Preliminary Application For The Spectrum Data Of Lowerenergy Peak By Airborne Gamma-ray Spectrometry

Gamma-ray spectrometry is an important nuclear geophysical exploration method,which can be used to get the content of ground natural radionuclide uranium, thorium,potassium. Without considering the lower energy peak, people just use high energypeak to surveying peak information early. In fact the gamma-ray spectrum of lowerenergy contains abundant stratigraphic information, it has great significance if we canmake full use of this information.This paper study the full gamma-ray spectrum characteristics and analysis lowerenergy peak decay rule of uranium and thorium, based on the principle of airbornegamma-ray spectrometry. It regards1120keV uranium peak and911keV thoriumpeak as the research objects. Then it makes static calibration, dynamic calibration, andhigh altitude calibration with high-energy gamma-ray method and low-energygamma-ray method respectively. Finally, verifying calculation in the known standardcontent through the calibration data.According to the research of this paper, the following results can be drawn:（1）The results of dynamic belt counting rate ratio basically remain the same onthe top and under detector. In60meters,90meters and120meters high segment, thecounting rate ratio is respectively0.15,0.16and0.16; In the150meters,180meters,210meters,240meters and300meters height segment, the average counting rateratio is0.19.The study has an important significance in the influence of atmosphericradon and airborne gamma-ray spectrometry.（2）It is complex to get Compton scattering coefficient, high attenuationcoefficient, the airborne background and cosmic rays, using airborne gamma spectrumdata of static calibration, dynamic calibration and high altitude calibration. In thestatic hybrid model, the error of calculating content result error is less than5%withboth high energy gamma-ray method and lower energy gamma-ray method. （3）Validated in the dynamic model, the average thorium content was calculatedby the spectrum data of high energy peak is8.4710-6, the average uranium contentis1.8610-6, potassium content of average is1.79%in60meters,90meters,120meters,150meters and180meters. Also, the average thorium content was calculatedby the spectrum data of lower energy peak is12.4010-6, the average uranium contentis3.7610-6, potassium content of average is2.50%. The results proves that thedynamic calculation with high-energy peak of three natural radioactive nuclide isclose, compared to standard values using gamma-ray spectrometry of HPGe detector(thorium content is8.4810-6, uranium content is2.0310-6, potassium content is1.79%),and the result content of low-energy is on the high side.In conclusion, it is feasible to get the content of ground natural radionuclideuranium, thorium, potassium using the spectrum data of lower energy peak byairborne gamma-rayspectrometry, but it remains to be further research.