Temperature Character Analysis And Adjustment Technique For The Detector Of Aerial Gamma-ray Spectrometric

The aerial radiometric survey is only be used to find the radiological sources, but now it is widely be used in many fields. Do contribution to the stability of society and the development of economy. With the development of china's nuclear power industry, the demand for the uranium ore resources will be increasing inevitably, the aerial gamma-ray spectrometry as a tactic nuclear geophysical technology method, will play an important role in the future.At present, the airborne gamma-spectrometry which research and development by domestic have 4 channels, there is still a gap compared with the foreign countries. So developed an airborne gamma spectrum meter with independent intellectual property rights and the main performance indicators have reached international advanced level or the leading has become a top priority is urgency. It is of great significance for the airborne gamma-spectrometry technology and large system research and development capacity. This paper rely on the "863 Program" the research of aerial gamma-ray spectrum exploration systems, have a fundamental research in the temperature characteristic of the probe, through a series of experiments to find out the orderliness of temperature drift, provide guidance for system calibration and equipment R&D.For spectrum measure system, how to improve the stability and overcome spectrum drift is never comes easy to us. Compare to the ground gamma-ray spectrum measurement, the aerial gamma-ray spectrometry is often affected by the special environment (the width range of temperature, the complex environment of electromagnetism, the aerial electrical source is unstabilized and so on), the measurement results are existence of the larger error. The precision of measurement is impact by spectrum dirft. So the probe of aerialγ-ray spectrometry system is structured by NaI (T1) crystal with large volume cooperate with a large area photomultiplier tube. However, because of their poor consistency, poor uniformity, performance parameters easily be affected by temperature, meanwhile the photomultiplier tubes and other electronic components are vulnerable to the stability under the impact of temperature change, these factors will cause the output spectrum nonlinear drift for spectrometer system, a certain impact on the measurement accuracy. Based on this, by theoretical and experimental methods, some key problems were lucubrated, such as the temperature character analysis for detector of aerial gamma-ray spectrometric and adjustment technique. Designed an automatic spectrum stabilization circuit to carry out a preliminary calibration drift, it is very important significance for accuracy measurements for the aerialγ-ray spectrometry system, and lay the foundation for the next step fine-tuning.The aerial gamma ray spectrometry system required that the spectrum drift is less than±1 channel (512channel). So, the system's spectrum stabilization is the key factor for measuring result. This paper mainly presents the temperature dynamic of NaI(T1)detector's main structurement. Discuss the spectrum drift caused by temperature fluctuation. A great deal of experiment data has been done in order to build the mathematical model between the changing quantity of temperature△T and the high voltage changing quantity of photo-multiplier-tube(PMT)△VH. By utilizing high voltage with temperature compensation and temperature detecting technique, the photomultiplier's gain variation is stability. So the spectrum drift caused by temperature fluctuation is assumably be reduced. Make sure the system is mainly stabilization in the measurement.The main production and innovation are:(1) Through a long-term temperature experiment for large crystal of NaI(T1) scintillation detector, Obtained a large amount of data, include of the temperature and the output spectrum temperature drift of the detector's characteristic peaks, laid the foundation for the correction of the spectral drift.(2) Established a mathematical model of spectral drift correction, a function relationship between the changing temperature and high voltage changing of PMT was setting by fitting a large amount of data.(3) Developed automatic temperature compensation circuit for drift correction, use the mathematical model to achieve automatic temperature compensation and drift correction, for the realization of system's stability and first correction adjustment.Spectrum stabilizing was done by controlling the high voltage of the PMT in this study, this method is simply and trustiness, it can be effectively used to increase the measurement reference searching peak precision.