The proton beam window for China Spallation Neutron Source

Abstract

The proton beam window is one of the key devices for China Spallation Neutron Source (CSNS), which is used to separate the high vacuum from the helium circumstance at the target station, as the interference of the accelerator and the target. The design of the proton beam window is a comprehensive issue, covering the beam scattering, energy deposition, thermal–mechanical analyses, remote maintenance and lifetime estimation. We have proposed a single–double layer structure according to the beam distribution of CSNS, which can decrease the beam scattering and energy deposition when the beam passing through, and fulfill the material properties well simultaneously. The proton beam window is connected to the accelerator and the helium vessel by inflatable seals, which has a leak rate as low as 3.9 × 10−10 Pa m3/s and can maintain the vacuum at accelerator side below 1 × 10−4 Pa level. The lifetime of the window is estimated as seven years based on helium production in the condition of the highest current density of 5.85 μA/cm2. The creep elongation is extrapolated only 0.83% in the lifetime, which is small and can be considered safe.