Author: Tanaka, T.
Paper Title Page
THPC142 Burst Pulse Superimposed Electron Beam Acceleration in LEBRA FEL Linac 3218
  • T. Tanaka, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, N. Sato
    LEBRA, Funabashi, Japan
  • S. Aizawa, Y. Arisumi, K. Shinohara
    Nihon Koshuha Co. Ltd, Yokohama, Japan
  • I. Sato
    Nihon University, Advanced Research Institute for the Sciences and Humanities, Funabashi, Japan
  The electron beam for free electron laser (FEL) at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University had been extracted from a conventional DC triode electron gun system. In conjunction with the renewal of the gun high voltage terminal a Kentech high-speed grid pulser was installed in addition to the conventional grid pulser. The 89.25MHz sine wave frequency-divided from the 2856MHz accelerating RF has been applied to the high-speed grid pulser, generating 64 or 128 frequency-divided grid pulses synchronous with the round-trip time in the FEL optical resonator. The high-speed grid pulses have been applied to the EIMAC Y646B cathode simultaneously with the conventional macropulse through the pulse coupling strip-line circuit; the resultant beam has been the short pulse beam superimposed on the macropulse beam. By reducing the macropulse voltage, only the train of the burst beam with 0.6ns width has been extracted. The peak burst beam current roughly 6 times higher than the conventional macropulse beam has been obtained with the Farady cup at the end of the FEL beamline. The FEL lasing experiment with the burst beam is underway.  
THPC032 Current Status of SPring-8 Upgrade Plan 2981
  • T. Watanabe, T. Asaka, H. Dewa, H. Ego, T. Fujita, K. Fukami, M. Masaki, C. Mitsuda, A. Mochihashi, T. Nakamura, H. Ohkuma, Y. Okayasu, Y. Shimosaki, K. Soutome, M. Takao
    JASRI/SPring-8, Hyogo-ken, Japan
  • T. Tanaka
    RIKEN Spring-8 Harima, Hyogo, Japan
  The SPring-8 upgrade plan has been discussed. The main goal is to replace the storage ring in the existing tunnel so that the resulting emittance will get as close to the diffraction limit in hard x-ray region as possible. For 10 keV photons, for instance, the diffraction limit corresponds to the emittance of as small as 10 pm.rad. For the challenging goal, the new ring features a multi-bend lattice with damping wigglers, which presumably enables us to reduce an emittance by two orders of magnitudes or more compared with the current double-bend lattice without damping wigglers. Up to now, a six-bend lattice has been mainly studied, which is supposed to generate a natural emittance of 60–70 pm.rad for 6 GeV. In addition, damping wigglers and coupling control should assist to reduce the emittance even more for approaching the ultimate goal. The major modification requires not only an advanced lattice design via manipulation of non-linear beam dynamics but also extensive technological developments in almost every component such as magnets, monitors, and RF systems. The overall review of the upgrade plan, including some detailed discussions on the critical issues, will be presented.  
TUPC091 Operational Results of the Diamond-based Halo Monitor during Commissioning of SPring-8 XFEL (SACLA) 1218
  • H. Aoyagi
    JASRI/SPring-8, Hyogo-ken, Japan
  • Y. Asano, H. Kitamura, T. Tanaka
    RIKEN/SPring-8, Hyogo, Japan
  Funding: This work is partly supported by Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (c) 21604017.
Measurement of electron beam halo is very important issue for X-ray free electron laser and synchrotron radiation facilities, because the beam halo may cause radiation damage of undulator magnets. Furthermore, it may cause degradation in quality of electron beam, and radio activation of beam ducts and components. In order to prevent these situations, a diamond-based halo monitor (HM) has been developed for the SPring-8 Angstrom Compact free electron LAser (SACLA). We have achieved excellent detection limit of 0.3 fC/pulse for single-shot measurement, which corresponds to the ratio of 10-6 to the beam core. The commissioning of the HM, which was installed at the upstream of 90m undulator, has been carried out, and it has been figured out that the intensity of the beam halo can be measured very nicely since secondary electrons and bremsstrahlung that are emitted in the accelerator components have not been observed. We also describe systematic profile measurements of the beam halo and operational results of the HM during the commissioning of SACLA.