FEL at Peking University	linac, undulator, simulation, space-charge	277
	Z. C. Liu, J.-E. Chen, J. K. Hao, K. X. Liu, X. Y. Lu, S. W. Quan, B. C. Zhang, K. Zhao, G. M. wang PKU/IHIP, Beijing
	Peking University is currently building an Energy Recovery Linac FEL (PERFEL). The system is consisted of the DC-SC photocathode injector, the superconducting main linac which is composed of two nine cell TESLA-type cavities and the beam transport system. The objective of the PERFEL is to build a testbed for the study of beam dynamics and accelerator technology for energy recovery except to provide infrared FEL. In this paper the main parameters of the PERFEL are described and the optical design for the beam transport of PERFEL is presented. The simulation is carried out using the typical particle tracking codes such as elegant. *Corresponding author. Tel: +86-10-6275-8528; Fax: +86-10-6275-1875. Email address: kxliu@pku.edu.cn
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TUBAU06	Investigations of the Longitudinal Electron Bunch Structure at the FLASH Linac with a Transverse Deflecting RF-Structure	quadrupole, electron, linac, dipole	300
	M. Roehrs, C. Gerth, H. Schlarb DESY, Hamburg
	At the FLASH linac at DESY, electron bunches with high peak currents are produced by bunch shortening in two magnetic chicanes induced by a nearly linear energy-time gradient. Thereby the high current region of a compressed bunch is distorted by coherent synchrotron radiation and space charge forces. Consequences of these effects are a degradation of time-sliced transverse emittance, slice centroid shifts and characteristic energy-time correlations. In this paper we present measurements of the aforementioned quantities for different compression schemes with a transverse deflecting rf-waveguide (LOLA). The structure allows to establish the longitudinal density profile of single bunches on the vertical axis of an OTR-screen. The horizontal time-sliced emittance can be reconstructed from measurements of the slice widths for different quadrupole settings. By dispersing vertically streaked bunches horizontally with a dipole, the energy-time correlation can be directly obtained in a single shot measurement. The measurement results are compared to simulations.
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TUPPH038	Commissioning of S-band RF GUN and Linac for the Mark-III FEL Facility at Duke University	gun, linac, cathode, electron	411
	Y. Kim, G. Edwards, M. Emamian, J. Gustavsson, S. M. Hartman, G. Swift, P. W. Wallace, P. Wang FEL/Duke University, Durham, North Carolina
	At the Free Electron Laser (FEL) Laboratory of Duke University, there is an S-band linac based Mark III FEL facility which can supply coherent FEL photon beam in the infrared wavelength range. To supply high quality electron beams and to have excellent pulse structure, we installed a new S-band RF GUN with the LaB6 cathode for the Mark III FEL facility in 2005. Since maximum repetition rates of macropulse and micropulse are 15 Hz and 2856 MHz, respectively, our new RF GUN can generate 17142 bunches within a 6 us long bunch train, and maximum 257130 bunches within one second. In this paper, we describe recent commissioning experiences of our newly installed S-band RF GUN and Linac for the Mark III FEL facility.

TUPPH040	Emittance Compensation of Superconducting Gun and Linac System for Beams with Large Chromatic Variance	linac, focusing, gun, chromatic-effects	419
	B. Buckley Cornell University, Ithaca, New York D. Kayran, V. Litvinenko BNL, Upton, Long Island, New York
	Among the methods of emittance compensation for a superconducting rf gun and linac system include utilizing a solenoid and drift space after the gun to achieve a specific beam envelope with zero beam divergence before entrance into the linac. Studies on this method have assumed minimal energy spread in the beam. However, in cases where chromatic effects cannot be ignored this one solenoid emittance compensation technique is inadequate. Proposed is a new method of emittance compensation utilizing two solenoids in order to minimize emittance in beams with large energy spread. We present a theoretical basis for the new technique along with a computer optimized configuration. The results are compared with previous methods of emittance compensation.

TUPPH067	Commissioning of a New Emittance Measurement System at PITZ	electron, diagnostics, booster, gun	474
	L. Staykov, J. W. Baehr, H.-J. Grabosch, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, A. Oppelt, B. Petrosyan, J. R. Roensch, F. Stephan DESY Zeuthen, Zeuthen G. Asova, I. Tsakov INRNE, Sofia
	The goal of the Photo Injector Test facility in Zeuthen (PITZ) is to test and optimize high brightness electron sources suitable for FEL's like FLASH and XFEL. Such sources are characterized by very low emittance at high bunch charge. The Emittance Measurement SYstem (EMSY) described in this paper uses YAG and OTR screens to measure the transverse beam size and thin Tungsten slits to measure the divergence of the beam. It has been optimized to measure emittance for a beam of 1 nC in the energy range 5 - 30 MeV. EMSY was developed in a cooperation between DESY Zeuthen and INRNE Sofia. It was installed in the PITZ tunnel in the beginning of June and commissioning and first measurements were done.

