Research On Detection Spectrometer Of Deep Sea In-situ Gamma Radiation Environment

Exploring the deep sea is a hot topic in the 21 st century.Because deep sea contains a lot of valuable wealth on earth,such as mineral resources including metal minerals and submarine oil and gas,biological resources including rich biodiversity and genetic resources,and other resources for exploring the earth's structure and human history.Because most of the deep-sea resources contain radioactive gamma rays,the use of gamma radiation detector can identify and distinguish different deep-sea resources,which is of great significance for deep-sea exploration.The traditional deep-sea gamma radiation detection uses the non-in-situ method.The samples are collected at fixed points and then brought back to the laboratory for analysis.However,the in-situ detection has obvious advantages over the traditional method.This way is to combine the information to be observed with the real marine environment,continuously obtain real-time data,and truly reflect the status of marine environment and resources.The traditional in situ environmental gamma radiation detection spectrometer is generally divided into fixed type(long time detection in a place)and mobile type(moving detection underwater with mobile tools).At present,many countries,such as Europe,America and so on,have done some research on deep-sea gamma radiation detection,and achieved important research results,but there is still a blank in this field in China.Based on the gamma detection technology in nuclear physics experiments,combined with the existing international underwater gamma detection methods,aiming at the special deep-sea environment,facing different platforms in the deep sea,in order to achieve the effect of fine detection of radionuclides and rapid mobile census,this paper will carry out the research of new high-resolution and high-efficiency gamma detection key technology.In this paper,a high-resolution gamma spectrometer is designed based on a novel semiconductor(CdZnTe)detector.Due to the high energy resolution,no extra refrigeration and small volume of CdZnTe detector,the detection efficiency of different thickness and arrangement is studied by Monte Carlo simulation.Then,according to the detector signal,the readout electronics scheme with multi-channel charge sensitive front and digital filter is designed.In order to adapt to the special marine environment,this paper designs the inner core structure and titanium alloy capsule shell protection structure.Finally,the electronic test and performance test of the spectrometer are carried out,and the test results meet the requirements.In this paper,a high efficiency gamma spectrometer based on scintillation detector is designed.In this paper,the different scintillation,photoelectric converter and readout electronics scheme and structure design are studied.Finally,two schemes are selected for design.One is based on a 3-inch NaI(Tl)scintillator coupled photomultiplier tube,using waveform digital signal acquisition readout electronics design.The other is four 1-inch NaI(Tl)scintillator coupled avalanche photodiodes with multi-channel charge sensitive readout electronics and digital filtering.The corresponding structures of the two technical routes are designed,and the corresponding electronic test and spectrometer performance test are carried out.The two schemes have their own advantages and disadvantages,but the test results meet the requirements.Finally,the semiconductor gamma spectrometer and several small size NaI(Tl)scintillator coupled avalanche photodiode gamma spectrometer were selected for the sea experiment.Energy calibration,dose calibration,water simulation and temperature change were carried out before the experiment.Finally,the two spectrometers carried out the sea test in the South China Sea with the deep submergence vehicle.The sea test results show that the system works stably and reliably,and obtains effective scientific data.