Simultaneous recording of high energy photon spectrum in phoswich detectors

Phoswich detector with PSD electronics has been routinely used for lung counting at RSD, Indira Gandhi Centre for Atomic Research. The PSD electronics has been optimized for obtaining only low energy photon (LEP) spectrum upto 200 keV. The pulses resulting from the NaI(Tl) portion i.e, mainly LEP interaction are selected by the PSD and used for the measurement. The pulses from the CsI portion i.e, mainly high energy photon (HEP) interactions are utilized only for the PSD electronics and are not being utilized for any spectral measurements. But processing of pulses originating from the CsI can also provide valuable information about HEP photon emitters if any during the in vivo monitoring. This requires modification the PSD electronics and two multichannel analysers for simultaneous recording the energy spectra derived. While the modification is done, care was taken not sacrifice the quality and fidelity of low energy monitoring. The phoswich detector with modified PSD electronics configuration enabled us to simultaneously record both LE photon and HE photon spectra from a single phoswich detector. The system performance evaluation showed that the system with new PSD configuration has very good gamma spectrometry characteristics. Analysis of recorded room background REP spectrum brought out the trace level detector contamination of 137Cs. The interference of 41Ar could be easily identified and its contribution to lower energy regions is quantified