Two-dimensional detector arrays for hyperspectral x-ray imaging

Direct-conversion, position-sensitive x-ray detectors are needed in many important technologies such as medical and industrial imaging, nondestructive inspection (NDI) and evaluation (NDE), munitions monitoring, and baggage scanning. Advanced x-ray imagingtechniques can register both shape and spectral information by measuring the attenuation of multi-energetic x-rays through the imaged specimen. The density and composition data thus acquired can enable machine recognition of materials, a capability thatwould be useful for several military and industrial applications. Cadmium Zinc Telluride (CZT) has emerged as the detector material of choice forhyperspectral imaging because it works at room temperature with excellent energy resolution and has a large atomic number, which is essential for high-sensitivity detection of x-rays. High count rate uniformity and maxima of two million or more counts perpixel per second have recently been achieved in CZT using a new lineararray design and a custom readout system for ultra-fast hyperspectral line scanning. Further innovation building upon these developments would be desirable, in particular by designing and fabricating a high-throughput hyperspectral imaging system operatingin the alternative staring-array imaging mode which would be useful in static as well as conveyor-belt type inspection applications. A very concrete need presently exists for such a system in the manufacture of munitions, specifically in inspection andprocess control operations which cannot be adequately monitored using currenttechnologies. In response to this, we propose to develop a new x-ray radiographic system consisting of a monolithic two-dimensional, submillimeter resolution pixilated array CZT detector and the corresponding custom readout ASIC (Application SpecificIntegrated Circuit) and support electronics, which would have multiple x-ray energy imaging and high counting rate capability.The result of the proposed work will be a large, pixilated high-throughput, high-accuracy room-temperature and polarization freehyperspectral 2D x-ray imaging detector system with a custom made monolithic readout electronics chip to handle large amounts of data in real time. It will be able to perform hyperspectral, staring-array imaging in milliseconds using high flux output x-raygenerators. This detector has many application capabilities for both the military and commercial sectors, such as immediate discernment of material composition for defects and anomalies at production rates in all kinds of products including propellantsand explosives, as well as identifying material in security screening applications and medical imaging such as fast response bone densitometry. DoD applications include all standard x-ray and gamma ray inspection techniques at high speeds withhyperspectral imaging capability which is just evolving. For example, some of the applications are: NDI of munitions, Compton detectors for detection and monitoring ofradioactive material, inspection of containers, and contraband detection. CdZnTe detector can be especially useful in battlefields due to their compact nature and room temperature operation especially for radioactivity detection and imaging. Non-DoDapplications are even more extensive given the wider variety of objects requiring inspection in many different types of industrial situations. Our work will give special attention to the munitions inspection application which has specific and criticalprocess control needs.