Characterizing and correcting the cross-talk effect on depth measurement in the NCT detectors

The Nuclear Compton Telescope (NCT) is a balloonborne soft gamma ray (0.2-10 MeV) telescope designed to study astrophysical sources of nuclear line emission and polarization. The heart of NCT is an array of 12 cross-strip germanium detectors, designed to provide 3D positions for each photon interaction with full 3D position resolution to 1.6 [mm.sup.3]. The x and y positions are provided by the orthogonal strips, and the interaction depth (z position) in the detector is measured to an accuracy of 0.4 mm FWHM using the relative timing of the anode and cathode charge collection signals. The charge collection signals are affected by cross-talk when interactions occur in adjacent strips, altering the timing measurement in those interactions. We simulated this effect in our NCT detectors, and have developed a method to correct the timing information. Here we present the simulation and the correction results. Index Terms--Compton telescope, gamma-ray astronomy detectors, germanium radiation detectors.