Scattering effect in proton beam windows at spallation targets

摘要

Proton beam window (PBW) is a boundary wall between a high vacuum area in theproton beam line and the helium atmosphere in a helium vessel at a high beampower target. The thermal and mechanical problems of the PBW have been studiedin other spallation neutron sources; however, the scattering effect in PBW isseldom reported in literature but it may pose serious problems for the targetdesign if not well treated. This paper will report the simulation studies ofthe scattering effect in PBW. Different materials and different structures ofPBW are discussed. Taking CSNS as an example, a thin single-layer aluminumalloy PBW with edge cooling has been chosen for CSNS-I and CSNS-II, and asandwiched aluminum alloy PBW has been chosen for CSNS-III. Simulations resultsof the scattering effect in the presence of beam uniformization at target byusing non-linear magnets at the different CSNS PBWs are presented. Thesimulations show that the scattering effect at PBW is very important in thebeam loss and the beam distribution at the target.