FEL 2006 - List of Keywords (gun)

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gun

Paper	Title	Other Keywords	Page
MOAAU04	First Lasing at SCSS	emittance, undulator, radiation, focusing	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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MOPPH061	The Test Facility for Harmonic Generation at the MAX-lab Injector Linac	undulator, laser, electron, linac	182
	S. Werin, M. Brandin, T. Hansen, S. Thorin MAX-lab, Lund M. Abo-Bakr, J. Bahrdt, K. Goldammer BESSY GmbH, Berlin A. L'Huillier, J. Larsson, A. Persson, C.-G. Wahlstrom New Affiliation Request Pending, -TBS-
	The MAX-lab injector linac system will be used in a test set-up for developing and testing techniques important for the designs of the BESSY FEL and the MAX IV FEL proposals. The first goal is using a 400 MeV electron beam to generate third harmonic photons at 90 nm from a 266 nm seed laser. The installations at MAX-lab are being improved by a new photo cathode RF gun (to improve emittance and peak current), an optical klystron (2 undulators + chicane, supplied by BESSY) and a combined synchronised laser system for both the RF-gun and the seeding system. The injector optics and transport system are also being retuned to allow the necessary electron beam compression. The project is a part of the EUROFEL collaboration.

TUPPH007	JAEA Photocathode DC-Gun for an ERL Injector	electron, laser, ion, vacuum	319
	T. Nishitani, R. Hajima, H. Iijima, N. Kikuzawa, E. J. Minehara, R. Nagai, N. Nishimori, M. Sawamura JAEA/ERL, Ibaraki H. Hayashitani, Y. Noritake, M. Tabuchi, Y. Takeda Nagoya University, Nagoya
	ERL light source and FEL require an electron beam of large current and small emittance. In order to realize an electron gun satisfying such requirements, we started developments of a photocathode DC-gun and a new-type NEA-photocathode. The DC-gun consists of a chamber to activate NEA-surface, a 250keV acceleration chamber, and a mode-locked Ti:Sapphire laser. Since extreme high vacuum is essential to obtain a long-life photocathode, we adopt a load-lock system for transporting a photocathode between the chambers, each of which is equipped with an NEG pump. Up to now, we fabricated an electrodes chamber and a high voltage terminal of 250kV and we succeeded in a 250kV high voltage test. We also have suggested a superlattice photocathode as a new-type photocathode with higher performance than an existing technology. Up to now, we fabricated photocathode samples by molecular beam epitaxy and measured quantum efficiency after NEA-surface activation.

TUPPH024	Super Coherent THz Light Source Based on an Isochronous Ring with Very Short Electron Bunches	lattice, radiation, simulation, electron	371
	H. Hama, K. Akiyama, F. Hinode, K. Kasamsook, M. Kawai, T. Muto, K. Nanbu, T. Tanaka, M. Yasuda Laboratory of Nuclear Science, Tohoku University, Sendai H. Tanaka JASRI/SPring-8, Hyogo-ken
	A project to develop a coherent Teraherz (THz) light has been progressed at Laboratory of Nuclear Science, Tohoku University. The coherent synchrotron light at the frequency region of THz is emitted from electron bunches of several tens femto-second bunch length created by a thermionic RF gun and a sophisticated bunch compressor. In addition, the beam is circulating a ring consisted of nearly complete isochronous optics for many turns, so that the average power of the radiation may be considerably enhanced. Forgetting about the amount of the charge, thermionic RF gun is quite suitable to produce such a very short bunch. We have developed an ITC (Independently-Tunabel-Cells) RF gun, which is consisted with two independent cavities in order to manipulate the longitudinal phase space. In addition to expected performance of the ITC RF gun and the bunch compressor, the paper describes the latest version of the lattice design of the isochronous ring and results of tracking simulations as well. Possibility of long wavelength SASE mode and superradiant on the isochronous ring are also discussed. H. Hama, Proc. the 27th Int. Free Electron Laser Conf., Stanford, CA (2005) 1-7. ** T. Tanaka, F. Hinode, M Kawai, A. Miyamoto, K. Shinto, H. Hama, Proc. PAC2005, Knoxville, TN (2005) 3499-3501.

TUPPH028	The Research of FIR-FEL in CAEP	electron, cathode, wiggler, brightness	386
	X. Yang, X. Jin, M. Li, W. Li, Z. Xu CAEP/IAE, Mianyang, Sichuan
	The research of FIR-FEL has been undertaken about 10 years in CAEP and first lasing at center wavelength 115·10^-6 m was observed in March 2005. The facility consists of RF-gun, alpha magnet, L-band SW accelerator, beam transport line, wiggler, optical cavity and measurement system. At present, a high brightness photo cathode RF-gun is commissioning, the cathode material is Cs2Te. This injector will be used in the FIR-FEL project in the second half of this year. In this paper, the design consideration, the system layout, some experimental results are introduced.

