PSI, Villigen
In March 2010 one of the most exposed collimators of the 590 MeV proton beam line at PSI, was visu-ally inspected after 20 years of operation without failure. It is made out of OFHC copper and cooled by water tubes. At currents of 2.2 mA, the temperature inside the collimator is ~ 350 C. From the total beam charge of 120 Ah, ~15 % are absorbed. The main motivation for the inspection was to investigate the present condition of the collimator after the long exposure in a high intensity proton beam. According to MARS15 the inner parts have seen 35 DPA. For the inspection, the collimator was removed remotely from the beam line by a shielded exchange flask and transferred to the hot cell. In order to enter the collimator opening and examine the inner structure without any contact or damage, a special tool was built, using the principle of a periscope. By moving and rotation the tool with the power manipulator, sharp pictures of the inner surface were taken with a high resolution reflex camera, operated remotely. Because of the high radiation (> 50 Sv/h in 0.2 m) camera and electronics were shielded. After the inspection, the collimator was built in to the beam line again.
PSI, Villigen
PSI is gradually upgrading the 590 MeV proton beam intensity from the present 2.2 mA towards 3 mA, which poses a significant challenge to the reliable operation of the accelerator facility. Of particular concern is the collimator system which is exposed to the dispersed beam from a muon production target. It shapes an optimal beam profile for low-loss beam transport to the neutron spallation source SINQ. The collimator system absorbs slightly more than 10 % of the proton beam power and the maximum temperature of the collimator system exceeds 350 C at 2.2 mA, which is close to the failure point. In this paper, we present a new collimator system design which could withstand the proton beam intensity of 3 mA, while fulfilling the intended functionalities. Advanced multi-physics simulation technology is used for the geometric and material optimizations, to achieve the lowest possible actual to yield stress ratio at 3 mA. A sensitivity study is performed on the correlation between the beam misalignments and the reliability of the key accelerator components in the proton downstream region. Also reported are the possible proton irradiation effects on the mechanical failure criteria.