TUPPH071	Simulation of Mirror Distortion in Free-Electron LASER Oscillators	wiggler, simulation, electron, vacuum	477
	H. Freund SAIC, McLean S. V. Benson, M. D. Shinn Jefferson Lab, Newport News, Virginia
	Thermal distortion in cavity mirrors in high-power FELs can alter mode quality and degrade performance. Hence, it is important to be able to predict the character of the distortions to model their effect on FEL performance. To this end, we address these key issues by developing modeling and simulation tools that can accomplish these goals, and then benchmarking the simulation against observations on the 10 kW-Upgrade experiment at the Thomas Jefferson National Accelerator Facility. The modeling and simulation will rely on the MEDUSA code, which is a 3-D FEL simulation code capable of treating both amplifiers and oscillators in both the steady-state and time-dependent regimes. MEDUSA employs a Gaussian modal expansion, and treats oscillators by decomposing the modal representation at the exit of the wiggler into the vacuum Gaussian resonantor modes and then analytically propagating these modes through the resonator back to the entrance of the wiggler in synchronism with the next electron bunch. Knowledge of the power loading on the mirrors allows us to model the mode distortions using Zernicke polynomials and this technique has been incorporated into MEDUSA.

THAAU03	A Scalloped Electron Beam Free-Electron Laser	wiggler, electron, radiation, simulation	509
	D. C. Nguyen LANL, Los Alamos, New Mexico W. B. Colson NPS, Monterey, California H. Freund SAIC, McLean
	Typical high-gain FEL amplifiers employ an electron beam that is matched to the wiggler so that the envelope remains constant throughout the wiggler. This paper describes a novel approach in which the electrons undergo natural betatron scalloping motion along the wiggler because the beams are deliberately mismatched at the wiggler entrance. We present an analysis of the electron scalloping motion and the FEL interaction with a scalloped electron beam. For a representative set of beam and wiggler parameters, we discuss the effect of the pinching the electron beams on the interaction in the FEL and on the focusing and propagation of the FEL radiation.
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THBAU03	How to Obtain High Quality Electron Bunches in the Presence of Normal Conducting LINAC Wake Fields	electron, linac, laser, radiation	537
	S. Di Mitri ELETTRA, Basovizza, Trieste
	The dynamics of electron beams involved in Free Electron Lasers (FELs) projects is an interplay between sources of 6-dimensional emittance dilution and methods of emittance preservation. Relatively long bunches are required for harmonic cascade seeded FELs in order to accommodate the timing jitter and the seed provided by the bunch itself at each stage of the cascade. A high quality is required from such electron beams (small transverse emittance and energy spread) together with a uniform distribution in time along the usable part of the bunch; non-linearity in the longitudinal phase space and in the transverse planes are also issues. A complex longitudinal phase space dynamics characterizes the study often in presence of by the Coherent Synchrotron Radiation (CSR) generated in magnetic compressors. This paper reviews specific problems related to the electron beam dynamics dominated by bunches of kA peak current and varying length (0.1 to 2 ps) in the presence of normal conducting linac wakefields. Methods implemented to minimize the 6-dimensonal phase space degradation are discussed. Results of high beam quality performance are illustrated with particles tracking codes.
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THPPH001	Temporal Analysis and Shape Control of UV High Energy Laser Pulses for Photoinjectors	laser, target, electron, controls	552
	D. Garzella, O. Gobert, Ph. Hollander, F. Lepetit, M. Perdrix CEA, Gif-sur-Yvette T. Oksenhendler FASTLITE, Palaiseau
	In order to obtain high brightness electron bunches and generating high power, subpicosecond XUV radiation by SASE and/or seeded FEL, the laser pulses impinging onto the photocathode require special characteristics not only in terms of wavelength and delivered energy per pulse. Temporally and spatially shaped UV pulses are needed for preventing non linear space charge forces and then minimizing the electron emittance. In the EUROFEL program framework, our goal is to obtain few picosecond, 100 μJ laser pulses in the UV (266 nm) with a totally controlled and characterized longitudinal shape varying from the "beer can" profile to the "rotation ellipsoid" one. In this paper, a survey of the studies conceived for obtaining the desired goal on the KHz, Chirped Pulse Amplification (CPA)-based Ti:Sa laser system PLFA at CEA-Saclay, is shown. These latter deal with the amplitude and phase control of the stretched laser pulses issued from an amplifier before entering the compressor and the tripling unit. The work presents the theoretical background and stresses on the existing technological bottlenecks before showing various proposed experimental set-ups and preliminary promising results.

