Electron Response of Nal(Tl) and a Comparison with Anthracene and Pilot B

An investigation was made of the relative response of NaI(Tl) to electrons over an energy range of 6 keV to 1 MeV. The light output at 6 keV is quite sensitive to the nature of the exposed surface. The results are given for the two best cleaved NaI(Tl) crystals and compared to the electron response deduced from photon data. There is good agreement above 20 keV, where little sensitivity to changes in surface condition was observed. Similar measurements were made for anthracene and Pilot B. The relative light output per unit energy is shown for all three scintillators. Their merit as low energy electron detectors was found to be significantly affected by the amount of backscattering and the intensity and duration of long lived excitation states arising from ionizing events.