Maesaka, H.

Paper	Title	Page
MOPC010	Injector System for X-ray FEL at SPring-8	85
	H. Hanaki, T. Asaka, H. Ego, H. Kimura, T. Kobayashi, S. Suzuki JASRI/SPring-8, Hyogo-ken T. Hara, A. Higashiya, T. Inagaki, N. Kumagai, H. Maesaka, Y. Otake, T. Shintake, H. Tanaka, K. Togawa RIKEN/SPring-8, Hyogo
	The SPring-8 X-FEL based on the SASE process has been developed to generate X-rays of 0.1 nm by the combination of an 8 GeV high gradient linac (400 m) and a mini-gap undulator of in-vacuum type (90 m). The design goals of the slice beam emittance and peak current at the end of the linac are 1 π mm mrad and 3 kA, respectively. The injector of the linac generates an electron beam of 1 nC, accelerates it up to 30 MeV, and compresses its bunch length down to 20 ps step by step. The injector has been designed on the basis of the SCSS test accelerator. We adopted the following keys to toward the goals: A 500 kV thermionic gun (CeB6) without a control grid ejecting a beam holding the low rms emittance of 1.1 π mm mrad, a beam deflector downstream gating the beam to form a bunch of a 1 ns length, multi-stage RF structures (238, 476 and 1428 MHz) bunching and accelerating the beam gradually to maintain the initial emittance, and extra RF cavities of 1428 and 5712 MHz linearizing the energy chirp of the beam bunch to achieve the bunch compression resulting the required peak current.
TUPC075	Development Status of a Beam Diagnostic System with a Spatial Resolution of Ten Micron-meters for XFEL	1224
	Y. Otake RIKEN Spring-8 Harima, Hyogo H. Ego, H. Tomizawa, K. Yanagida JASRI/SPring-8, Hyogo-ken A. Higashiya, S. I. Inoue, H. Maesaka, T. Shintake, M. Yabashi RIKEN/SPring-8, Hyogo
	Aroud 10 micron-meter stability of an electron beam is required along the undulator section of XFEL to stably generate an X ray laser, and comparable resolution is also required for beam position and size measurements. At SPring-8, the construction of an 8 GeV linac with undulators is now in progress to realize the X ray laser driven by such highly qualified electron beams. To obtain these beams, measurements of the spatial and temporal beam structures are very important. We are developing a beam diagnostic system with a measurement resolution of less than 10 micron-meters. The system comprises a cavity type beam position monitor, an optical transition radiation profile monitor, a beam current monitor, an rf beam deflector to diagnose femto-second order temporal structure, and beam slits to shape appropriately beam spatial structure. The arrangement of these instruments were decided by requirements of the beam position and size measurements based on beam optics design. This paper describes the development status of the beam diagnostic system. The test results and design of the instruments showed sufficient performance to realize the above mentioned measurement resolution.
TUPC143	Precise RF Control System of the SCSS Test Accelerator	1404
	H. Maesaka, T. Fukui, N. Hosoda, T. Inagaki, T. Ohshima, Y. Otake, H. Tanaka RIKEN/SPring-8, Hyogo T. Hasegawa, S. Takahashi, S. Tanaka JASRI/SPring-8, Hyogo-ken M. K. Kitamura NDS, OSAKA
	We present the development and performance of the low level rf control system of SCSS test accelerator (VUV-FEL facility). The FEL radiation in the wavelength region of 50-60 nm reached saturation in fall 2007. Since then, the FEL intensity fluctuation has been suppressed within 10%. This performance was achieved by stabilizing the rf phase and amplitude of the accelerator. For example, the rf phase stability of the 238 MHz cavity is achieved to be 0.03 degree rms corresponding to 350 fs. Those of other cavities such as C-band (5712MHz) accelerator are also obtained to be several 100 fs. To control the rf phase and amplitude precisely, we have developed an IQ modulator / demodulator system. To treat the baseband signal of the system, we have also developed VME high speed DAC / ADC boards. The phase skew of the IQ system is ± 1.0 degree without correction and ± 0.1 degree after correction. To suppress the slow drift of rf components, we applied a PID feedback control loop to the rf source and cavity system. We also improved temperature stabilization for the acceleration structures.
WEOAM01	Operation Status of the SCSS Test Accelerator: Continuous Saturation of SASE FEL at the Wavelength Range from ~50 to 60 nanometers	1944
	H. Tanaka, T. Fukui, T. Hara, A. Higashiya, N. Hosoda, T. Inagaki, S. I. Inoue, T. Ishikawa, H. Kitamura, M. K. Kitamura, H. Maesaka, M. Nagasono, T. Ohshima, Y. Otake, T. Sakurai, T. Shintake, K. Shirasawa, T. Tanaka, K. Togawa, M. Yabashi RIKEN/SPring-8, Hyogo T. Asaka, T. Hasegawa, H. Ohashi, S. Takahashi, S. Tanaka JASRI/SPring-8, Hyogo-ken T. Tanikawa RIKEN Spring-8 Harima, Hyogo
	The SPring-8 compact SASE source (SCSS) test accelerator for XFEL/SPring-8 was constructed in 2005. The first lasing at 49 nm, though not reached saturation, was observed with the 250-MeV electron beam in June 2006. Towards the saturation, we started stabilizing the RF system in the injector section, which dramatically stabilized the lasing condition. The stable operation enables us to tune each of the machine parameter precisely by using the lasing response. The second undulator, which did not sufficiently contribute to the first lasing because of large multipole field errors, was replaced by new one. These improvements led us to the successful observation of SASE saturation at the wavelength ranging from ~50 to 60 nm in September 2007. A pulse-energy of 30 uJ is routinely obtained at 60 nm. Analysis of the obtained SASE saturation data with a 3D-FEL simulation code, SIMPLEX, suggests that the electron beam emittance is almost unchanged through the bunch compression process. The stable and intense EUV SASE FEL has been offered for user experiments since October 2007. The achieved electron beam performance, lasing property as well as the latest analysis result will be presented.
	Slides