TUPPH038	Commissioning of S-band RF GUN and Linac for the Mark-III FEL Facility at Duke University	linac, cathode, electron, emittance	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	emittance, linac, focusing, 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	emittance, electron, diagnostics, booster	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.

TUCAU04	FEL Activities in India	undulator, electron, linac, plasma	496
	S. Krishnagopal, B. Biswas, S. Chouksey, S. K. Gupta, U. Kale, A. Kumar, V. Kumar, S. Lal, P. Mehta, P. Nerpagar, K. K. Pant RRCAT, Indore (M. P.)
	We are building a Compact Ultrafast Terahertz Free-Electron Laser (CUTE- FEL), designed to lase between 50 - 100 microns. It will be driven by a 15 MeV electron beam from a Plane-Wave Transformer linac. The undulator is a 5 cm period, 2.5 m long, PPM planar undulator. We present details of the FEL design and the present status of activities. We also present very preliminary plans for a short-wavelength SASE FEL in India.
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THPPH003	A High Average Power RF-Photoinjector Gun Cavity Developed for the BESSY Soft X-ray FEL	emittance, 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, emittance, 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.

THPPH007	First RF-Measurements at the 3.5-Cell SRF-Photo-Gun Cavity in Rossendorf	cathode, electron, coupling, simulation	567
	A. Arnold, H. Buettig, D. Janssen, U. Lehnert, P. Michel, K. Moeller, P. Murcek, Ch. Schneider, R. Schurig, F. Staufenbiel, J. Teichert, R. Xiang FZR, Dresden T. Kamps, D. Lipka, F. Marhauser BESSY GmbH, Berlin G. Klemz DESY Zeuthen, Zeuthen W.-D. Lehmann IfE, Dresden A. Matheisen, B. van der Horst DESY, Hamburg J. Stephan IKST, Drsden V. Volkov BINP SB RAS, Novosibirsk I. Will MBI, Berlin
	At the Forschungszentrum Rossendorf the development and the setup of the 2nd superconducting radio frequency photo electron injector (SRF-Photo-Gun) is nearly finished. One of the main attention was focussed at the treatment of the cavity. Their RF properties were measured at room temperature. The warm tuning was carried out considering pre-stressing and tuning range of both tuners (half cell and full cells). The adjusted field profiles and pass band frequencies of the four fundamental modes met the requirements. An external Q study of the main coupler yielded to an optimal antenna length and showed very good agreement between simulation and measurement. Furthermore the characteristics of the choke filter and both HOM filters were simulated, measured and tuned at the pi-mode frequency. The preparation (etching and rinsing) and the cold test were successfully done at DESY. The poster presents the setup for the measurements as well as a comparison of the simulated and measured results. Submitted as poster to the 2006 FEL conference

THPPH008	High Peak Current Design of a Superconducting Cavity for a SRF Photoinjector	emittance, 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	cathode, vacuum, acceleration, emittance	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	cathode, electron, emittance, 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, emittance, electron, space-charge	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.

THPPH019	Investigations of Longitudinal Beam Properties at the Photoinjector Test Facility in Zeuthen	booster, electron, photon, dipole	597
	J. R. Roensch, J. Rossbach Uni HH, Hamburg G. Asova, J. W. Baehr, H.-J. Grabosch, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, A. Oppelt, B. Petrosyan, S. Riemann, L. Staykov, F. Stephan DESY Zeuthen, Zeuthen D. Lipka, F. Marhauser, R. Richter BESSY GmbH, Berlin A. P. Onuchin BINP SB RAS, Novosibirsk
	The goal of the Photoinjector Test Facility at DESY in Zeuthen (PITZ) is to test and optimise electron guns for FELs like FLASH at DESY in Hamburg. In 2005 the setup was extended by a booster cavity. In order to measure longitudinal and transverse beam properties in the range between 5 to 40 MeV/c, a viewport after the booster cavity was developed. It contains several radiators. One of them is Silica aerogel used as Cherenkov radiator for the measurement of the longitudinal electron distribution with a streak camera. Design considerations are presented and maybe first measurement results are available. The longitudinal distributions after the booster for different beam parameters are compared to the distributions before the booster.

