ORBIT simulation, measurement and mitigation of transverse beam instability in the presence of strong space charge in the 3-GeV RCS of J-PARC

Saha, P. K.   ; Shobuda, Yoshihiro   ; Hotchi, Hideaki  ; Harada, Hiroyuki  ; Hayashi, Naoki  ; Tamura, Fumihiko   

The transverse impedance of eight extraction pulse kicker magnets (KM) is extremely strong source of transverse beam instability in the 3-GeV RCS (Rapid Cycling Synchrotron) at J-PARC. To realize the designed 1 MW beam power, collective beam dynamics with including the space charge effect for the coupled bunch instabilities excited by the KM impedance and associated measures were studied by incorporating all realistic time-dependent machine parameters in the ORBIT 3-D particle tracking code. The simulation results were all reproduced by measurements and, as a consequence, an acceleration of 1 MW beam power has been successfully demonstrated. In order to maintain variation of the RCS parameters required for multi-user and stable operation, realistic measures for beam instability mitigation were proposed in this study and also been successfully implemented in reality.