Sub-segment position measurement in 32-fold segmented high-purity germanium detectors

Sub-segment position resolution of gamma-ray interactions has been demonstrated for the cylindrically-symmetric 32-fold segmented HPGe detectors of the NSCL/MSU Segmented Germanium Array (SeGA) using digital electronics. Flash ADCs sampled waveforms at 100 MHz to measure both real and induced charges from the outer contact segments of a SeGA detector. To bypass issues with computation and bandwidth, integral quantities based on short (1-2 $\mu $sec) waveform samples were used. Analysis of induced charges on segments neighboring those with real charge deposition allowed for sub-segment position resolution along both the crystal's linear axis and the azimuthal angle. Multiple measures of the real charge signal's rise time allowed for determination of the radial position.