Analytical expression to calculate total and full-energy peak efficiencies for cylindrical phoswich and lanthanum bromide scintillation detectors

A gamma ray sourceless efficiency calibration method based on the Boolean operation of the ray deposition process

The general sourceless efficiency calibration has two major methods, Monte Carlo simulation and numerical calculation. Monte Carlo simulation as an important method to address the efficiency calibration in complex measurement systems, despite it being highly accurate, but inefficient and time-consuming. And although the numerical calculation is computationally efficient, its accuracy is highly influenced by the multiple Compton scattering of rays in sensitive body, and it is difficult to deal with complex measurement systems. To solve the above problems, this paper proposes a discrete numerical calculation combined with the graphical Boolean operations method for sourceless efficiency calibration. The method starts with a Monte Carlo simulation to obtain the rays deposition process in an infinite sensitive body and record deposition locations as a matrix; then, for different measurement systems, discrete numerical calculations are used to rapidly obtain the transmission process of rays to the sensitive body of the detector; finally, the two are combined to obtain the detection efficiency of the rays by using graphical Boolean operations. For the given two test models, the error between the measured and calculated results of ²⁴¹Am, ¹³⁷Cs, ⁶⁰Co at 60 positions is within -3.61∼9.71%, and the error between the measured and calculated results of the soil source is within -1.27 to 4.26%, indicating that the method has high reliability in sourceless efficiency calibration. And in comparison with Monte Carlo simulations, it is found that the method has a good agreement with Monte Carlo simulation in efficiency calibration and the computational speed has been greatly improved.

Calibration of the Absolute Efficiency of Well-Type NaI(Tl) Scintillation Detector in 0.121–1.408 MeV Energy Range

Well-type NaI(Tl) detectors are beneficial for low-level photon activity measurements because of the near 4π solid angle that can be gained with them. The detection efficiency can differ with the source-to-detector system geometries, the absorption of the photon in the detector material, and attenuation layers in front of the detector face. For these purposes, the absolute efficiency and the coincidence corrections of the well-type sodium iodide detector have been measured at 0.121–1.408 MeV energy range (obtained from 152Eu, 137Cs, and 60Co radioactive isotopes). The covenant between the experimental (present work) and the published theoretical values is good, with the high discrepancies being less than 1%.