Development of a light yield calibration method for [formula omitted]SR detectors based on Compton edge location

Abstract

A highly segmented muon spin rotation/relaxation/resonance (μSR) spectrometer with over 2500 channels has been proposed in the construction of Phase II of the China Spallation Neutron Source (CSNS). Plastic scintillators are chosen as the detector material due to their high sensitivity to charged particles and good flexibility to various geometries. Gamma-ray sources are commonly used to calibrate the light yield of plastic scintillators. Accordingly, a derivative method has been developed to efficiently locate the Compton edge in gamma-ray spectra. In this method, the minimum and width of the derivative data are regarded as the position of the Compton edge and an estimation of energy resolution, respectively. Both experiments and simulations demonstrate the good reliability of this method for Compton edge positioning and energy resolution characterization. The derived Compton edge shows a systematic shift to the right of its real location. The relative shift is proportional to the energy resolution with a factor of ∼0.13. The assumed energy resolution should be corrected by a factor of ∼1.19 which is confirmed by inorganic scintillator measurements. In the measurement of plastic scintillators, the assumed Compton edge and energy resolution can well reproduce the energy response spectra for different types of gamma-ray sources.