Papers by Author: Sung Il Choi

Abstract: In this study, we designed a flat-panel digital X-ray imaging module based upon the amorphous silicon (a-Si) technology and tested potential for medical imaging and nondestructive testing. The module employs a commercially available a-Si photosensor array of a 143 μm x 143 μm pixel size and a 42.9 cm x 42.9 cm active area, coupled with a CsI(Tl) scintillator of a 550 μm thickness, and a readout IC board which can be accessed through our home made GUI software. The experimental test was performed to evaluate the system response with exposure, modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE).

Abstract: The gas electron multiplier (GEM), placed in the drift volume of a conventional gas detector, is a conceptually simple device for producing a large gas gain by concentrating the drift electric field over a very short distance to the point that electron avalanching occurs. This device consists of a thin insulating foil of several tens of μm in thickness, covered on each side with a thin metal layer, with tiny holes, usually 100 μm or less in diameter, and with a spacing of 100-200 μm through the entire foil, perforated by using chemical etching or high-powered laser beam technique. In this study, we have investigated its operating properties with various experimental conditions and demonstrated the possibility of using this device as a digital X-ray imaging sensor, by acquiring X-ray images based upon the scintillation lights of the GEM with a standard CCD camera.