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

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 ?? 10⁶ pulses/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 of ⁶⁰Co at 4 ?? 10⁶ pulses/s is 7.6%, with only 14% of lost pulses from the channels of interest.