Applications of programmable trim quadrupoles on beam commissioning for the CSNS RCS

Abstract The design goal of 100 kW beam power of the China Spallation Neutron Source (CSNS) has been successfully achieved in 2020. In order to further increase the beam power more than 100 kW, a total of 16 programmable trim quadrupoles have been installed in the Rapid Cycling Synchrotron (RCS) of CSNS, to achieve accurate adjustment of betatron tunes, better control of twiss parameters, and restoration of lattice super-periodicity. In this paper, we describe the design and several important applications of the trim quadrupoles for beam commissioning in the CSNS RCS. The beam experiments show that the trim quadrupoles play a crucial role in increasing beam power above 100 kW.