THPPH003	A High Average Power RF-Photoinjector Gun Cavity Developed for the BESSY Soft X-ray FEL	gun, electron, laser, linac	560
	F. Marhauser, M. Dirsat, V. Duerr, A. Meseck, R. Richter, E. Weihreter BESSY GmbH, Berlin G. Asova, J. W. Baehr, H.-J. Grabosch, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, A. Oppelt, B. Petrosyan, L. Staykov, F. Stephan DESY Zeuthen, Zeuthen O. Kalekin Humboldt Universität zu Berlin, Berlin J. R. Roensch Uni HH, Hamburg F. Tonisch DESY, Hamburg
	A 1.3-GHz, high duty factor, high-repetition-rate rf photoinjector gun cavity has been developed at BESSY. RF conditioning and high-power tests have been performed at the Photoinjector Test Facility at DESY Zeuthen (PITZ). The measurement results will be presented in this paper.

THPPH006	Photocathode Laser for the Superconducting Photo Injector at the Forschungszentrum Rossendorf	laser, gun, focusing, radiation	564
	I. Will, G. Klemz MBI, Berlin F. Staufenbiel, J. Teichert FZR, Dresden
	We report on the design of the photocathode laser for a superconducting RF gun under development at the Forschungszentrum Rossendorf. The laser consists of a short-pulse oscillator, a pulse-picking Pockels cell, a linear amplifier chain and a frequency conversion stage. It generates pulses of about 5 ps duration with 13 MHz repetition rate and 1 W average power at 263 nm wavelength. Both the oscillator and the amplifiers are pumped by fiber-coupled semiconductor diodes. Nd:YLF is used as the gain medium of this laser. It introduces only small distortions on the optical wavefront of the laser beam and supports pulses of a few picoseconds duration. The beamline which transfers the laser beam to the photocathode of the RF gun has a large impact on the final beam profile. One can optimize the emittance of the electron beam by illuminating the cathode with a nearly flat-top beam profile. This is achieved by a pair of aspheric lenses and appropriate imaging optics in the beamline. Simulation of the beamline and its effect on the laser profile at the photocathode of the RF gun are also presented.

THPPH008	High Peak Current Design of a Superconducting Cavity for a SRF Photoinjector	gun, laser, booster, cathode	571
	D. Janssen FZR, Dresden F. Marhauser BESSY GmbH, Berlin V. Volkov BINP SB RAS, Novosibirsk
	In collaboration between BESSY, DESY, FZR, MBI and BINP a SRF electron gun is under development. The progress obtained in the last year is reported on this conference. The motivation for the design of a new gun cavity is the FEL project at BESSY. The electron injector of the linac should produce bunches with a charge of 2.5 nC and a transverse emittance of 1.5 mm mrad. In order to compensate the emittance expansion by space charge effects a large electric field on the cavity axis and a strong magnetic field near the cathode are necessary. The strengths of these fields are limited by the maximum magnetic surface field in superconducting cavities. We have designed a 1.5 cell gun cavity, where the magnetic field is realized by an additional RF mode (TE mode). In order to reduce third order effects of the RF fields, for the accelerating field a frequency below the linac frequency is used. The laser pulse, which creates the electron bunch, has a length of 20ps and a rise time of 2ps. In the tracking calculation the electrons start with an average energy of 1eV. For a bunch charge of 2.5 nC a transverse emittance of 1.8 mm mrad has been obtained. The maximal surface field is 160 mT.

THPPH009	Cryomodule and Tuning System of the Superconducting RF Photo-Injector	gun, cathode, vacuum, acceleration	575
	J. Teichert, A. Arnold, H. Buettig, R. Hempel, D. Janssen, U. Lehnert, P. Michel, K. Moeller, P. Murcek, Ch. Schneider, R. Schurig, F. Staufenbiel, R. Xiang FZR, Dresden T. Kamps, D. Lipka BESSY GmbH, Berlin G. Klemz DESY Zeuthen, Zeuthen W.-D. Lehmann IfE, Dresden J. Stephan IKST, Drsden I. Will MBI, Berlin
	We present the designs and report on the progress in construction and testing of the cryomodule and the tuning system for the SRF gun. The SRF gun project, a collaboration of BESSY, DESY, MBI and FZR, aims at the installation of a high average current CW photo injector at the ELBE linac with a Nb cavity. The cryostat consists of a stainless steel vacuum vessel, a warm magnetic shield, a liquid N cooled thermal shield, and a He tank with two-phase supply tube. A heater pot in the He input port will be used for He level control. The 10 kW power coupler is adopted from ELBE module. A cooling and support system for the NC photo cathode has been developed and tested. It allows the adjustment of the cathode with respect to the cavity from outside. The cryomodule will be connected with the 220 W He refrigerator of ELBE and will operate at 1.8 to 2 K. The static thermal loss is expected to be less than 20 W. Two tuners will be installed for separate tuning of the three TESLA cells and the half-cell. The tuners are dual spindle-lever systems with step motors and low-vibration gears outside the cryostat. Functionality, tuning range and accuracy have been tested in cryogenic environment.

