A non-intercepting monitoring method for beam position on the target in an accelerator driven system

Abstract

In an accelerator driven sub-critical system (ADS), an intense external neutron source provided by an accelerator coupled to a target is used to drive a sub-critical reactor. To ensure the stable operation of the reactor, it is of crucial importance to locate the beam spot on the target during the operation. In this paper, we have proposed a method for beam position measurement on the target’s beam entrance window. The proposed method is to measure the neutron flux outside the spallation target in the four directions of the east, south, west, and north. Since the neutron flux decreases with the distance between the detector and the beam center, the position of the beam center on the target’s entrance window can be extracted from the measured four neutron fluxes. The simulations based on FLUKA and OpenMC codes have indicated that the x and y positions of the beam center can be extracted from the measured four neutron fluxes. Since the four neutron detectors are fixed inside the reactor core, this method allows for continuous measurement of the beam position.