Amorphous Selenium based X-ray Detector
Photo imaging is one of the most powerful and widely used tools for information acquisition, which is now extended to x-ray and covers various fields such as medical radiography, non-destructive inspection and astronomic observation. Enhancement in sensitivity enables acquisition of precise images under low light intensity, however, high sensitivity photodetectors such as photomultipliers and avalanche photodiodes (APD) sacrifice either spatial resolution or response speed that are both necessary for real-time imaging.
Amorphous-selenium (a-Se) based photodetectors are promising candidate for high sensitivity photo imaging devices, due to their high spatial resolution and response speed, as well as extremely high sensitivity enhanced by an internal carrier multiplication. HARP (high-gain avalanche rushing photoconductor) is the first a-Se based photodetector, which exploited the carrier multiplication and achieved effective quantum efficiency of 10 with real-time imaging capability.
In this Project, we will attempt to apply signal multiplication to a photodetector that consists of a-Se photoconductor and diamond cold cathode. A diamond cold cathode is a promising candidate to solve current problems of FEA-HARP (field emitter array-HARP). With a negative electron affinity surface and high thermal conductivity, diamond emitters should supply sufficient emission current to provide wide dynamic range. Furthermore, electron beam from diamond cold cathode has small dispersion angle due to its geometrical flexibility, which can prevent a resolution loss at the emitter.