THPPH012	Dark Current Collimation and Modified Gun Geometry for the European X-Ray FEL Project	gun, cathode, electron, acceleration	579
	J. H. Han, K. Floettmann DESY, Hamburg
	An rf field of 60 MV/m will be applied at the L-band gun of the European X-ray FEL project. Such a high rf gradient will allow to achieve a transverse emittance lower than 1 mm mrad for 1 nC electron bunches but will also produce dark current up to the order of mA. The dark current generated at the gun shows a comparable dynamics to the electron beam because the same acceleration will be furnished from the gun to the last acceleration module. The dark current might accumulate high radiation dose at the undulator and limit the long pulse operation of the SASE. To reduce dark current before the first acceleration module, a new design of gun cavity and collimator is proposed.

THPPH013	Impact of the Cathode Roughness on the Emittance of an Electron Beam	cathode, electron, space-charge, gun	583
	M. Krasilnikov DESY, Hamburg
	An RF photo injector for the European XFEL should produce electron beams with normalized transverse emittance under 1 mm mrad. In order to achieve this high performance of the electron source the electric field at the photo cathode has to be increased up to 60 MV/m. The emittance budget of the optimized XFEL photo injector contains a significant part of thermal (intrinsic) emittance. A roughness of the cathode could lead to an additional uncorrelated divergence of the emitted electrons and therefore to an increased thermal emittance. The cathode roughness has been modeled using an analytical approximation and numerical simulations. The influence of the roughness parameters and the increase of the electric field have been studied.

THPPH020	Design of the Multipurpose Dispersive Section at PITZ	quadrupole, electron, dipole, booster	601
	S. Khodyachykh, J. W. Baehr, M. Krasilnikov, A. Oppelt, L. Staykov, F. Stephan DESY Zeuthen, Zeuthen T. Garvey LAL, Orsay D. Lipka BESSY GmbH, Berlin J. R. Roensch Uni HH, Hamburg
	A detailed knowledge of the parameters of a high-brightness electron beam is of major importance for evaluating the performance of a free electron laser using the beam. Therefore, a full characterization of the beam parameters is required during the commissioning of RF photoinjectors. Contributing to this task, at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) a multi-purpose high energy dispersive arm (HEDA1) for electron energies up to 40 MeV is presently under construction. The dispersive section is designed such that it will combine the functionality of 1) an electron spectrometer, 2) a device for characterization of the longitudinal phase space, and 3) a transverse slice emittance measuring system. The HEDA1 consists of a 180° dipole magnet (C-Bend), followed by a slit, a quadrupole magnet, and a screen station with a read-out for the streak camera. Design considerations and the detailed lay out of the high-energy dispersive section will be presented.

THPPH021	Design Consideration of the RF Deflector to Optimize the Photo Injector at PITZ	diagnostics, simulation, kicker, single-bunch	605
	S. A. Korepanov, S. Khodyachykh, M. Krasilnikov, A. Oppelt, F. Stephan DESY Zeuthen, Zeuthen V. V. Paramonov RAS/INR, Moscow
	In order to optimize photo injectors for Free Electron Laser (FEL) applications, a detailed characterization of the longitudinal and transverse phase space of the electron beam provided by the Photo Injector Test Facility at DESY in Zeuthen (PITZ) is required. Design considerations of the RF deflecting cavity for transverse slice emittance and longitudinal phase space measurements are presented in the paper.

THPPH027	Ramping Longitudinal Distribution Studies for the FERMI@ELETTRA Injector	space-charge, cathode, electron, linac	621
	G. Penco, M. Trovo ELETTRA, Basovizza, Trieste S. M. Lidia LBNL, Berkeley, California
	In the Fermi Linac optimization studies it comes out the request to have at the exit of the photoinjector a linear ramp in the current distribution along the bunch as alternative option with respect to the flat-top. This requirement is translated in the photoinjector optimization in a big issue. In fact the longitudinal bunch profile at the exit of the photoinjector is affected by the strong non linearity of the space charge fields at the cathode and in the drift between the gun and the first booster. The knowledge of the space charge fields at the cathode plays in important role in finding the optimum driven laser pulse shape. At this purpose an analytical description of the space charge fields produced by a bunch with an arbitrary current distribution at the cathode is provided. Space charge codes (GPT and ASTRA) have been used to evaluate the evolution of several ramping profiles from the cathode to the entrance of the first booster and the results are presented in this paper.

THPPH028	Further Studies in the FERMI@ELETTRA Photoninjector Optimization	laser, gun, linac, electron	625
	M. Trovo, G. Penco ELETTRA, Basovizza, Trieste S. M. Lidia LBNL, Berkeley, California
	In the framework of the FERMI@ELETTRA project we are presently studying an electron beam configuration satisfying the bunch energy requirements coming out from the FEL photon production system. The multi-particles tracking code results concerning the photoinjector set up which includes the RF gun and the first two accelerating sections are presented in this paper, describing two possible electron bunch configurations, which satisfy the FEL operation modes. Both injector configurations aim to match the linac requirements to have a ramped current profile at the exit of the photoinjector. Moreover sensitivity studies, time and energy jitters estimations are presented for both cases.

