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Title Suppression of Longitudinal Coupled Bunch Instability by Harmonic Cavity in UVSOR Electron Storage Ring
  • A. Mochihashi
    KIT, Eggenstein-Leopoldshafen, Germany
  • M. Fujimoto, K. Hayashi, M. Katoh
    UVSOR, Okazaki, Japan
  • J. H. Hasegawa, M. Hosaka, M. Hosaka, Y. Takashima, Y. Takashima
    Nagoya University, Nagoya, Japan
  • M. Hosaka, Y. Takashima
    Aichi Synchrotron Radiation Center, Aichi, Japan
  • M. Katoh
    Sokendai - Okazaki, Okazaki, Aichi, Japan
Abstract In the UVSOR electron storage ring, which is dedicated for a VUV synchrotron radiation light source, a longitudinal coupled bunch instability (LCBI) is observed in multi-bunch operation. To suppress the LCBI, we routinely operate a third harmonic cavity (HCV) in a passive mode. By properly tuning HCV, the instability is almost completely suppressed. Because of the lower beam energy (750 MeV) and brilliant beam emittance (17.5 nm-rad), the Touschek effect becomes severe in the UVSOR. To guarantee enough beam lifetime, we also apply HCV for lengthening the bunch. The suppression of the instability and increasing the beam lifetime are crucial benefits by HCV for the UVSOR. However, not only the origin of the LCBI but also the Landau damping effect by HCV has not been understood systematically yet. We have noticed that one of the HOMs at HCV itself could cause the LCBI and observed the behavior of the instability, which strongly depends on the beam current. From the experiment we have discussed the cause of the instability with the HOM theory. We have also tried to observe synchrotron tune spread and discussed a competition between the Landau damping and the instability growth.
Footnotes & References Present affiliation of the first auther : Karlsruhe Institute of Technology
Paper download THPAK031.PDF [0.321 MB / 3 pages]
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Conference IPAC2018, Vancouver, BC, Canada
Series International Particle Accelerator Conference (9th)
Proceedings Link to full IPAC2018 Proccedings
Session MC5 Poster Session
Date 03-May-18   09:00–12:00
Main Classification 05 Beam Dynamics and EM Fields
Sub Classification D04 Beam Coupling Impedance - Theory, Simulations, Measurements, Code Developments
Keywords damping, synchrotron, storage-ring, HOM, cavity
Publisher JACoW Publishing, Geneva, Switzerland
Editors Shane Koscielniak (TRIUMF, Vancouver, BC, Canada); Todd Satogata (JLab, Newport News, VA, USA); Volker RW Schaa (GSI, Darmstadt, Germany); Jana Thomson (TRIUMF, Vancouver, BC, Canada)
ISBN 978-3-95450-184-7
Published June 2018
Copyright © 2018 by JACoW, Geneva, Switzerland     CC-BY Creative Commons License
cc Creative Commons Attribution 3.0