THPPH023	Tuning, Conditioning, and Dark Current Measurements of a New Gun Cavity at PITZ	cathode, resonance, electron, laser	609
	A. Oppelt, K. Abrahamyan, O. A. Aldrian, G. Asova, J. W. Baehr, G. Dimitrov, H.-J. Grabosch, L. Hakobyan, Y. Ivanisenko, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, V. Miltchev, B. Petrosyan, R. I. Spesyvtsev, L. Staykov, F. Stephan DESY Zeuthen, Zeuthen K. Floettmann, J. H. Han, C. Martens, R. Meyer, F. Tonisch DESY, Hamburg O. Kalekin Humboldt Universität zu Berlin, Berlin F. Marhauser, R. Richter, E. Weihreter BESSY GmbH, Berlin P. Michelato, L. Monaco, D. Sertore INFN/LASA, Segrate (MI) J. R. Roensch Uni HH, Hamburg
	In December 2005, a new gun cavity for the Photo Injector Test Facility at DESY in Zeuthen (PITZ) was tuned at Hamburg with the help of a specially designed tuning device. The tuning processus and its results as well as RF measurements will be presented. Meanwhile, the cavity was installed in the PITZ facility and conditioned. Dark current measurements with different cathodes were undertaken and will be described in the paper. Comparisons to former measurements will be made.

THPPH026	Design of a Two-Stage Laser Pulse Shaping System for FEL Photoinjectors	laser, simulation, controls, insertion	617
	M. B. Danailov, A. A. Demidovich, R. Ivanov ELETTRA, Basovizza, Trieste
	Temporal pulse shaping is one of the most important requirements to photoinjector lasers needed in the majority of FEL projects. The laser pulses commonly requested for excitation of the photocathode are in the UV (around 260 nm) and have flat-top shape of duration in the 5-10 ps range. More complex pulse shapes like "water-bags" and ramps have also been proposed recently, indicating that the pulse shaping scheme must offer flexibility in generating different shapes. In this paper we present an approach which combines the two main pulse shaping techniques, namely acousto -optic dispersive filter (DAZZLER) and Fourier-based 4-f system. The DAZZLER is inserted between the seed mode-locked oscillator and the amplifier and is used for preliminary shaping in the infrared, while the final pulse shape and duration are determined by a 4-f system incorporating deformable mirror positioned after the harmonic conversion to UV. The paper provides simulations and experimental results on designed and measured pulses of both flat-top and asymmetric (ramp) type, comparing solutions based on different distribution of amplitude and phase shaping between the two parts of the shaping setup.

THPPH028	Further Studies in the FERMI@ELETTRA Photoninjector Optimization	emittance, laser, 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, diagnostics, controls, emittance	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.

THPPH034	Laser Pulse Length Dependence of Beam Emittance of Photocathode RF-Gun	laser, emittance, electron, 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	emittance, 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.

THPPH037	Magnetic Field Measurement of the Undulator in KU-FEL	undulator, electron, laser, radiation	660
	M. Nakano, T. Kii, K. Masuda, H. Ohgaki, N. Okawachi, T. Yamazaki, K. Yoshikawa, H. Zen Kyoto IAE, Kyoto
	We have constructed an infrared FEL facility for advanced energy researches. In the last FEL conference, numerical studies on the undulator in KU-FEL by optimizing both for electron beam and for the optical cavity have been presented. On the other hand, since the undulator had been used in FELI, demagnetization has been anticipated. So we have measured the magnetic field of the undulator. In this conference, we will show the FEL gain and the spectrum of spontaneous emission by using the measurement data. T. Fukui, et al., Proc. of the 2005 FEL conference (2005) 195-198. ** E. Nishimura, et al., Nucl. Instr. and Methods, A341 (1994) 39-42.

THPPH038	Production of Electron Beam with Constant Energy by Controlling Input Power into a Thermionic RF Gun	cathode, electron, beam-loading, simulation	664
	N. Okawachi, T. Kii, K. Masuda, M. Nakano, H. Ohgaki, T. Yamazaki, K. Yoshikawa, H. Zen Kyoto IAE, Kyoto
	We have studied on performance of a thermionic RF gun. Though a thermionic RF gun is a compact and economical electron gun, a backbombardment effect makes it difficult to produce electron beam with constant energy. The backbombardment effect depends on cavity voltage of the RF gun (Vc) and cathode current density (Jc). We tried to keep beam energy constant in macro pulse duration by feeding modulated RF power in experiment. We have succeeded to produce a 4 μs macro pulse electron beam. We also tried to perform transient analysis with equivalent circuit including the time evolution of beam loading depending on the Vc and Jc, By using this analysis we have succeeded to reproduce the measured time evolution of electron beam energy and the pulse shape of reflected RF power in case a constant RF power was fed and a modulated RF power was fed. Moreover we found the condition in which we could produce a 6 μs macro pulse electron beam. In this conference we will discuss the comparison between the experimental results and the calculation results.

