Least squares arrival time estimators for single and piled up scintillation pulses

A new time arrival estimator is developed for the detection of gamma rays using scintillation detectors. The estimator structure reduces to a weighted least squares (WLS) estimate of the arrival time and is found to be the optimal estimator for scintillation pulses. This WLS estimator is applied to scintillation type pulses with fast rise times and exponential decays. The timing resolution is calculated and compared to the resolution of leading edge and constant fraction triggers for a Burle 8850 photomultiplier tube, and to the Cramer-Rao lower bound on estimator performance. The WLS estimator outperforms these conventional arrival time estimators and has the added ability of simultaneously estimating the arrival times of multiple overlapping pulses. This allows for piled up pulses to be effectively separated permitting their individual energies to be estimated