THPPH031	Commissioning of the SPARC Photo-Injector	laser, gun, diagnostics, controls	637
	M. Bellaveglia, D. Alesini, S. Bertolucci, M. E. Biagini, R. Boni, M. Boscolo, M. Castellano, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, M. Ferrario, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, S. Guiducci, M. Incurvati, C. Ligi, M. Migliorati, A. Mostacci, L. Palumbo, L. Pellegrino, M. A. Preger, R. Ricci, C. Sanelli, F. Sgamma, B. Spataro, F. Tazzioli, C. Vaccarezza, M. Vescovi, C. Vicario INFN/LNF, Frascati (Roma) A. Bacci, I. Boscolo, F. Broggi, S. Cialdi, D. Giove, M. Mauri, A. R. Rossi, L. Serafini INFN-Milano, Milano L. Catani, E. Chiadroni, A. Cianchi, S. Tazzari INFN-Roma II, Roma L. Giannessi, M. Quattromini, A. Renieri, C. Ronsivalle ENEA C. R. Frascati, Frascati (Roma) M. Mattioli, P. Musumeci, M. Petrarca INFN-Roma, Roma A. Perrone INFN-Lecce, Lecce J. B. Rosenzweig UCLA, Los Angeles, California
	The SPARC project is born to perform R&D activity headed to realize SASE-FEL experiments at 500nm and higher harmonic generation. The project foresees the realization of a high brightness photo-injector able to produce a 150-200MeV electron beam to drive FEL process inside a dedicated 14m long undulator. The machine is going to be assembled at LNF and its final configuration is made up of an RF gun, driven by a Ti:Sa laser, injecting into three SLAC type accelerating sections. Nowadays we are working in a photo-injector test phase, aiming to characterize the main hardware components and to investigate the behavior of the e-beam dynamics in the first meters of drift. To do this we utilize the emittance-meter, a home designed diagnostic device placed just after the RF gun, able to move 1.2 meters along the longitudinal axis to measure beam parameters. In this paper we report a more accurate description of the project, the status of the single systems constituting the machine and the most important results we obtained in the e-meter phase.

THPPH032	Free Electron Laser Triggered Photo-Cathode	cathode, laser, radiation, electron	641
	E. Sabia, A. Dipace ENEA Portici, Portici (Napoli) G. Dattoli ENEA C. R. Frascati, Frascati (Roma)
	The possibility of realizing a FEL triggered photocathode has been proposed long time ago and the advantages have been pointed out. In these devices the FEL can be exploited to extract electrons from a photocathode to provide a high quality e-beam. The device becomes even more appealing if photo-thermoionic cathodes can be exploited in two different phases. In the first the electrons are extracted from the cathode working as thermoionic and are used to drive a FEL oscillator, the FEL light is then used to flash the cathode which operates as a photo thermal assisted device. We comment on the possibility of using FEL triggered photocathodes to produce high quality e-beams for SASE or oscillator FEL devices. The use of the same e-beam driving the photocathode and the FEL makes the system naturally free of any synchronization problem arising when an external laser is used. Examples of interplay between the generation of electron and optical bursts are also investigated.

THPPH034	Laser Pulse Length Dependence of Beam Emittance of Photocathode RF-Gun	laser, electron, gun, simulation	649
	H. Dewa, T. Asaka, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T. Taniuchi, H. Tomizawa, K. Yanagida JASRI/SPring-8, Hyogo-ken
	A pulse length of the UV laser is an important parameter of the Photocathode RFgun. Due to space charge effect, too short laser pulse increases the beam emittance. Therefore there should be an optimum pulse length if the electron beam charge is determined. To study the pulse length dependence of the beam emittance, the emittance was measured at several conditions of laser pulse length, which were prepared with a laser pulse stacker. The laser pulse can be stretched by dividing a laser pulse of a few pico second into two pulses and then combined them with time delay. The pulse stacker that consists of four sets of the divider and combiner could generate an arbitrary pulse length within 2 - 20 ps by changing delay time of each sets. The beam charge dependence was also measured. Beam emittance was measured with the magnetic quadrupole scanning technique. The results are compared with predictions of a 3-D beam tracking simulation that treats space charge effects.

THPPH036	Design Study of RF Triode Structure for the KU-FEL Thermionic RF Gun	gun, cathode, simulation, electron	656
	K. Masuda, T. Kii, K. Kusukame, H. Ohgaki, T. Shiiyama, T. Yamazaki, K. Yoshikawa, H. Zen Kyoto IAE, Kyoto
	Thermionic rf guns show advantageous features compared with photocathode ones such as easy operation, low cost and high averaged current, which are suitable for their application to FELs for various uses. They however suffer from the back-bombardment effect, resulting in limited macro-pulse duration of severalμseconds. Against this adverse effect, we plan to introduce the triode structure,* in the 4.5-cell rf gun for the KU-FEL by replacing the thermionic cathode by an assembly of a cathode with an additional coaxial cavity. Two-dimensional simulations have predicted a significant reduction of the back-bombardment power by 99% with a moderate rf power of several tens kW fed to the additional extraction cavity. Moreover an improved energy spread and peak current are expected at the same time with an optimal geometry and operating conditions. * E. Tanabe et al., Proc. of 27th Linear Accelerator Meeting in Japan (2002) 57, in Japanese. ** K. Masuda et al., Proc. of 27th Intnl. FEL Conf. 2005 (2006) 588.