THPPH039	Experimental Study on Effect of Energy Distribution on Transverse Phase Space Tomography	electron, emittance, simulation, 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, emittance, electron, 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.

THPPH045	Electro-Optic Sampling Method Using High DC Voltage Applying Setup	electron, laser, simulation, monitoring	692
	Y. W. Parc, J. Y. Huang, C. Kim, I. S. Ko, J. H. Park, S. J. Park PAL, Pohang, Kyungbuk X. Dao TUB, Beijing
	A RF photo-cathode (RF PC) gun with 1.6 cell cavity is installed at GTS(Gun Test Stand) being built at the Pohang Accelerator Laboratory (PAL). The short, intense, and low emittance electron beams are produced by the RF PC gun. For the successful construction of PAL-XFEL, the timing jitter and bunch length of the beam at the exit of the gun should be measured accurately. EOS (Electro-Optic Sampling) is a very promising method to measure the jitter without any interference with the electron beam. The spatially resolved method will be used in this experiment, which is a single shot measurement using cooled CCD carmera due to very low energy. Before the measurement with the beam at the exit of the gun, the calibration experiment is done with DC high voltage applying setup with 1mm thick ZnTe crystal. The broadening of our laser pulse by the ZnTe crystal is measured with auto-correlation method to know the resolution limit in this experiment and to do data analysis properly. In this presentation, the result of calibration experiment will be presented with a description of the experiment in detail.

THPPH046	Preliminary Measurement of Emittance Evolution Using Emittance Meter at the PAL	emittance, laser, 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.

THPPH050	Beat-Wave Laser-Driven Photoinjector for Superradiance Free-Electron Laser	electron, laser, beat-wave, radiation	699
	Y.-C. Huang, H.-L. Chang, A.-C. Chiang NTHU, Hsinchu
	Electron bunching plays a crucial role in a radiative emission process. Every free-electron laser (FEL) more or less relies on periodic bunching of electrons to build up radiation power. In this paper, we present our study on the generation and acceleration of periodically bunched electrons in a photo-injector. The idea is to use a laser beat wave to induce a density modulated photocurrent from a photocathode, which is subsequently accelerated to a relativistic speed. The electron micro-bunches in the density modulated current repeat at the laser beat frequency. Our computer simulations using the ASTRA* code show remarkable modulation contrast in > 50 A output current of a 4 MeV RF photocathode gun and a 20 MeV photocathode accelerator. With slight modifications to a conventional photocathode-gun driver laser, a UV beat-wave laser with a variable beat frequency can be implemented by combining two chirped laser pulses with a variable time delay. We will report our experimental progress toward realizing such a new technique in a compact superradiance Smith-Purcell FEL at THz frequencies. * K. Floettmann, ASTRA User Manual, http://www.desy.de/mpyflo/Astra\_dokumentation

THPPH053	3-D Laser Pulse Shaping for Photoinjector Drive Lasers	laser, simulation, emittance, electron	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.

THPPH063	In-Situ Cleaning of Metal Photo-Cathodes in RF Guns	cathode, ion, laser, electron	732
	J. F. Schmerge, J. Castro, J. E. Clendenin, E. R. Colby, D. Dowell, S. M. Gierman, H. Loos, M. Nalls, W. E. White SLAC, Menlo Park, California
	Cu cathodes installed in rf guns typically exhibit much lower quantum efficiency than the theoretical limit. Experimenters often use some sort of in situ technique to "clean" the cathode to improve the QE. The most common technique is laser cleaning where the laser is focused to a small spot and the laser is scanned across the cathode. However, this can also damage the cathode since the laser is operated near the damage threshold and the QE degrades over days and must be cleaned regularly. Alternatively Hydrogen ion beams can be used to clean the cathode and improve the QE but this cleans only the area exposed to the ion beam. In this paper we measure the QE and the dark current emitted from a cathode before and after exposing the gun to a hydrogen plasma created with an rf discharge. With this technique the entire surface of the gun is cleaned simultaneously with no apparent detrimental effects.

THCAU02	Low Emittance Injector at SCSS	emittance, electron, 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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THCAU03	Operational Experience with the Emittance-Meter at SPARC	emittance, cathode, laser, 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, emittance, vacuum	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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