DYNAMIC CORRECTION OF EXTRACTION BEAM DISPLACEMENT BY FIELD RINGING OF EXTRACTION PULSED KICKER MAGNETS IN THE J-PARC 3-GEV RCS

The 3-GeV rapid cycling synchrotron (RCS) of J-PARC is designed for a high-intensity output beam power of 1MW. The RCS is extracted two bunches by using eight pulsed kicker and three DC septum magnets with 25Hz repetition. The extracted beam is simultaneously delivered to the material and life science experimental facility (MLF) as well as the 50-GeV main ring synchrotron (MR). The kicker magnets have the ringing of flat-top field and the ringing causes the position displacement. The displacement is big issue because it causes an emittance growth of the extracted beam directly. In the beam tuning, we performed a timing scan of each kicker magnet by using a shorter pulse beam in order to understand the characteristics of ringing field. We then carefully optimized the trigger timings of each kicker for the ringing compensation. We have successfully compensated the extracted beam displacements to (min., max.) = ( 1.1 mm, +0.6 mm) as compared to ( 14 mm, +10 mm) with no ringing compensation. The procedure for ringing compensation and experimental results are reported in this paper.