The Beam Loss Monitoring Research On Injector-Ⅱ Of ADS

The beam loss monitoring system(BLM system) is designed for measuring beam loss around accelerator. The BLM system is widely used in today’s accelerators as a beam diagnostic and machine protection tool.The injector-Ⅱ is one of the injector of high intensity accelerator in Accelerator Driven subcritical System in China, which is a totally super-conducting accelerator, the design beam energy is 10 MeV and current is 10 mA. This thesis is focused on the basic issue on BLM system of injector- Ⅱ from three parts: simulation of the second radiation field, study of the pre-selected detectors and test of online monitoring system. Firstly, the radiation field of injector- Ⅱ was simulated with Monte Carlo code: FLUKA, obtained the neutron, gamma distribution caused by different beam loss circumstance, and gives out the reasonable installation position of detector. Secondly, based on the extensive survey and characteristics of radiation field, the pCVD diamond detector, scintillator based neutron detector and proportional chamber were employed, and according to the basic performance of those detectors, the feasibility of those detectors as beam loss detector were investigated. According to the test results, the E6876 proportional counter tube could play a minor role in beam loss monitoring for its high sensitive, fast response time and good signal-to-noise ratio. Aim at EJ-410 and EJ-420 scintillator based neutron detector, the amplitude of neutron signal is much higher than gamma’s, their good discrimination of neutron/gamma and fast response make them be the most possible beam loss detector. The CVD diamond detector could detect both neutron and gamma, it’s a potential in-cryomodule detector and may play a important role in beam loss monitoring at high energy segment. In addition, on account of the data acquisition system, the pCVD diamond detector was tested more detailed, which contains the Pu-Be neutron source, the injector-Ⅱ and HIRFL-128 experime nt a l terminal. Those results indicate that the counts of detector has a linear response to the dose rate, which makes it possible for beam loss monitoring.In conclusion, according to the results of radiation field simulation, the background radiation field caused by field emission, activation and beam dump is far above the one caused by beam loss, which makes it impossib le for beam loss monitor ing at injector-Ⅱ in present situation. Once the construction of accelerator is completed in the future, the detectors composed by pCVD diamond detector, scintillator based neutron detector and proportional counter tube could play an important role in beam loss monitoring.