新型二维位置灵敏中子探测器研究

Neutron scattering, which has been applied in many fields, is of utmost importance for probing the structure and dynamics of condensed matters. With the construction of the China Advanced Research Reactor (CARR), China Mianyang Research Reactor (CMRR) and China Spallation Neutron Source (CSNS), the neutron detectors with large area, high detection efficiency, high position resolution, high time resolution and high n/γ rejection ratio are required. The recent shortage in the supply of He-3 gas for neutron detection and the urgent demands from the neutron scattering devices have caused a large surge in research for a viable replacement. A detector of B-10 coated multi-player MultiWires-Proportional Chamber (mMWPC) will be researched and constructed to meet the demands of neutron scattering experiment devices in construction. The novel neutron detector is consisted of a succession of MWPCs with an anode-wire plane sandwiched by two B-10 coated Flexible Printable Circuit boards (FPC) with perpendicular readout strips coated on each other, which are considered to be the neutron conversion screens and the readout planes at the same time. Because of the good time resolution of MWPC, the detector can benefit the neutron spectrum detection through the time of flight method (TOF). Through the R&D of this kind detector, the key technologies such as the boron coating technology on the FPC, the fixation of the FPC, the signal extraction and so on will be grasped.

中子散射是研究物质结构和动力学特征的有效方法，已广泛应用于众多领域。中国先进研究堆、中国绵阳研究堆以及中国散裂中子源等大型中子科学装置的建造对中子探测器提出了更高要求，如大面积、高效率、高位置分辨、高时间分辨以及高n/γ抑制比等。面临He-3气体严重匮乏的国际形势，取代He-3的中子探测器研制已经十分迫切。为满足国内一大批在建和即将建设的中子散射实验装置的需求，拟研制一台基于涂硼的多层多丝正比室新型中子探测器，每个多丝正比室单元包括一个阳极丝平面以及两侧等间距放置的单面涂硼柔性电路板，两个电路板上刻有相互垂直的读出条，在作为中子转换屏的同时还可以实现中子的二维定位，且具有很好的位置分辨能力。此外，多丝正比室具有很好的时间分辨，非常有利于通过飞行时间法获得中子能谱。通过探测器的研制和性能研究，掌握柔性电路板上的涂硼技术及多层柔性电路板的拉伸与定位、信号的引出等关键技术，力争达到国际先进水平。

面临He-3资源紧缺的国际形势，立足国内中子散射装置的需求，本项目提出了一种基于多层多丝正比室结构的涂硼中子探测器。建立了该结构探测器的Geant4/Garfield++联合模拟平台，实现了从中子入射到信号输出的全物理过程模拟。研制了一台3层中子转换层的探测器样机及配套的位置读出系统，有效面积为100mm × 100mm，10B4C中子转换层厚度为2μm，工作气体为Ar/CO2（90/10），计算热中子探测效率为13%，利用Cf-252裂变中子源测试探测器的位置分辨率为σ = 2.96mm。通过项目研究掌握了探测器结构设计、延迟线读出方法、高压引入、信号引出等关键技术，为今后国内中子散射装置大面积多层多丝正比室涂硼中子探测器的使用奠定了基础。