THPPH039	Experimental Study on Effect of Energy Distribution on Transverse Phase Space Tomography	electron, simulation, gun, quadrupole	668
	H. Zen, T. Kii, K. Masuda, M. Nakano, H. Ohgaki, N. Okawachi, S. Sasaki, T. Shiiyama, T. Yamazaki, K. Yoshikawa Kyoto IAE, Kyoto
	Tomographic method * using a quadrupole magnet and a beam profile monitor is useful method of transverse phase space measurement. However the method is suffered from energy distribution. Therefore we have evaluated the effects numerically. As the result, the low energy tail of the beam distorted the result of tomographic method even with a small amount of the tail *.To confirm the numerical evaluation, measurements have been performed with single slit method, whose result is free from energy distribution. In this conference, the experimental result of two methods will be shown and a new tomographic analysis, which mitigates the effect of energy distribution, is proposed. C. B.McKee, et al, NIM A 358 (1995) 264** H. Zen, et al, Proc. of FEL2005 (2006) 592

THPPH042	A Compact Low Emittance DC Gun Employing Single Crystal Cathode of LaB6	cathode, electron, gun, simulation	680
	K. Kasamsook, K. Akiyama, H. Hama, F. Hinode, M. Kawai, T. Muto, K. Nanbu, T. Tanaka, M. Yasuda Laboratory of Nuclear Science, Tohoku University, Sendai
	Development of an electron gun capable of producing low emittance is in the interests of further applications of high brightness electron beam such as Smith-Purcell radiation for examples. A prominent point of this DC gun is that operation high voltage is very low and the emittance is, however, sufficiently low because of a short distance between the wehnelt and the anode. A pulsed high voltage of 50 kV is supplied, and pulse duration is variable from 1 to 5 sec. Since a higher beam current of the macropulse is required in general, a cathode should have higher current density, while the smaller size of the cathode is preferred for lower emittance. Consequently we have chosen single crystal LaB6 as the cathode, which can provide higher current with good homogeneity emission. In additon, a floating bias voltage can be applied between the cathode and the wehnelt to optimize the electric field for achieving the lowest emittance. Numerical calculations using EGUN shows a better normalized rms emittance is expected to be less than 5 mm mrad. A state-of-the-art electron source will possibly open new scientific opportunities in the many fields.

THPPH043	Stable RF Phase Insensitive to the Modulator Voltage Fluctuation of the C-band Main Linac for SCSS XFEL	klystron, linac, acceleration, electron	684
	J.-S. Oh, T. Hara, T. Inagaki, J.-S. Oh, T. Shintake, K. Shirasawa RIKEN Spring-8 Harima, Hyogo
	The SCSS (SPring-8 Compact SASE Source) XFEL requires extremely stable RF system in both amplitude and phase. The fluctuation of RF output is mainly caused by modulation of the klystron beam-voltage pulse, which is directly governed by the charging stability of a klystron modulator. During R&D study on beam stability, we found a special operation point, where the beam energy gain is insensitive to the modulator voltage fluctuation. This phase can cancel out the both fluctuations and provide constant accelerating field. The stable phase depends on the klystron parameters such as the length of drift tube, operating voltage, efficiency. It is about 9 degree in case of the C-band main linac for SCSS XFEL. The bunch length after bunch compressor is so short that additional longitudinal energy spread due to the RF curvature is about 5% of the one caused by the longitudinal wake field. The particle energy is high enough so that longitudinal defocusing is negligible. The reduction of beam energy due to off-crest acceleration is less than 2%. This paper shows the analytical relation of the stable phase. ELEGANT simulation shows no appreciable degradation of the slice parameters.

