Digital pulse height correction in HgI2 γ-ray detectors

We report on the application of digital pulse processing algorithms to improve the spectroscopic performance of a 1.2 mm thick planar HgI2 gamma-ray detector. We have used offline processing of pulses which were recorded using a high resolution waveform digitizer. The recovery processes include long duration shaping to avoid ballistic deficit in the case of slow pulses, and the application of biparametric correction techniques to compensate for charge loss. Pulses of duration as long as 100 mu s were recorded to facilitate long duration shaping. Two different pulse processing algorithms, viz. semi-Gaussian and moving window deconvolution, were applied and their performance was compared. The application of long duration shaping and digital charge-loss correction improved the energy resolution at 662 keV by more than 20% and the peak to background ratio by a factor of two. The resolution and the peak to background ratio were further seen to improve drastically upon rejection of counts with very slow rise-time. A 2.6% energy resolution at 662 keV with 14:1 peak to background ratio was obtained.