An integrated bremsstrahlung safety shutter and collimator designed for the APS front end operating in the top-up mode

Abstract

The Bremsstrahlung safety shutter is an important device for synchrotron radiation facility personal safety. The APS front ends have double redundant safety shutter assemblies (as per PSAR requirements) that are located about 22.6 m from the source, just upstream of the ratchet wall. These assemblies are needed to guard against an accidental positron beam loss during injection and normal operation, which then can result in high energy Bremsstrahlung radiation being directed down the front end into the First Optics Enclosure (FOE) and the experimental station. In the APS top-up mode of operation, the positron injection will be continued during the normal operation. Therefore, it is necessary to have special Bremsstrahlung shielding to protect the downstream experimental area. There are many ways to do this, but the most economical way is to design a special long Bremsstrahlung collimator in the front-end area. The better the collimation in the front end, the less the shielding material needed in the beamline. The major difficulty in designing the front-end special Bremsstrahlung collimator is the space problem. In the APS, the total length available for the APS ID front end is only about 7.6 m; there is not extra space for additional collimators. To solve this problem, we propose here a novel integrated design that will provide the functions of both a Bremsstrahlung collimator and a safety shutter.