【作者】 刘涛；

【导师】 周建斌；

【作者基本信息】 成都理工大学 ， 核科学与技术， 2024， 硕士

【摘要】 随着国家经济的不断发展,人们越来越注重对环境放射性的测量、监测与评估,尤其是对低浓度α、β射线的测量。除了天然放射性核素外,核工业系统和放射性产品的生产、加工与使用部门是环境中α、β射线的主要来源。α、β射线强大的电离能力会对人体形成内照射,危害人的身体健康。因此,低浓度α、β射线的有效监测对于保障人民生命健康与促进涉核工业的发展具有重要意义。基于国内半导体探测器类型的多通道低本底α、β谱仪研究相对较少的现状,本文设计了一种基于钝化注入平面硅（Passivated Implanted Planar Silicon,PIPS）探测器的四路低本底α、β谱仪。仪器的硬件主要包括电源模块、通信模块、能谱测量模块、气路分配模块和控制模块,测量室采用模块化设计,体积小巧,结构紧凑,便于后期维护与通道拓展。仪器的控制模块与能谱测量模块的电源采用隔离设计,以减小电源之间的干扰,而采用以太网通信实现仪器与上位机之间的高速数据传输,确保软件运行的流畅性。仪器每一个通道均包含一套独立的能谱测量系统,保证通道之间在测量时互不干扰,便于仪器的前期调试与后期维护。在设计气路管道时,使用电磁阀和气压传感器控制测量室的抽气与泄压,使用可编程逻辑控制器（Programmable Logic Controller,PLC）作为控制核心,采集气压的同时协调各个通道电磁阀的通断。上位机测量分析软件主要包括参数设置、数据采集、数据分析以及文件操作等功能。软件的配置文件均保存在初始化（Initialization,INI）文件中,数据文件均存储到Access数据库中,两种文件均可通过不同的方式进行增、删、查、改等操作。在调试仪器参数时,可通过软件实时查看原始脉冲与成形脉冲,能够快速确定仪器的最佳工作参数。在测量样品时,软件可通过调节数字增益参数的方式进行稳谱,提升测量准确度。测试结果表明,四路低本底α、β谱仪可正常测量和区分α射线与β射线。在测量时,测量室内部的绝对气压保持在30 Pa以下。仪器的α射线本底计数率小于1cm^-2·h^-1,β射线本底计数率小于30 cm^-2·h^-1。α计数的重复性最大为0.35%,β计数的重复性最大为0.54%。α射线对β道的串道比最大为0.520%,β射线对α道的串道比最大为0.013%。更多还原

【Abstract】 With the continuous development of the national economy,people are paying more and more attention to the measurement,monitoring,and assessment of environmental radioactivity,especially the measurement of low-concentration alpha and beta radiation.In addition to natural radioactive nuclides,the nuclear industry system and the production,processing,and use of radioactive products are the main sources of alpha and beta radiation in the environment.The strong ionizing ability of alpha and beta radiation can form internal exposure to the human body,endangering people’s health.Therefore,effective monitoring of low-concentration alpha and beta radiation is of great significance for safeguarding people’s life and health and promoting the development of the nuclear-related industry.Based on the current situation of relatively less research on multi-channel low-background alpha and beta spectrometers based on domestic semiconductor detector,this thesis designs a four-channel low-background alpha and beta spectrometer based on passivated implanted planar silicon（PIPS）detector.The hardware of the instrument mainly consists of power supply module,communication module,energy spectrum measurement module,gas path distribution module,and control module.The measurement chamber adopts modular design,which is compact in size and has a compact structure,making it convenient for subsequent maintenance and channel expansion.The power supply of the control module and the energy spectrum measurement module is designed to be isolated to reduce interference between power sources,while Ethernet communication is used to achieve high-speed data transmission between the instrument and the upper computer,ensuring the smooth operation of the software.Each channel of the instrument includes a set of independent energy spectrum measurement systems,ensuring that the channels do not interfere with each other during measurement,which is convenient for the preliminary debugging and subsequent maintenance of the instrument.When designing the gas pipeline,electromagnetic valves and pressure sensors are used to control the evacuation and relief pressure of the measurement chamber,and a programmable logic controller（PLC）is used as the control core to collect pressure while coordinating the opening and closing of the electromagnetic valves of each channel.The upper computer measurement and analysis software mainly includes functions such as parameter setting,data acquisition,data analysis,and file operations.The configuration files of the software are all saved in Initialization（INI）files,and data files are all stored in Access databases,both of which can be operated by adding,deleting,querying,and modifying through different methods.When debugging the instrument parameters,the original pulse and shaped pulse can be viewed in real time through the software,which can quickly determine the best working parameters of the instrument.When measuring samples,the software can stabilize the spectrum and enhance measurement accuracy by adjusting the digital gain parameter.The test results show that the four-channel low-background alpha and beta spectrometer can normally measure and distinguish between alpha and beta rays.During measurement,the absolute pressure inside the measurement chamber is maintained below 30 Pa.The background count rate of the instrument for alpha rays is less than 1 cm^-2·h^-1,and for beta rays,it is less than 30 cm^-2·h^-1.The repeatability of alpha counting is up to a maximum of 0.35%,and the repeatability of beta counting is up to a maximum of 0.54%.The maximum cross-talk ratio of alpha rays to the beta channel is 0.520%,and the maximum cross-talk ratio of beta rays to the alpha channel is 0.013%.更多还原