Collimated Beam Scanning of Pure Germanium Detectors

The design of collimated sources of Am241, Co57, and Fe55 suitable for scanning germanium detectors is given. Am241 scans taken through the p contact on a p-type detector are given for detectors with and without radial resistivity gradients. The data obtained from these scans are used to calculate the radial dependence of depletion layer width and an "effective" carrier concentration. The results obtained indicate that, with the surface treatment used, the surface is accumulated on p-type detectors. At voltages below full depletion, an extra "peak" associated with slow pulses originating in the undepleted region is described. The number of these slow pulses depends on the type of back contact that is used.