Study on the compensation of linear sum resonance for further beam power ramp-up in J-PARC RCS

Kojima, Kunihiro ; Harada, Hiroyuki  ; Chimura, Motoki   ; Nagayama, Shota*; Saha, P. K.   

A detailed study on the random resonance was conducted to ensure sufficient tunability in the 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC). The progressive improvement in beam intensity, aiming for an output beam power of 1.5 MW, inevitably excites the effect of the structure resonance and requires the operating point to be shifted higher. Employing a low-intensity beam, the excitation of the sum linear resonance locating just above the current operating point is revealed. The linear sum resonance was confirmed to be compensated by making local bumps in the arc section by using the steering magnets. Based on the resonance driving term, the main source of the imperfection field is identified as the leakage field from extraction magnets.