1 Position-sensitive CZT detector

Recent advances in CdZnTe (CZT) detector technology make gamma-ray burst localization possible using a coded mask imager consisting of a position sensitive CZT detector plane in conjunction with a coded mask. A prototype position-sensitive CZT detector (Fig. 1) that uses crossed-strip readout with 22 electrodes on each face has been developed (Matteson et al. 1998a). The strip pitch of 500$\mu$m yields $\rm 0.5\,mm \times \,0.5\,mm$ pixels. Each anode and cathode strip is separately read out by its own preamplifier and electronic chain, contained in one of two 32 channel ASICs from Nova R&D, Inc, called RENAs (Readout Electronics for Nuclear Applications), or in discrete electronics. Between the anode strips is a set of "steering electrodes'', which are biased negative relative to the anodes to produce a well-defined electric field in the gap between the anodes, which improves charge collection.

  

Figure 1: Prototype detector ($12\times 12\times 2$ mm3). Left: Anode side; steering electrodes can be seen between anode strips. Right: Detector installed in platform used in laboratory and balloon flight tests. Strip detector left of center (cathode side on top) and planar detector at far right