Charge Collection in Coaxial Ge(Li) Detectors

Cylindrical double-open-end coaxial Ge(Li) detectors have been studied at 77°K using a small-area (circular) collimated beam of 137Cs ¿-rays. The beam was aimed parallel to the detector axis and moved across a diameter. On different detectors, different trapping effects were observed; one detector gave better resolution and a greater pulse height when irradiated near the p-type core, another gave best performance when irradiated near the outer n+-layer. The observed pulse shapes for different positions of irradiation showed general agreement with calculated pulse shapes based on an assumed r-1 variation of electric field across the i-region.