Scattering effect in proton beam windows at spallation targets

The proton beam window(PBW) is a boundary wall between the high vacuum area in the proton beam line and the helium atmosphere in the helium vessel at a high beam power target. The thermal and mechanical problems of PBW have been studied in foreign spallation neutron sources; however, the scattering effect in PBW is seldom reported which poses serious problems to the target design if not well treated. This paper will report the simulation studies of the scattering effect in PBW. Different materials and different structures of PBW are discussed. Taking China Spallation Neutron Source(CSNS) as an example, a thin single-layered aluminum alloy PBW with edge cooling has been chosen for CSNS-Ⅰ and CSNS-Ⅱ, and a sandwiched aluminum alloy PBW has been chosen for CSNS-Ⅲ. The simulations results o