Shintake, T.

Paper	Title	Page
MOAAU04	First Lasing at SCSS	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	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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MOCAU04	Focal Point Laser-Field as Optical Seeder	242
	T. Shintake RIKEN Spring-8 Harima, Hyogo
	Focusing optical laser into its wavlength size, and crossing the electron beam through the focal point, interaction of electron with laser field becomes non zero, as a result, creates velocity modulation. In contrast with modulation scheme using undulator, this method does not require energy resonance condition to the electron beam, thus works all energy, even with energy chirp. Using it in front of the bunch compressor, with energy chirp, the wavelength can be compressed by large factor with bunch length compression.
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MOPPH046	Seeding the FEL of the SCSS Prototype Accelerator with Harmonics of a Ti:Sa Laser Produced in Gas.	138
	G. Lambert, M. Bougeard, W. Boutu, B. Carré, D. Garzella, M. Labat CEA, Gif-sur-Yvette O. V. Chubar, M.-E. Couprie SOLEIL, Gif-sur-Yvette T. Hara, H. Kitamura, T. Shintake RIKEN Spring-8 Harima, Hyogo
	A particular seeded configuration will be tested in 2006 on the SCSS test facility (SPring-8 Compact Sase Source, Japan). This facility is based on a thermionic cathode electron gun (1 nC), a C-band LINAC (5712 MHz, 35 MV/m) and two in-vacuum undulators (15 mm of period). The maximum electron beam energy is 250 MeV and the SASE emission from visible to 60 nm can be obtained. The external source, obtained by the High order Harmonic Generation (HHG) process, can be tuned from the 3th (260 nm) to the 13th harmonic (60 nm) of a Ti: Sa laser generated in a gas cell. The experiment contains a first chamber, dedicated to harmonic generation and a second one for harmonic beam diagnostics and adaptation of the harmonic waist in the modulator. The tests have been performed in Saclay (15 mJ, 10 Hz, 50 fs). An energy of 2e-6J with a high stability for the 3th harmonic and a good transversal shape with an optimized energy level and a high stability for the 13th harmonic have been obtained at the modulator center place. The performances using PERSEO, GENESIS and SRW will be updated. The chambers will be installed on the SCSS test facility in the beginning of July for seeding tests during summer.
THPPH033	Sub-Pico-Second Trigger System for the SCSS Prototype Accelerator	645
	Y. Otake, H. Maesaka, T. Shintake RIKEN Spring-8 Harima, Hyogo T. Fukui, N. Hosoda, T. Ohata, T. Ohshima JASRI/SPring-8, Hyogo-ken
	At RIKEN, Harima Institute, the project (SCSS) of X-FEL including the 8 GeV linac is in progress. Now, to verify feasibility of X-FEL, the 250 MeV test electron linac is building at SPring-8. A time jitter of the order of ten femto-seconds is required to the timing system of the 8 GeV linac, because of a beam pulse width of several ten femto-seconds. However, realizing this jitter value is very difficult by the present electronics technology. Therefore, we temporarily set a sub-pico-seconds time jitter as a development target, because the beam pulse width of the test linac is several pico-seconds. This jitter value had possibility to be achieved by the present technology. In accordance with the target, we developed a very low noise reference signal source that generates 238 MHz and 5712 MHz RF signals, a master trigger VME module having output pulses synchronized by 238 MHz, and a trigger delay VME module synchronized by 5712 MHz. The time jitter of the delay module is less than 700 fs, and the SSB noise of the 5712 MHz reference signal source is less than -120 dBc at 1 kHz offset. These values are enough for our present requirement.
THPPH043	Stable RF Phase Insensitive to the Modulator Voltage Fluctuation of the C-band Main Linac for SCSS XFEL	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.
THPPH044	Analysis of Inverter Charging Waveform for Ultra Stable SCSS Modulator	688
	J.-S. Oh, T. Inagaki, J.-S. Oh, T. Shintake, K. Shirasawa RIKEN Spring-8 Harima, Hyogo
	The SCSS (SPring-8 Compact SASE Source) XFEL requires ultra stable RF sources. The SCSS uses normal conducting technology for beam acceleration, in which pulse-to-pulse power fluctuation in RF-system dominates beam stability. The SCSS smart modulator uses an inverter charging system. Therefore, the inverter is responsible to RF stability, which means that we need an ultra stable charging power supply. In order to stabilize the charging level, we need a clean and stable feedback signal of the charging voltage. There are not only pulse forming network (PFN) capacitors but also protective series resistors and distributed reactive components of a pulse transformer and a klystron load in the charging path. Therefore, the charging waveform becomes somewhat complicated. In addition, improper conditioning of monitoring signal can easily degrade the charging stability. The understanding of the charging waveform and the proper conditioning of feedback signal is essential to realize such an ultra stable charging performance. This paper shows the detail analysis of the charging waveform of SCSS modulators and the stability dependency on the signal conditioning.
THCAU02	Low Emittance Injector at SCSS	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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