<title>Application of monolithic CdZnTe linear solid state ionization detectors for x-ray imaging</title>

Current approaches to digital radiography and tomography are dominated by the use of Scintillator-Photodiode arrays as detectors. To improve the quality of the data for such measurements it is desirable to increase the efficiency of the device both for the absorption of incoming x rays as well as the ratio of current produced per unit dose. In order to be of practical use, such detectors must maintain a high signal to noise performance and level of dark current stability in the presence of large radiation fluxes. In this laboratory, we are exploring the use of monolithic linear arrays that directly convert ionizing radiation into charge without the intervening photo-emission step. We have evaluated detectors made from CdTe as well as CdZnTe intrinsic material with a variety of contact methods. Our studies have shown that the relative efficiency of charge collection of the holes within the pulse shaping time is the most significant parameter governing their use. Data have been collected on this property from several devices. CdZnTe solid state devices produce over ten times the current per absorbed dose than a typical scintillator-photodiode. Recent advances in raw material production and contact technology provide detectors which can maintain their operating characteristics over kilo-rad of dose. Readout methods that use pulse counting mode operation have been evaluated. Results are shown on the sensitivity and spatial resolution of these detectors. Examples of results taken with multi-element, monolithic devices fabricated thus far are demonstrated with some estimates on the possibility for the production of larger arrays.