Correlating the Luminosity Parameters to Pulse Shape Discrimination

Monte Carlo simulations were used to investigate the correlation between luminosity parameters and pulse shape discrimination (PSD) and subsequently compared with experimental results from CsI:Tl. Luminosity intensity parameters A_f, As (fast and slow initial luminosities) and temporal luminosity parameters τ_f, τ_s (fast and slow decay time constants) of a dual decay mode scintillator were applied to create a dynamic model with Crystal Ball simulation system. The simulated pulses were analyzed with charge comparison (CC) and constant time discrimination (CTD) PSD methods followed by quantification of the histogrammed pulse data with Figure of Merit (FoM) and spillover (pulse misclassification). Performance in terms of FoM and spillover is compared with that of fixed reference pulses set at (A_f τ_f/A_s τ_s)_γ = 1 and (A_f τ_f/A_s τ_s)_γ = 0.1. For the CC method, independent of the reference pulse characteristics [(A_f τ_f/A_s τ_s)_γ = 1 or = 0.1], τ_s is the most influential parameter for PSD as compared with A_f, A_s, and τ_f. For the CTD method, A_f and As are seen to have less influence over the PSD compared to τ_f and τ_s when (A_f τ_f/A_s τ_s)_γ = 1 and τ_f is the most influential parameter for both reference pulses. Using both methods with either reference pulse applied, the scintillator having luminosity parameters such that is classified as having poor PSD. Excellent correlation is observed between the simulation and the experimental results with CsI:Tl, which is known for very good α/β(- γ) pulse shape discrimination. This study is useful for describing how the luminosity parameters affects PSD.