Development of X-ray/gamma-ray imaging system based on hydrogenated amorphous silicon/crystalline silicon heterojunction strip detector

A high-energy X-ray/gamma-ray imaging system based on a hydrogenated amorphous silicon (a-Si : H)/crystalline silicon (c-Si) heterojunction strip detector was developed. The imaging system will be applied in nondestructive testing of concrete structures. We fabricated 50-channel heterojunction strip detectors with a 1 mm pitch on 500 μm thick p-type silicon wafers. The average leakage current was 2.9 nA per channel at 120 V reverse bias. Energy resolutions of 2.8 keV FWHM at 59.5 keV and 2.9 keV FWHM at 122 keV were obtained at 18degC. The position sensitivity of the strip detector was measured by edge-on irradiation with a ¹³⁷Cs gamma-ray source. Edge-on gamma-ray imaging of a tungsten object using the prototype was performed. A module consisting of 20 stacked silicon strip detectors is being constructed. (author)