Study of Statistical and Non-statistical Components of Energy Resolution for High-sensitive Beta Camera

Energy resolution of a scintillation detector was studied from the viewpoints of statistical and non-statistical components. The statistical component is caused mainly by fluctuation of the number of photoelectrons, N, collected at the anode of a photodetector and the non-statistical component comes from intrinsic property of the scintillator. A new method identifying these two components was developed to study the resolution of detector as beta camera. The beta camera consists of a 6 cm times 6 cm times 1 cm plastic-scintillator plate (BC-408 provided by SAINT GOBAIN) and 4 photomultiplier tubes covered each side face of the plastic-scintillator. The statistical component is found to be well reproduced by 1/radicN. The non-statistical component of the plastic-scintillator is sigma_stat = 4.0 plusmn 0.3 % (DeltaE/E = 9.3 plusmn 0.8 % in FWHM) at the 976 keV region. The present method is useful for investigating statistical and non-statistical components of the resolution, and thus to improve and monitor them.