Dynamic correction of extraction beam displacement by field ringing of extraction pulsed kicker magnets in the J-PARC 3-GeV RCS

Harada, Hiroyuki  ; Saha, P. K.   ; Tamura, Fumihiko   ; Meigo, Shinichiro   ; Hotchi, Hideaki  

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 2 bunches by using 8 pulsed kicker and 3 septum magnets with 25Hz repetition. The extracted beam is simultaneously delivered to the Material and Life science Facility (MLF) as well as the 50-GeV synchrotron. The kicker magnets have the ringing of flat-top field and the ringing causes the position displacement. The displacement is big issue because it directly causes an emittance growth of the extracted beam. In the beam tuning, we performed a timing scan of each kicker magnet by using a shorter pulse beam and understood the characteristics of ringing field. We then carefully optimized timing of each kicker for the ringing cancellation. The displacement was reduced to be less than 1mm as compared to that of 15mm with no ringing correction. The present correction method and experimental results will be reported.