Improvement of a spectrum-to-dose conversion function for electronic personal dosimeters

Abstract

For electronic personal dosimeters (EPDs) based on a spectroscopy system, it is necessary to accurately measure the dose in real-time from the gamma energy spectra. The method of spectrum-to-dose conversion is being used instead of the method of count-to-dose conversion. The G(E) function, a typical method of spectrum-to-dose conversion has been applied to various instruments due to its good dose measurement performance and the advantage of real-time measurements. In this manuscript, we present a method to increase the accuracy of G(E) function for the EPD consisting of a 3 × 3 mm2 PIN diode coupled with a 3 × 3 × 3 mm3 CsI(Tl) scintillator. The new G(E) function was calculated using the adaptive moment estimation (ADAM) method based on Monte Carlo simulation. The proposed G(E) function is verified by comparison with the least-square method (LSM), which is the conventional method for calculating the G(E) function and with the gradient-descent method (GDM), which is the basis for the ADAM. The relative difference was acquired to compare the converted dose value using each G(E) function by using 241Am, 57Co, 22Na, 137Cs, 54Mn and 60Co radioisotopes. In addition, the energy response to 137Cs of each G(E) function was obtained. The relative difference of G(E) function according to LSM, GDM, and ADAM was in the range of ±28.54, ±12.59, and ±9.9%, respectively, and the energy response to 137Cs was 0.71 to 1, 0.87 to 1.02, and 0.9 to 1.03, respectively.