Digital pulse height correction in HgI₂γ-ray detectors

Abstract

We report on the application of digital pulse processing algorithms to improve the spectroscopic performance of a 1.2 mm thick planar HgI 2 γ-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 µs 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 chargeloss 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.

Biparametric analyses of charge trapping in Cd0.9Zn0.1Te based virtual Frisch grid detectors

“…It can be seen that the 662 keV events were inclined towards the high energy side of the actual peak position, which is in contrast to the normal hole trapping signature (inclination to the left side), e.g., in planar detectors. 20 This atypical behavior can be still attributed to hole trapping and de-trapping effect and can be explained as follows. Let us consider two instances of position of interactions marked as P1 and P2 in Fig.…”

Gamma Ray Detection with Cd0.9Zn0.1Te Based Detectors Grown Using a Te Solvent Method

“…Details on the digital spectrometer and biparametric correction scheme can be found in [5,7]. The energy resolution has been expressed in terms of full width at half maxima (FWHM) of the relevant peaks.…”

High energy γ-ray detection using CZT detectors with virtual Frisch grid

“…As mentioned before, biparametric plots help to visualize the correlation between two parameters of the pulses generated from the same set of events. Biparametric plots obtained from detectors in planar geometry shows the correlation between the depth of interaction and the corresponding pulse-height of a particular set of events [14,15], the depth of interaction being given by the rise-time of the pulses. In the case of high energy gamma rays, most of the signals generated is due to a mixture of both electron and hole movements.…”

“…7. However, digital correction scheme based on the biparametric correlation can be applied to compensate for most of the effects due to the charge loss in the trapping centers [14,15]. Figure 9 shows a corrected biparametric plot obtained by adjusting the events in a manner so as to get a uniform pulse-height distribution.…”