The Ambient Dose Equivalent Measurement by the Spectro-Dosimeter Method in the NaI(Tl) Detector

A minimum level of radiation needs to be detected for determining the value of the radiation dose equivalent. Typically, the output of a nuclear radiation detector cannot be used directly for determining the value of the radiation dose equivalent. Via changing the response function or the readout of the detector, effort is made to obtain a logical relation between the output of the detector and the dose equivalent. For this purpose, various hardware and software methods are used. In this research, the ambient dose equivalent H*(10) of gamma radiation is determined by applying the spectro-dosimeter method, which is based on the software method. In this method, the readout of the NaI(Tl) detector is subdivided into several energy intervals based on the pulse height, thereby, each energy interval has its own conversion factor. Conversion coefficients are obtained by using the Gaussian elimination method. The ambient dose equivalent H*(10) is determined from the detector readout without spectra deconvolution. Using the Geant4 Monte Carlo code simulation, the response function and the readout of the NaI(Tl) detector for gamma radiation are determined and then the conversion coefficients are calculated for obtaining the ambient dose equivalent. Fairly good agreement is observed between the simulation data and experimental results for the detector response function. The results show that by finding the conversion coefficients function in the energy range of 0.03-3 MeV in this dosimetric method for values equivalent to the ambient dose of gamma the measurement error percentage decreases and the measurement accuracy increases.