The Simulation Study Of The Neutron Guide For Neutron Scattering Project Of China Advanced Research Reactor

China Advanced Research Reactor (CARR) Neutron Guide(NG) system, including the divergent neutron guide Cold Neutron Guide D (CNGD) and other two guides, is one of the most important parts in Neutron Scattering Project at China Advanced Research Reactor. At present, we plan to install two new facilities which will be fabricated by China Institute of Atomic Energy and China Academy of Science on the divergent guide CNGD.Our NG system takes advantage of supermirror being used to increase the neutron flux. Compared with the natural Ni and ⁵⁸Ni materials, the supermirror can significantly increase the flux of the neutron beam. However, we have still done many works to find the suitable parameters of the guide system to make sure that the curved guide system can eliminate the fast neutrons and Y -rays, and the neutron beams can be collimated and distributed symmetrically at the exit of the straight guide system. The key point of this thesis is optimizing the parameters of the NG system.In order to calculate the parameters of the guide system, we first investigate the properties of the neutron guide system using the Straight-Curve neutron guide theory, then the Monte Carlo program VITESS has been used to simulate the neutron beam. We have acquired dozens of groups of results. Considering the symmetrical demand and the demand of the divergent angle at the exit of the guide, we find the suitable parameters of the NG system.Meanwhile, a new open calculation program—Neutron Guide Position Simulation (NGPS) has been set up to calculate the NG distribution including the divergent guide. Not only can the program calculate all of the guide elements position data, but also can provide the guide information of any fixed position in the hall if there occurred guide element.At last, we calculate several groups of NG parameters by NGPS in order to get the guide system distribution coordinates. Comparing all the above demands, we pick up the best parameters as the CARR neutron guide system's reference parameters.