Timing methods for depth determination in germanium strip detectors

Abstract

The ability to measure the interaction depth of a gamma ray in a planar germanium strip detector has been demonstrated using various Constant Fraction Discriminators (CFD) and leading edge discriminators. Thick detectors can then be used in Compton telescopes or other detectors that require three-dimensional position resolution. Large systems based on these detectors require many thousands of channels of electronics which necessitates a move to CMOS ASIC readout. Traditional CFDs do not lend themselves to CMOS due to their need for delay lines. Different timing methods better suited for CMOS include leading edge discriminators and falling edge discriminators. The simplest methods seem to work well in the laboratory and indicate that CMOS electronics can be built to read out a thick strip detector with depth resolution. This technique is suitable for a variety of semiconductor detectors.