Neutron damage tests of a highly segmented germanium crystal

To evaluate the effect of neutron damage on the performance of highly segmented germanium detectors the P3 prototype detector for the GRETINA array was subjected to a neutron flux of ∼3×109 n/cm2 over a period of 5 days. During the irradiation, the resolution (full-width half-maximum (FWHM)) of the 1332 keV 60Co photopeak increased from ∼1.8 to ∼6.0 keV while the full-width at tenth maximum (FWTM) increased from ∼4 keV to more than 12 keV. Following the irradiation the detector was successfully annealed and the energy resolution returned to pre-irradiation values. All detector segments were fully functional before and after the annealing and following multiple room-temperature cycles. A comparison of digitized pulse shapes in the damaged and annealed detector indicates that the effect of extreme neutron damage (FWHM=6 keV) on the position resolution is on the order of ∼1.7 mm while for 3 keV resolution the position resolution degrades by ∼0.5 mm.