Calculation and Research of γ-ray Air Attenuation Coefficient at Different Altitudes

Abstract

In the process of aviation gamma dose rate measurement, due to the large altitude span, the gamma-ray air attenuation coefficient will be affected by altitude, temperature, air pressure and air density, so corresponding corrections are needed. The Monte Carlo method is used to simulate the linear attenuation coefficient of γ-ray in the air at different densities. First, use empirical formulas to calculate the air density at different altitudes; then use MCNP software to build a gamma spectrometer model to calculate the gamma photon fluence at different altitudes and different densities; finally, calculate the air density at different air densities based on the principle of exponential decay line attenuation coefficient. The results show that the maximum relative error between the air quality attenuation coefficient obtained by the air density simulation calculated by the empirical formula and the recommended value of NIST in the United States is -17.3%; the attenuation plate is used for experimental verification in the γ-ray reference radiation field, and the results show the theoretical calculation and the actual measurement relative error of value: the maximum relative error of 60Co source is 6.0%, and the maximum relative error of 137Cs is 5.3%. This work lays the foundation for the follow-up study of low-altitude near-earth radiation dose.

Keywords

• aerial measurement
• altitude
• γ-rays attenuation coefficient
• monte carlo
• reference radiation field