Sensitivity of GRETINA position resolution to hole mobility

The sensitivity of the position resolution of the gamma-ray tracking array GRETINA to the hole charge-carrier mobility parameter is investigated. The χ2 results from a fit of averaged signal (“superpulse”) data exhibit a shallow minimum for hole mobilities 15% lower than the currently adopted values. Calibration data on position resolution is analyzed, together with simulations that isolate the hole mobility dependence of signal decomposition from other effects such as electronics cross-talk. The results effectively exclude hole mobility as a dominant parameter for improving the position resolution for reconstruction of gamma-ray interaction points in GRETINA.