3D Corrections for Position-Sensitive Capacitive Frisch-Grid TlBr Detectors

This work evaluates data from position-sensitive capacitive Frisch-grid (PS-CFG) TlBr detectors for correcting the gamma-ray energy spectrum based on the location of the interaction in the crystal. This enables the correction of non-uniformity in the signal response. Signals from 5×5×12 mm ³ TlBr PS-CFG detectors generate anode amplitude versus cathode-to- anode-ratio histograms, which map the interaction depth for a 32×32 grid of XY pixels. The width of the 662-keV photopeak from ¹³⁷ Cs irradiation contains contributions from statistics and non-uniformity. The dependence of the signal on the interaction depth produces an asymmetric "tail" in the photopeak in the anode spectra. This work also evaluates the dependence of the non-uniformity corrections on long-term stability, while under constant 1500 V bias at room temperature after 3 and 5 months of operation. The 3D corrections compensate for some non-uniformity; however, the interaction location determined by the approach represents the centroid of the charge distribution. Variations in the sampling of non-uniformities produced by the shape of the charge distribution may not be corrected. We suspect that the current energy resolution may be limited by uncorrected non-uniformities.