| Many countries focused on the proton accelerators research currently and have promoted a series of research plans concerning high power and high intensity proton accelerators. The Large Hadron Collider in CERN is the highest energy proton accelerator world widely now with the proton energy 7TeV and 14 TeV in the mass center. Another research area is high current proton accelerators, for example, the Ring Cyclotron in PSI, swiss, and SNS in America, both of whose power are beyond 1MW. Those accelerators are mainly utilized on nuclear physics researches, besides, the high intensity proton accelerators could be applied to other areas, such as the nuclear waste transmutation. ADS is the equipment specially designed for nuclear waste disposal with high power. In China’s ADS plan, the designed current is 10 mA, and the operating power is beyond 10 MW. Full superconducting skill is adopted in this plan so that the slow protons could be accelerated by the superconducting accelerator from 2.1 MeV to 1 GeV and above. It is verified that design in this manner is beneficial to achieve high current. Beam loss, one of the mainly restrictions of improvement of the proton accelerator power, could lead to several severe consequences. Firstly, it could cause damage to the radiation materials and further accelerator components dysfunction. Secondly, induced radioactivity in radiated machines would affect the maintaining works. There are two methods to prevent the beam loss, one is optimizing the design to minimize the loss, and another is developing the beam loss monitoring system by observing the radiation field induced by the beam loss to quickly detect the beam loss so that reducing the harms.This paper focused on developing the beam loss monitoring system for C-ADS low energy stage. That the beam loss happens more in the low energy stage and the secondary radiation field caused by the proton loss is relatively weaken requires prime system properties. The radiation field caused by the proton beam loss was analyzed firstly by Monte Carol simulation. Applying software, like SRIM, MCNPX, FLUKA, to simulate the energy spectrum distributions of protons, neutrons and electrons produced by the proton loss. Meanwhile, we also discussed the radiation field that irrelevant with the proton beam, for instance, field emission, multipacting, X-rays emitting by RF source and decay of the activated components, etc. Albeit all those radiation fields are just interferences, they are worth studying for the accelerator protection.Once the radiation distribution and the production of various secondary particles are settled, the particle needed to be detected and related detectors could be determined then. Due to the full superconducting design of the C-ADS, secondary radiation filed in low energy area is very weak, but the superconducting accelerating cavity has no good tolerance to beam loss, which requires the beam loss detector has fast enough responding ability and low-temperature working capacity. Current popular beam loss detectors cannot satisfy that, therefore, three different detectors were chosen in this paper for three different particles. To be specify, they are scraper detector, diamond detector and polyethylene scintillator for electrons, protons and neutrons respectively. Combining the landscape of accelerators, we determined the position and related parameters of each detector, and conducted several property tests.Further, data acquisition system also discussed in this paper. Based on the beam loss monitor systems in HLS-Ⅱ and LHC, we adopted the internet to construct a three level data acquisition system which includes the upper computer, middle system and data collector. Beam parameters are pre-set on this system which empowers the beam loss monitor system dysfunction analysis capability, which is very helpful for the machine diagnosing. Also, this system could render favor to the research of radiation protection. |
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