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Monitoring method for neutron flux for a spallation target in an accelerator driven sub-critical system

Chinese Physics C 2016年第7期40卷 129-135页

作者：赵强贺智勇杨磊张雪荧崔文娟陈志强徐瑚珊 Institute of Modern Physics Chinese Academy of Sciences Lanzhou 730000 China University of Chinese Academy of Sciences Beijing 100049 China

In this paper, we study a monitoring method for neutron flux for the spaUation target used in an accelerator driven sub-critical （ADS） system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique, i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 MeV-proton beam with Geant4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber （FC）, by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well.

关键词： accelerator driven sub-critical (ADS) system neutron flux spallation target fission chamber fissioncross section

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Study on collimation and shielding of the back-streaming neutrons at the CSNS target

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Chinese Physics C 2013年第11期37卷 73-78页

作者：敬罕涛唐靖宇杨征 Institute of High Energy Physics Chinese Academy of Sciences

The back-streaming neutrons from the spallation target at CSNS are very intense, and can pose serious damage problems for the devices in the accelerator-target interface region. To tackle the problems, a possible scheme for this region was studied, namely a specially designed optics for the proton beam line produces two beam waists, and two collimators are placed at the two waist positions to maximize the collimation effect of the back-streaming neutrons. Detailed Monte Carlo simulations with the beams in the two different CSNS phases show the effectiveness of the collimation system, and the radiation dose rate decreases largely in the interface section. This can ensure the use of epoxy coils for the last magnets and other devices in the beam transport line with reasonable lifetimes, e.g., thirty years. The design philosophy for such an accelerator-target interface region can also be applicable to other high-power proton beam applications.

关键词： spallation target back-streaming neutrons collimation radiation dose rate epoxy coil

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Measurements and characteristics of Al_(2)O_(3):Cr^(3+) coating for the proton beam imaging system

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Radiation Detection Technology and Methods 2017年第1期1卷 54-60页

作者： Zhirong Zeng Quanzhi Yu Shaohong Wei Bin Zhou Quan Ji Tianjiao Liang Yuanbo Chen Institute of High Energy Physics Chinese Academy of Sciences(CAS)Beijing 100049China Dongguan Neutron Science Center Dongguan 523803China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of ScienceBeijing 100190China

Introduction To set up an online proton beam diagnostic system near the neutron production target of China spallation Neutron Source(CSNS),a luminescence coating sprayed on the target windowand a corresponding optic system were *** the work,the fabrication of Al_(2)O_(3):Cr^(3+) coating was *** on the sprayed samples were performed to analyze the characteristics of the Al_(2)O_(3):Cr^(3+) *** and tests of coating samples Three kinds of powders with different Cr concentrations were used to fabricate the luminescence coating *** flame spraying,plasma spraying and D-gun spraying processes were ***(PL),X-ray diffraction(XRD),scanned electron mirror(SEM)and radioluminescence experiment by 300 MeV deuterium beam were carried out to analyze and characterize the *** The emission spectrum excited by 532-nm laser has two obvious peaks at 692.9 nm and 694.3 *** samples by flame spraying process with the powders obtained from melting method show higher luminescence intensity than the samples by plasma spraying *** is observed that the luminescence intensity has some relationships with the alpha phase in the samples,which is deduced from the XRD and photoluminescence tests results.A lower temperature during the flame spraying process will help to keep more alpha phase in the *** selected four samples show successful fluoresced results in the radioluminescence *** The luminescence intensity of the coating is improved greatly by the studies on the fabrication process and the characteristics of the *** luminescence coating used in beam diagnostics will be fabricated by the confirmed technical *** works will be continued to improve the characteristics of the luminescence light by controlling Cr concentration and annealing in 1200∼2000℃ environment in the future.

关键词： Al_(2)O_(3):Cr^(3+)luminescence coating Beam diagnostics spallation target

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