^Abstract:
The reduction of the dark current (DC) to a tolerable level in X-ray photoconductors is one of the key factors for their application as X-ray-to-charge transducers in the direct conversion flat panel X-ray imagers (FPXIs). Here, we discuss the origins of DC in an X-ray-to-charge transducer that is based on one of the most promising X-ray photoconductors: amorphous lead oxide (a-PbO). The transient DC in an a-PbO blocking structure is measured at different applied electric fields (5–20 V/μm). The experimental results are used to develop a theoretical model describing the electric field-dependent transient behavior of DC. We show that DC decay is caused by charge accumulation in deep localized states (traps) within the blocking layer. Accounting for the field-induced charge carrier release from traps, enhanced by charge hopping transitions, yields an excellent fit between the experimental and simulated results, thus clarifying the dynamic process of reaching a steady-state occupancy level of the deep localized states in the blocking layer. The model can be used to find an approximate optimal thickness of blocking layers for future iterations of a-PbO – based detectors without the need for time and labor-intensive experimental trial and error.

 

Thursday, November 10, 2022

10:30 a.m.

in CB 4058

 

1:30 PM in CB 4058

Abstract:
Albert Rose, the visionary at the Radio Corporation of America (first observed that image noise in television was due to the number of photons contributing to each image, and thus the image could be improved by increasing the quantum efficiency (of optical detectors (‘making every photon count’).  Our research on advanced technology for Positron Emission Tomography (detectors is based on this fundamental notion but also makes a step forward in ‘counting every photon’, meaning that instead of increasing the number of gamma photons used, we optimize the use of available radiation with the most sensitive PET detector.  This allows us to significantly decrease the radiation exposure associated with PET imaging and to minimize the potential damaging effects of excess radiation on human tissue.