We report the development of a CdZnTe gamma ray imager whose advantages over the conventional Anger camera include 1) improved contrast resulting from superior energy resolution and unambiguous position determination and 2) the small size and weight and high reliability inherent in an all-solid-state construction. It provides high energy resolution and peak efficiency by incorporating Digirad's new SpectrumPlusTM detector technology. The new imager employs a modular design, in which each 1" x 1" module incorporates a monolithic 64-element CdZnTe detector array and ASIC-based circuity that provides signal conditioning for every channel, identification of valid events and addressing fimctions. Imagers with a wide range of sizes and shapes can be assembled by tiling modules together on a specially designed signal routing board.
Single-crystal CdS can be converted by cation exchange in CuCl solution to single-crystal copper sulfide with the chalcocite, djurletie, and CuxS (with 1.96>x>1.8) structures. The last is a previously undescribed hexagonal or pseudohexagonal phase with a=15.475±0.010 Å and c=13.356±0.010 Å. The structural relationship of the various phases to each other and to CdS is described with reference to two basic sulfur arrangements: hexagonal and cubic close packing. The gradual shift of phase of small crystals from high to lowered copper content is attributed to surface oxidation of copper atoms and strongly suggests that natural chalcocite crystals may also change composition and phase with time.
Previous work has shown that hybrid semiconductor detector arrays similar to those used in infrared focal-plane arrays are very attractive for use in nuclear medicine and other gamma-ray imaging applications. In this paper, we describe the development of a 64 • 64 readout multiplexer specifically for use in gammaray imaging; we also describe the construction of 64 • 64 CdZnTe hybrid detector arrays using the new readout. The readout and detector array are both about one inch square (2.5 cm • 2.5 cm) and have 380 pm pixel pitch. Some initial assembly problems have been resolved by stabilizing the hybrids with epoxy. Preliminary testing results are presented that verify that the 64 • 64 CdZnTe arrays perform as excellent imaging spectrometers:
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