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

Ego, 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:
  1. A 500 kV thermionic gun (CeB6) without a control grid ejecting a beam holding the low rms emittance of 1.1 π mm mrad,
  2. a beam deflector downstream gating the beam to form a bunch of a 1 ns length,
  3. multi-stage RF structures (238, 476 and 1428 MHz) bunching and accelerating the beam gradually to maintain the initial emittance, and
  4. 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.
 
TUPC023 Design of the Transverse C-band Deflecting Structure for Measurement of Bunch Length in X-FEL 1098
 
  • H. Ego
    JASRI/SPring-8, Hyogo-ken
  • Y. Otake
    RIKEN/SPring-8, Hyogo
 
  In SPring-8, the 8 GeV X-FEL with a short length of about 700 m is under construction. An electron beam with a bunch length in duration of less than 200 fs is indispensable for stable and brilliant X-ray radiation. We planned to measure the short bunch length with a transverse RF deflector. A bunch measuring system including the deflector must be located within 15 m of a bunch compressor at a beam energy of 1.45 GeV. To install the system in the restricted space, we need a deflector generating a transverse deflecting voltage over 40 MV. Therefore a new C-band deflecting structure was designed. It is a periodic disk-loaded structure with a racetrack-shaped iris in the center of each disk. The deflecting resonant mode is the HEM11-5π/6 mode of a backward traveling-wave and its transverse shunt impedance is more than 12 MΩ/m. The racetrack-shaped iris serves both as a cell-to-cell coupler and a beam passing hole, prevents rotation of the deflection plane of the HEM11 mode and makes the deflecting mode resonant stably. We represent the details and merits of the C-band structure with the demanded performance in this paper.  
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.  
TUPD028 How to Stably Store Electron Beam in a Synchrotron Radiation Facility from the Point of View of an RF System Design 1485
 
  • Y. Kawashima, H. Ego, Y. Ohashi
    JASRI/SPring-8, Hyogo-ken
  • M. Hara
    RIKEN Spring-8, Hyogo
 
  In any synchrotron radiation facilities, the users wish that electron beams are stably stored without beam abortion for as long as possible. It must be recognized that RF system is a main cause of beam abortions. In order to store beam stably, it is necessary for staffs in charge of RF system to foresee various beam instabilities and to take measures. Before discussing coupled-bunch instability problems, one should understand some trivial issues such as ion trapping and fundamental acceleration frequency modulated by high voltage ripple. The former causes transverse mode instability and the latter shakes stored electron beam longitudinally in RF cavities. In newly designed synchrotron radiation facilities, those issues mentioned above should be suppressed before beam commissioning. As for other issues relating with RF system, we would like to state the importance of a water-cooling system with stable temperature for cavities, and the electric earth problem of low level RF system and high voltage power equipment of a klystron. We describe how we have managed those issues in designing of SPring-8 RF system of the storage ring.