GAMMA-RAY DETECTORS FROM THERMALLY ANNEALED BRIDGMAN-GROWN CDTE

The characteristics of small gamma-ray probe detectors (hemispherical contact geometry) made from Cl- and In-doped Bridgman-grown crystals o f CdTe are described. A slow, low-temperature anneal of as-grown CdTe ranging from 485 to 85-degrees-C, and cooled at a rate of < 20-degrees -C/h, was found to greatly improve detector performance. Best photopea k to Compton edge ratios were 2:1 for 662 keV gamma-rays. Typical valu es were 1:1 with energy resolutions of 5% full width at half maximum. Energy resolution was approximately 13.5% for 185 keV gamma-rays from a U-235 (93%) source.