Monitoring method of beam on target for accelerator driven sub-critical system

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 continuously produce very intense neutrons, it is of crucial importance to exactly locate the beam spot on the target during the operation. In this paper, we have proposed two methods for monitoring the location of beam center on target. The first method is to measure the spallation neutrons leaking from the spallation target in the four directions of the east, south, west, and north. The simulations based on GEANT4 code have indicated that the spallation neutron flux can be used to estimate the deviation distance and azimuthal angle of the beam center. The second method is to measure the target temperature inside the target container with thermocouples in the directions of the east, south, west, and north. The simulations based on the heat transfer modeling have indicated that if the beam center deviates far from the coordinate origin to a direction, such as east, the thermocouple’s temperature in the east will rise. Thus, the temperature measurement inside the target container can be used to protect the target against abnormal irradiation when the accelerator’s beam deviates far from the target center, by initiating a warning or a trip if safe temperature limit is exceeded.