Low Drift, Multi-channel Spectrometer Developed A Portable Computer

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℃.