Optimization of the integration time of pulse shape analysis for dual-layer GSO detector with different amount of Ce

Abstract: For a multi-layer depth-of-interaction (DOI) detector using different decay times, pulse shape analysis based on two different integration times is often used to distinguish scintillators in DOI direction. This method measures a partial integration and a full integration, and calculates the ratio of these two to obtain the pulse shape distribution. The full integration time is usually set to integrate full width of the scintillation pulse. However, the optimum partial integration time is not obvious for obtaining the best separation of the pulse shape distribution. To make it clear, a theoretical analysis and experiments were conducted for pulse shape analysis by changing the partial integration time using a scintillation detector of GSOs with different amount of Ce. A scintillation detector with 1-in. round photomultiplier tube (PMT) optically coupled GSO of 1.5mol% (decay time: 35ns) and that of 0.5mol% (decay time: 60ns) was used for the experiments. The signal from PMT was digitally integrated with partial (50–150ns) and full (160ns) integration times and ratio of these two was calculated to obtain the pulse shape distribution. In the theoretical analysis, partial integration time of 50ns showed largest distance between two peaks of the pulse shape distribution. In the experiments, it showed maximum at 70–80ns of partial integration time. The peak to valley ratio showed the maximum at 120–130ns. Because the separation of two peaks is determined by the peak to valley ratio, we conclude the optimum partial integration time for these combinations of GSOs is around 120–130ns, relatively longer than the expected value. [Copyright &y& Elsevier]