  The rapid cycling synchrotron (RCS) of the China Spallation Neutron Source
(CSNS) is a high intensity proton ring with beam power of 100 kW. In order to
control the residual activation to meet the requirements of hands-on
maintenance, a two-stage collimation system has been designed for the RCS. The
collimation system consists of one primary collimator made of thin metal to
scatter the beam and four secondary collimators as absorbers. Thermal analysis
is an important aspect in evaluating the reliability of the collimation system.
The calculation of the temperature distribution and thermal stress of the
primary collimator with different materials is carried out by using ANSYS code.
In order to control the temperature rise and thermal stress of the primary
collimator to a reasonable level, an air cooling structure is intended to be
used. The mechanical design of the cooling structure is presented, and the
cooling effciency with different chin numbers and wind velocity is also
analyzed. Finally, the fatigue lifetime of the collimator under thermal shocks
is estimated.
