Abstract
In high-intensity proton synchrotrons, controlling beam loss during machine operation is crucial to prevent radiation damage. Uncontrolled beam loss poses a significant challenge in achieving higher beam intensity and power in these synchrotrons. The beam collimation system plays a vital role in removing halo particles and localizing beam loss, serving as a critical tool for controlling uncontrolled beam loss in high-intensity proton accelerators. To address the issue of uncontrolled beam loss, a two-stage transverse collimation system was designed at the rapid cycling synchrotron (RCS) of China Spallation Neutron Source (CSNS). However, during the beam commissioning, it was found that the collimation efficiency was compromised due to the small ratio of the physical acceptance to the collimator acceptance and insufficient phase advances between the primary and secondary collimators. To address this issue, the designed two-stage collimator was modified to a one-stage collimator. Through optimization of the collimation system, the beam loss was effectively localized within the collimator area. As a result, CSNS achieved the design power of 100 kW with minimal uncontrolled beam loss.