• T. Obina, J.W. Flanagan, T. Honda, T.M. Mitsuhashi, M. Tadano, M. Tobiyama
  KEK, Ibaraki
• W.X. Cheng, J.D. Fox
  SLAC, Menlo Park, California
• D. Teytelman
  Dimtel, San Jose

A bunch-by-bunch feedback system has been developed to suppress longitudinal coupled-bunch instabilities at the KEK-PF. A generalpurpose signal processor, called iGp, has been developed by a collaboration among KEK, SLAC and INFN-LNF. A longitudinal kicker based on the DAΦNE-type over-damped cavity was designed and installed in the ring. The whole feedback loop was closed at the end of June 2007. The longitudinal dipole-mode instabilities are successfully suppressed up to 430 mA. The performance and the details of the system will be presented in this paper.

• M. Tobiyama, J.W. Flanagan, T. Obina, M. Tadano
  KEK, Tsukuba

Button electrodes with good time response are essential for the bunch-by-bunch feedback / diagnostic systems needed for future short-bunch-spacing accelerators, such as energy recovery linacs (ERL) or a super B-factory. The impedance matching and time-domain response of electrodes, particularly around the vacuum seal, have been studied using 3-D electromagnetic codes (HFSS, MAFIA and GdfidL). Several candidates have been fabricated to examine the tolerance for mechanical pressures and heat stress due to the welding process. The real beam response from a short bunch has also been studied using a test-beam line at the KEK-PF injector beam transport section.