THPPH046	Preliminary Measurement of Emittance Evolution Using Emittance Meter at the PAL	laser, gun, cathode, space-charge	695
	J. H. Park, J. Y. Huang, C. Kim, I. S. Ko, Y. W. Parc, S. J. Park PAL, Pohang, Kyungbuk X. Dao TUB, Beijing X. J. Wang BNL, Upton, Long Island, New York
	A high-brightness electron beam is emitted from a RF photocatoode gun with 1.6 cell cavity from October 2005 at the Pohang Accereator Laboratory (PAL). The project of 4th Generation Light Source (4GLS) with the Spontaneous Amplification Sponteneous Emission Free-electron Laser (SASE FEL) in the PAL is called Pohang Accereator Laboratory X-ray Free-electron Laser (PAL-XFEL). In order to success of the PAL-XFEL project, it is necessary to research the high-brightness electron beam at the injector. A emittance meter (E-Meter) is installed for the high-brightness research in GTS (Gun Test Stand). The measurement of transverse emittance and beam size profile along the longitudinal direction was done by the E-Meter. Precise measurement of the emittance profile will provide powerful tool for the commissioning of the 4GLS injectors based on the emittance compensation principle. We are going to achieve this with the use of slit-based E-Meter that can be moved along the longitudinal direction. In this article, we present a preliminary measurement of the emittance evolution with the E-Meter for the commissioning of the RF photocathode gun.

THPPH053	3-D Laser Pulse Shaping for Photoinjector Drive Lasers	laser, simulation, electron, gun	703
	YL. Li ANL, Argonne, Illinois X. Chang BNL, Upton, Long Island, New York
	We discuss techniques for 3-D laser pulse shaping aimed at improving the performance of photoinjectors and hence free-electron lasers seeded by the electron beams from such photoinjectors. These techniques are based on laser phase-space manipulation in conjunction with refractive/diffractive optics. We present a few schemes for 3-D laser pulse shaping that can be used to generate ellipsoidal laser pulses. Simulation results based on physical optics will be given.

THPPH058	Beam Spreading and Emittance Oscillation of an Intense Magnetized Beam in Free Space	space-charge, focusing, electron, booster	721
	C.-X. Wang, K.-J. Kim ANL, Argonne, Illinois
	Intense beams with large angular momentum have important applications in electron cooling and in producing flat beams suitable for ultrafast x-ray generation, Smith-Purcell radiators, and possibly for a future linear collider. To gain basic understanding of the influence of beam angular momentum in an otherwise space-charge-dominated beam, the behavior of such a beam in free space will be examined here, in particular, beam spreading due to space-charge force, as well as emittance oscillation. Drift space is an important part of a split photoinjector and plays a significant role in emitance compensation of a high-brightness photoinjector.

THPPH068	The Development and Application of a Photoemission Model for Cesiated Photocathode Surfaces	scattering, brightness, electron, laser	744
	K. Jensen, J. L. Shaw, J. E. Yater NRL, Washington, DC D. W. Feldman, N. A. Moody IREAP, College Park, Maryland P. G. O'Shea University Maryland, College Park, Maryland
	A photoemitter capable of in situ rejuvenation with a high quantum efficiency (QE) is a photocathode candidate of FELs and linear accelerators. Our program to develop a controlled porosity dispenser (CPD) photocathode* led to the development and validation of a theoretical model that accounts for low work function surfaces from submonolayer coverage of alkali (and alkali earth) metals. Here, we substantially modify our previous theoretical thermal photoemission model by: first, considering the impact of electron-electron and electron-lattice scattering; second, by the development of an integrated absorption-transport-emission model developed to evaluate the moments of the electron emission distribution function; and third, by the inclusion of quantum effects and surface features on the emission probability. For the experimental conditions to which we compare the resultant theory, there are no adjustable parameters. We discuss the performance of the model in the prediction of the QE of bare metals and coated surfaces, project the performance to regimes of interest to FELs, and use elements of the model to assess theoretical quantities of interest such as emittance. N. A. Moody, et al. (this conf.); K. L. Jensen, et al., (to be published in JAP99); * K. L. Jensen, et al., APL88, 154105 (2006), ibid, 164105.

THPPH070	Optimum Beam Creation In Photoinjectors Using Space-Charge Expansion	laser, simulation, space-charge, linac	752
	M. P. Dunning, A. M. Cook, R. J. England, J. B. Rosenzweig UCLA, Los Angeles, California M. Bellaveglia, M. Boscolo, L. Catani, A. Cianchi, G. Di Pirro, M. Ferrario, D. Filippetto, G. Gatti, L. Palumbo, C. Vicario INFN/LNF, Frascati (Roma) S. M. Jones Jet Propulsion Laboratory, Pasadena, California P. Musumeci INFN-Roma, Roma
	It has recently been shown that by illuminating a photocathode with an ultra-short laser pulse of appropriate transverse profile, a uniform density, ellipsoidally shaped bunch is dynamically formed, which then has linear space-charge fields in all dimensions inside of the bunch. We study here this process, and its marriage to the standard emittance compensation scenario that is implemented in most modern photoinjectors. It is seen that the two processes are compatible, with simulations indicating that a very high brightness beam can be obtained. The scheme has produced stimulus for a series of experiments at the SPARC injector at Frascati in 2006-2007. An initial time-resolved experiment has been performed involving Cerenkov radiation produced at an aerogel. We discuss the results of this preliminary experiment, as well as plans for future experiments to resolve the ellipsoidal bunch shape at low energy. Future measurements at high energy based on fs resolution RF sweepers are discussed, and prospects for using the very low longitudinal emittance beam in a future bunch compressor to produce 10 micron long beams are evaluated.

