DEVELOPMENT OF CDZNTE ENERGY SELECTIVE ARRAYS FOR INDUSTRIAL AND MEDICAL RADIATION IMAGING

Recent advances in the production of CdZnTe using the high pressure Br idgman growth process now make it possible to design and fabricate com plex X-ray sensor arrays on large monolithic substrates. These solid s tate ionization devices have the advantages of improved spatial and en ergy resolution, and produce significantly higher signals than competi tive scintillator-photodiode systems. We have fabricated a number of l inear and areal monolithic arrays in our laboratory using vacuum depos ited contacts on such material with good success. These arrays operate in a pulse counting mode using hybrid and surface mount circuitry mou nted in close proximity to the arrays. Linear devices with pitches of less than 0.8 mm and with 32 elements per substrate have been used for very wide dynamic range radioscopy with excellent results. Images are presented which demonstrate dynamic range in excess of 500:1 and Nyqu ist limited resolution at diagnostic X-ray energies for a wide variety of samples. Preliminary results demonstrate that the arrays can be us ed for energy selective radioscopy permitting the identification of di ffering materials within the image by approximate atomic number. Syste ms using areal arrays also have been evaluated as radiation cameras an d demonstrate good spatial and energy resolution. Examples of data tak en with a pin-hole collimator show the ability to distinguish source d istributions by energy as well as location and intensity. Ongoing work in the improvement of spatial and energy resolution and the fabricati on of larger arrays is discussed.