OffSet measurements at Rapid Cycling Synchrotron in China Spallation Neutron Source

The Rapid Cycling Synchrotron(RCS) is the key part of the China Spallation Neutron Source(CSNS) with a repetition rate of 25 Hz. The lattice of the RCS is based on triplet cells with a superperiod of four. Due to the utilization of the trim quadrupoles in June 2021, the Beam Position Monitor(BPM) offsets have been carefully measured, and the beam operation is more stable. In this paper, we will review the preparation of BPM offsets measurements with the virtual accelerator and the experimental results in beam commissioning.