Pileup Correction Algorithms for Very-High-Count-Rate Gamma-Ray Spectrometry With NaI(Tl) Detectors

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In this paper, we propose algorithms that are suitable for gamma-ray spectrometric systems with Nal(Tl) detector that support pileup correction at extremely high count rates of 4 · 106pulses/s. The following two algorithms are presented: 1) an algorithm based on modified phase-only correlation (MPOC) for the detection of the beginning of pulses and maximum likelihood estimation (MLE) for the estimation of the pulses' amplitudes and 2) an algorithm based on the modified pulse clipping (MPC) method. Simulation results have shown that the systems based on both MPC and MPOC-MLE are capable of reducing pileup effects and improving the resolution of the energy spectrum at very high count rates. MPOC-MLE can support extremely high count rates while keeping good energy resolution. The resolution of60Co at 4 · 106pulses/s is 7.6%, with only 14% of lost pulses from the channels of interest.