Effect of Number of Readout Channels on the Performance of a Continuous Miniature Crystal Element (cMiCE) Detector

In this work we investigate how the intrinsic spatial resolution varies with the number of digitized readout channels for a 64 (8 times 8) channel detector using a statistics-based positioning algorithm. We report results for both 6 mm and 8 mm thick crystals. Three channel reduction schemes are explored. The simplest scheme is row and column summing (R-C sum) of the PMT channels. The second method is to only use channels with signals above a 1% threshold of the total signal (1% thres). The third method is to acquire a subset of PMT channels determined by the maximum signal channel (zone mask). The full width at half maximum (FWHM) intrinsic spatial resolution results for the central and corner sections of the detector are presented for each of the methods. All methods except R-C sum performed well for the central section of the detector. The 1% thres and zone mask schemes showed significant improvement for the corner section of the 6 mm thick crystal. All methods using a single depth LUT had difficulty in the corner region for the 8 mm thick crystal. We believe this is caused by depth dependent edge effects on the light response function. Initial results using a depth dependent look-up table show improved positioning performance.