Space Charge Effects in the Kek-booster Synchrotron

The KEK-PS Booster is a 40to 500-MeV proton synchrotron, which is the injector of the KEK 12 GeV Proton synchrotron, and also delivers a beam to the Booster Synchrotron Utilization Facility (BSF). It is a compact alternating-gradient synchrotron operated at fixed tunes. The repetition rate is 20Hz and the synchrotron magnets are excited by a resonance circuit. The linac beam is injected by charge exchange injection and is adiabatically captured in an RF bucket. A bunch is formed in 600μs and the bunching factor becomes ~0.3. A transverse beam blow-up at the early stage of acceleration has been observed [1]. Since the Booster synchrotron was designed for H+ multi-turn injection, it has apertures of 272 π mm mrad and 49 π mm mrad in the horizontal and vertical planes, respectively [2]. This vertical emittance growth becomes crucial as the beam intensity increases. Since the acceleration period is rather short, we chose the BEAMSCOPE method [3], which can measure a beam profile in 100μs. It is difficult to use a wire scanner and other methods for a quick measurement. In order to measure the beam profile exactly, a precise calibration was performed [1].