A study on “position-energy” response correction method based on monolithic crystal coupled SiPM array

The intrinsic characteristics of the monolithic crystal detector are spatially inconsistent, which leads to the position dependence of the detector on the energy response of the γ-ray as well as the peak shift of the response spectrum of the detector, that is, the “position-energy” shift. The “position-energy” shift will cause the energy resolution of the detector to deteriorate and affect the energy linearity of the detector. Thus, a crucial challenge in enhancing the position consistency of detector energy response, improving energy resolution, and ensuring accurate isotope identification is the reduction or elimination of this “position-energy” offset. The “position-energy” response correction method is proposed in this paper to improve the position consistency of detector energy response. Firstly, Monte Carlo simulation is used to model monolithic LaBr₃(Ce) crystal detectors of different sizes. Secondly, the effective detection region of the detector model is evenly divided into 25 blocks, then the spectral peak position of each incident region is extracted, and the spectral peak correction function matrix of 25 incident regions and the center position is established. Finally, 25 incident regional peaks are modified according to the modified function matrix, so that the spectral peaks in each region are consistent with the peaks in the center, and the modified spectral responses of the detector are obtained. The simulation results show that this method can effectively solve the “position-energy” migration problem of monolithic crystal detectors of different sizes and improve the peak consistency of each detector region. The energy resolution of the 662 keV characteristic peak of the Cs-137 point source can be improved from 4.5% to 3.9%, and the linear deviation of energy can be reduced from 2.1% to 1.2%.