Spire proposes to develop advanced detector arrays for X-ray computed tomography by monolithically integrating CdTe photodiodes on scintillators. Due to reduced optical loss at the photodiode/scintillator interface and a better spectral match to the scintillator emission wavelength, this new detector promises improved signal compared to X-ray detectors using mechanically-stacked silicon-on-scintillator photodiodes. In addition, the cost of CdTe detectors will be substantially lower because we will use low-cost, thin-film, manufacturing technology and will reduce assembly complexity by obviating the need for precise stacking of photodiodes on the scintillators. In Phase I, we demonstrated single element integrated X-ray detectors with improved performance over conventional Si photodiodes. High sensitivity X- ray detectors were fabricated by (a) gluing CdTe-photodiodes-on-glass to a CdWO4 scintillator, and (b) depositing CdTe photodiodes directly on CdWO4 by thermal evaporation. In both cases, the CdTe photodiode exhibited higher responsivity in the 500 to 800 nm range, than currently-used Si photodiodes. X-ray detectors fabricated from these photodiodes showed better performance than mechanically- stacked Si photodiode-on- scintillator X-ray detectors. Advancing the single element technology whose feasibility was shown in Phase I to a demonstration of commercially viable arrays is the objective of Phase II. To achieve this objective, detector performance will be further advanced, first by perfecting the processes employed to fabricate single-element detectors, then by marrying these processes with the optimized design to construct a new class of greatly improved detectors. Spire will produce monolithically integrated arrays suitable for tomography, and work closely with XCT manufacturers and users to assure that the array meets their needs and can be integrated into their products.
X-ray detectors with enhanced signal and low-cost will find applications in computed tomography system for imaging the human body and large organs. In addition, these devices would be useful in airport baggage X-ray systems, in flash X-ray (stop-action imaging), rapid scanning, portable radioisotope detection system for nuclear wasted process monitoring, and high background applications.
