Simulation method of airborne radiation detector response based on the equivalent transformation

In airborne gamma radiation measurement, radiation detectors' responses are simulated using the direct simulation method. However, the number of particles recorded by the detector is significantly lower than the number of particles emitted from the radiation source. This imbalance leads to low simulation efficiency, making it challenging to achieve an acceptable level of statistical uncertainty within a limited computer time. To address this inefficiency, we have theoretically proven the equivalent transformation and utilized that to devise a fast Monte Carlo simulation method known as the equivalent transformation method. Simulation results from a large body and a large surface source demonstrate that the detector response spectrum calculated using the equivalent transformation method closely agrees with those obtained through the direct simulation method. Furthermore, the efficiency ratio for the equivalent transformation method, in comparison to the direct simulation method, stands at 2.37 x 106 and 2.67 x 106 for a large body and a large surface source, respectively. These findings solidify the validity and effectiveness of the equivalent transformation method in enhancing simulation efficiency for the research on airborne gamma radiation measurement.