THCAU01	Overview on Diagnostics for X- and XUV-FELs	radiation, diagnostics, laser, electron	761
	B. Schmidt DESY, Hamburg
	Controlling and optimizing the SASE process of X-FELs and XUV-FELs requires detailed knowledge and information about the parameters of the driving electron beam which are of critical influence on the laser performance. Due to the very high peak current, collective phenomena have to be carefully measured and controlled while integral (projected) parameters are of limited use. This necessitates the development of a variety of diagnostics tools to monitor the electron bunch parameters in detailedness beyond the capabilities of conventional systems. Longitudinal bunch structures can be derived from time domain methods like electro optic techniques or using transverse deflecting RF-structures, and from frequency domain methods using coherent radiation. The talk will report on recent developments with special emphasis on single shot and online monitoring capabilities in this field. Other topics will be new concepts and experience in measuring the projected and time-sliced emittance of the beam, high precision beam position monitors and sub-picosecond beam phase and arrival time monitor systems.
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THCAU02	Low Emittance Injector at SCSS	electron, gun, undulator, acceleration	769
	T. Shintake, T. Hara, A. Higashiya, T. Inagaki, H. Maesaka, Y. Otake, K. Shirasawa, T. Tanaka, K. Togawa, M. Yabashi RIKEN Spring-8 Harima, Hyogo H. Baba, K. Onoe, H. Tanaka JASRI/SPring-8, Hyogo-ken H. Matsumoto KEK, Ibaraki T. Tanikawa University of Hyogo, Hyogo
	In order to realize X-ray FEL at 1 A wavelength, it is required to generate low emittance beam with high peak power. Typically 1 π-mm-mrad, and 2~4 kA beam has to obtained at undulator line. In SCSS: SPring-8 Compact SASE Source, we decided to use thermionic cathode and velocity bunching process rather than the rf-gun with photo-cathode. To verify our principle and hardwares, we constructed a test accelerator, 250 MeV, 60 nm FEL. The author reports experimental results of the test accelerator.
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	Talk

THCAU03	Operational Experience with the Emittance-Meter at SPARC	cathode, laser, gun, simulation	777
	L. Catani, E. Chiadroni, A. Cianchi INFN-Roma II, Roma M. Bellaveglia, R. Boni, M. Boscolo, M. Castellano, L. Cultrera, G. Di Pirro, A. Drago, M. Ferrario, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, F. Tazzioli, C. Vaccarezza, M. Vescovi, C. Vicario INFN/LNF, Frascati (Roma) M. Migliorati, L. Palumbo Rome University La Sapienza, Roma P. Musumeci, M. Petrarca INFN-Roma, Roma C. Ronsivalle ENEA C. R. Frascati, Frascati (Roma)
	We report the operational experience of the movable emittance meter at SPARC. This device is based on the well-known technique of pepper pot (1-D slits in our case) but it allows moving the measuring device along the beam line from about 840 mm to 2200 mm from the cathode, following the emittance oscillations. More than a simple improvement over conventional, though non-trivial, beam diagnostic tools this device defines a new strategy for the characterization of high performance photoinjectors, providing a tool for detailed analysis of the beam dynamics, over a section of the accelerator where emittance compensation take place. With this device we performed detailed and systematic studies on beam dynamics with particular attention to the transverse parameters as well as longitudinal. We report also the operating experience at the PITZ facility.
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THCAU04	Peak Current Performances from Electron Sources based on Field Emission (Single Tip and Field Emitter Arrays (FEAs))	laser, electron, vacuum, gun	781
	R. Ganter, R. J. Bakker, M. Dehler, G. J. Gobrecht, C. Gough, E. Kirk, F. Le Pimpec, S. C. Leemann, K. L. Li, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, V. Schlott, H. Sehr, S. Tsujino, A. F. Wrulich PSI, Villigen
	Reducing beam emittance while keeping high brightness is the most direct way to reduce the cost and size of Free Electron Lasers (FELs). Ultimately, beam emittance is limited by the thermal emittance at the electron source. In order to find electron sources with low thermal emittance (<5.10^-8 m.rad) and high brightness (>5.10¹³ A.m^-2.rad^-2), cathodes based on single tip field emitter as well as field emitters arrays (FEAs) are investigated. Maximum peak current, measured from single tip in ZrC with a typical apex radius around one micrometer, are presented. Voltage pulses of two nanoseconds duration and up to 50 kilovolts amplitude lead to field emission current up to 470 mA from one ZrC tip. Combination of high applied electric field with laser illumination gives the possibility to modulate the emission with laser pulses. Sub-nanoseconds current pulses have been emitted with laser pulses at 1064nm illuminating a ZrC tip under high electric field. The dependence of photo-field emitted current with the applied voltage can be explained by the Schottky effect.
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	Talk