Benchmarking NaI(TI) electron energy resolution measurements

NaI(Tl) electron energy resolution η_e determined for electron energies ranging from 16 keV to 437 keV was validated. The Compton coincidence technique (CCT) previously used for characterization of scintillator light yield nonproportionality, was slightly modified for use in the present study. Measured η_e, values range from 24% at 16 keV to 6.7% at 437 keV. η_e values determined represent variations in: light production from monoenergetic electrons (including effects due to light yield nonproportionality), light collection at the photomultiplier tube (PMT) photocathode, photoelectron production, photoelectron collection at the first dynode, and PMT gain, as well as noise from the accompanying electronics. To verify the accuracy of the MCCT-measured η_e, values, the total gamma-ray energy resolution η_e, was calculated based on Monte Carlo simulations, a simplified cascade sequence, and η_e. The resulting calculated η_γ values are then compared with measured η_γ values. Agreement to within 5% was observed for E_γ > 40 keV between the calculated and measured η_γ results. However, a discrepancy was observed between the calculated and measured values for E_γ < 40 keV. Results from this study provide insight into the significance of light yield nonproportionality and its contribution to energy resolution.