A novel method for monitoring proton beam spot using back-streaming secondary neutrons from the target

The proton beam power of the high-power spallation neutron source is generally from 100 kW to several MW. The distribution of beam power density on the target is critical for the stable operation of the high-power spallation target. We propose a novel beam monitoring method, namely a high-power proton beam spot imaging on a target based on the principle of pinhole imaging using the back-streaming secondary neutrons from the spallation target. The fast indirect imaging for the beam spot can be achieved at a distance of tens of meters away from the target. The beam monitoring method can flexibly adjust the pinhole size and measurement distance to control the flux intensity of secondary neutrons according to the demands of the detection system. The detection system is away from the high-radiation target area. From simulations, the beam spot of the incident proton can be restored by using the point response function and image of secondary neutrons with a resolution of about 2 mm.