低漂移便携式微机多道能谱仪的研制

【作者】 王广西；

【导师】 赖万昌；

【作者基本信息】 成都理工大学 ， 核技术及应用， 2006， 硕士

【摘要】 NaI(T1)单晶γ能谱仪具有探测效率高、使用方便、价格低廉等优点，在放射性勘查、辐射环境评价等领域得到了广泛的应用。但是NaI(T1)闪烁探测器具有明显的温度效应，在野外环境下使用时，会产生严重的谱漂，影响测量的精度。如何克服谱漂和提高稳定性是谱仪研制中的一个难题。 本文采用温度动态跟踪和谱峰实时校准的稳谱模式，开发一种具有高稳定性的野外γ能谱仪。仪器采用一体化探头和微机化主机的“模-数”分离式结构，提高了仪器的抗干扰能力和稳定性。一体化探头以AT89S52单片机为控制核心，将射线探测、信号放大与成形、脉冲幅度分析、数据缓存等部件集中在一起，使探头与主机之间的信号传输由传统的模拟信号改为抗干扰能力强的数字信号。通过带温度补偿的高压电源和温度跟踪技术，较好地克服了光电倍增管二次发射系数变化所造成的增益变化及其它部件的温度效应，大大降低了温度变化对谱漂的影响，在硬件上保证了仪器谱的稳定。同时，采用软件自动寻峰和谱峰函数重建技术，建立实时校准特征峰强度的计算模型，有效地消除了谱漂的影响。仪器的主机由嵌入式计算机、液晶显示器、触摸式键盘以及应用软件等组成，完成数据处理、存储和人机交互功能。应用软件包括自动测量、手动测量、参数设置、文件管理、谱处理、数据处理、联机通讯等模块，可满足一般γ能谱测量的需要。仪器经中国测试技术研究院检定，U、Th、K含量测量结果的不确定度分别为：6％、6％、10％。试验结果表明，仪器在-10℃～40℃温度范围内工作，谱漂小于±1道。更多还原

【Abstract】 NaI(TL) crystal gamma-ray spectrometer has been applied comprehensively on the fields, such as radioactive survey, radiation environment assessment because of the advantages of high detection efficiency, convenience and low cost. But NaI(TL) detector has significant temperature effect, which will bring such serious spectrum drift that accuracy of measurement is be lowered in field environment. So how to improve the stability and cope with spectrum drift is still an arduous problem.This paper mainly presents an in situ gamma-ray spectrometer with high stability is developed by using the spectrum stabilization model of temperature dynamic tracking and spectrum peak instantaneous calibration, which based on the separate structure of integrated detector and computerized control platform. By integrating gamma-ray detection, signal amplification and formation, multi-channel pulse-height analyzer and data buffer in the integrated detector with AT89S52 as the control core, both the capability of anti-interference and the stability are significantly improved which turn analog signal into digital signal between detection and control platform. By utilizing high-voltage with temperature compensation and temperature detecting technique, the gain variation because of secondary emission coefficient of photomultiplier and the temperature effect of other components are resolved ideally, so the spectrum drift caused by temperature fluctuation is markedly minished, and the stability of instruments spectrum is greatly advanced on hardware. The influence of spectrum drift is eliminated effectively, on condition that the computation model of instantaneous calibrating characteristic peak is established by using automatic software peaksearch and spectrum line reconstruction technique. Control platform is composed of embedded computer, LCD, soft keyboard and gamma-ray spectrum analysis software, which achieve data processing, data storage and Man-Instrument interaction. Meanwhile gamma-ray spectrum analysis software includes automatic measurement, hand measurement, parameter setting, file management, spectrum processing, data processing and interconnect communication etc. The uncertainty degrees of measurement results of the contents of U, Th, K are 6%, 6% and 10% has been certified by National Institute of Measurement and Testing Technology. The results of test show that spectrum drift is less than ±1 channel in the range of -10℃ ~40℃.更多还原