High Count Rate Gamma Ray Pile-Up Correction Method of NaI(Tl) Detector Based on Deconvolution Method

The output pulses of NaI(Tl) detectors have long tails due to the long decay constant of their output circuits, and these pulses easily pile up in high-count-rate environments. In this study, we used digital deconvolution combined with a digital filtering algorithm to restore piled-up pulses as separate, narrow, Gaussian-like pulses. Radioactive isotopes were used to calibrate the amplitudes of the signals processed by the proposed method. The gamma spectra with different methods were obtained to verify the proposed methods. Count rates were tested at various source-detector distances, and Monte Carlo simulation data verified that the error was within 14.60 % for count rates up to 1661 kHz. Compared to a commercial digitizer, for event rates up to 851 kHz, the proposed method increased the count rate by a factor of 53 and increased the energy resolution from 21.44 % to 15.50 %, while the energy resolution without pile-up was the same as that of the digitizer.