160 kW beam commissioning for the Rapid Cycling Synchrotron of the China Spallation Neutron Source

Abstract For the China Spallation Neutron Source (CSNS), the rapid cycling synchrotron (RCS) accumulates and accelerates the injection beam to the design energy of 1.6 GeV and then extracts the high energy beam to the target. In this paper, the 160 kW beam power commissioning for the CSNS RCS has been comprehensively studied, including: increase in the pulse width of the injection beam to optimize the transverse painting, commissioning of the two dual harmonic radio frequency (RF) cavities, optimization of the transverse and momentum collimators, longitudinal dynamic optimization, beam instability suppression, global closed orbit correction, local closed orbit correction, optimization of the RCS occasional large beam loss, optimization of the extraction mode and extraction occasional large beam loss, and so on. In order to meet the requirements of beam power increase and stable operation of the accelerator, the RCS beam losses from different sources are studied and optimized. With the aid of weekly radiation dose measurement, the hot spots of the RCS are studied in depth to explore the causes.