Airborne gamma-ray spectroscopy for modeling cosmic radiation and effective dose in the lower atmosphere

TL;DR

This study used airborne gamma-ray spectroscopy over the Tyrrhenian Sea to separate cosmic and terrestrial gamma signals, calibrate background levels, and estimate the cosmic radiation dose affecting humans.

Contribution

It introduces a method to distinguish cosmic from terrestrial gamma signals in airborne surveys and relates cosmic count rates to effective human dose using calibration tools.

Findings

Successfully separated cosmic and terrestrial gamma signals at various altitudes.

Calibrated background gamma-ray levels for accurate terrestrial radioisotope estimation.

Estimated annual cosmic radiation dose to humans based on airborne measurements.

Abstract

In this paper we present the results of a $\sim$5 hour airborne gamma-ray survey carried out over the Tyrrhenian sea in which the height range (77-3066) m has been investigated. Gamma-ray spectroscopy measurements have been performed by using the AGRS_16L detector, a module of four 4L NaI(Tl) crystals. The experimental setup was mounted on the Radgyro, a prototype aircraft designed for multisensorial acquisitions in the field of proximal remote sensing. By acquiring high-statistics spectra over the sea (i.e. in the absence of signals having geological origin) and by spanning a wide spectrum of altitudes it has been possible to split the measured count rate into a constant aircraft component and a cosmic component exponentially increasing with increasing height. The monitoring of the count rate having pure cosmic origin in the >3 MeV energy region allowed to infer the background count rates in the $^{40}$K, $^{214}$Bi and $^{208}$Tl photopeaks, which need to be subtracted in processing airborne gamma-ray data in order to estimate the potassium, uranium and thorium abundances in the ground. Moreover, a calibration procedure has been carried out by implementing the CARI-6P and EXPACS dosimetry tools, according to which the annual cosmic effective dose to human population has been linearly related to the measured cosmic count rates.