An automated drift correction method for in situ NaI(Tl)-detectors used in extreme environments

Abstract

Gamma-ray detection systems are exposed to extreme environments during in situ measurements and the NaI(TI)-detectors in these systems are frequently subjected to significant temperature fluctuations. Several elements within these detectors are sensitive to temperature deviations, which ultimately causes a drift in gamma-ray spectra. This study aimed to determine the relationship between temperature deviation and spectrum drift and found a linear relationship over a wide range of energies. It was found that an increase in the detector temperature shifts the gamma-ray spectrum to lower channels, whereas a decrease in the detector temperature shifts the spectrum to higher channels. Using this information, a novel drift correction method based on the Gaussian distribution of the 1460 keV gamma-peak of ⁴⁰K was developed. Dividing the peak into five regions of interest (ROI), a weighted gain correction factor is calculated based on the comparative skewness of the measured data and the sensitivity of the drift. The detector gain is then adjusted by the same factor to correct the drift in gamma-spectrum. This method was first tested in a simulated in situ environment, followed by in situ measurements along a beach. As expected, the gain adjustments followed the trend in detector temperature. The corrected counts in each of the five bins also presented good results and a close fit to the Gaussian distribution.

Keywords: Drift correction; Gaussian; NaI(Tl); Temperature; in situ.