Correlation of Local Trapping with Crystal Defects by Direct Observation of Electron Loss in a Coaxial Ge(Li) Detector

A propeller-shaped region of reduced full-energy-peak efficiency was observed on the face of a true coaxial Ge(Li) detector. A similar pattern on the etch-pit photograph suggests that the propeller blades correspond to the 1 1 1 symmetry axes of the crystal. Spectra obtained when a 122 keV γ-ray beam was directed at this degraded region, show a low energy tail which is not present when the beam is directed at normal regions. Current pulses corresponding to γ-rays that interact in the propeller region have shapes that show deficiencies in the electron component. Thus, degraded crystal regions that are revealed by etch-pit distributions can be correlated to local detector performance by direct observation of trapping rather than only by inference from the presence of tails in the energy spectra.