Forward calculation of airborne gamma 3D radiation fields based on rapid coupling method of point kernel integrals

Airborne gamma ray spectrum detection technology is an effective means to measure the concentration and spatial distribution of natural radionuclides in environmental media such as surface rocks and soil during aviation flight. Therefore, it is vital to fully explore the radiation information related to mineralization in airborne gamma spectrometry data and explore the dose distribution law of gamma radiation field of radionuclides in the detection area. This paper is based on the theoretical calculation model of ground-air interface gamma radiation field. After discretizing the equivalent surface source of the geological body with irregular and uniformly distributed radionuclides into a grid, it is divided into differential surface sources of uniform size, density, and isotropy. A theoretical calculation model for the spatial radiation field of differential surface sources at the ground-air interface has been derived. Finally, a rapid calculation program for the 3D radiation field of irregular surface sources coupled with point sources has been developed using the Qt framework. The accuracy and efficiency of the program were tested through three examples. For a single regular surface source, the rectangular surface source exhibited higher consistency at most detection points. The average relative deviation was 9.183%. In the case of a circular surface source, the dose rate values between the two methods deviated more significantly in the edge regions but less so in the central region. The average relative deviation was 12.765%. When comparing the calculation data of two irregular surface source models, the rapid calculation program was dozens of times faster than the SuperMC program. The maximum relative deviation was 38.245%, the minimum relative deviation was 5.416%, and the calculation accuracy was high. The average relative deviation was 21.912%. On several irregular surface source models, the relative deviations were relatively large. The maximum relative deviation reached 52.234%, the minimum was 12.305%, and the average relative deviation was 28.126%. This study can provide a certain theoretical reference for researchers in related fields, promoting the development and application of airborne gamma radiation field technology.