Stabilizing scintillation detector systems: determination of the scintillator temperature exploiting the temperature dependence of the light pulse decay time

Scintillation detectors must tolerate a wide range of ambient temperatures and strong temperature slopes when used in outdoor applications. Such demanding conditions are typical for all homeland security applications. An effective and efficient detector stabilization compensating for temperature dependent gain shifts is essential to maintain energy calibration and resolution. Reliable, well established solutions are based on radioactive reference sources; however, alternatives are much asked for. The gain shift correction for the temperature dependence of the scintillation light output requires elaborate hard and software means without a reference source. Strong and rapid temperature changes further complicate the situation as there is no thermal equilibrium in the detector but rather a temperature field. Our paper demonstrates the measurement of an effective scintillator temperature by analyzing the pulse shape of detector signals. The pulse shape is correlated with the scintillation light decay time which can be extracted online from the digitized signals. The decay time data are used to eliminate all the temperature determined system gain shifts without radioactive reference source. This new stabilization procedure has been verified in extensive climate chamber measurements. The results are discussed.