Improving the Energy Resolution of BaF₂ Scintillators by Cooling

Abstract

The energy resolution at 662 keV of a BaF₂ scintillator improved from 9.5% at 28 °C to 8.8% at −5 °C. Further cooling deteriorated the resolution. Experiments with a long quartz light guide disprove the idea that the unintentional cooling of the photocathode of the photomultiplier is responsible for the levelling off of the resolution at lower temperatures as suggested by Wisshak et al. We present evidence that irradiation defects at temperatures below 0 °C limit the resolution.