Basic study on the development of low exposure CT with Frisch grid avalanche diode. JAERI's nuclear research promotion program, H13-011 (Contract research)

For the development of low exposure CT, we have conducted a basic study on Frisch grid avalanche diode detector to realize a high efficiency, high counting rate X-ray detector. First, we fabricated Frisch grid Si detector made of one crystal and studied their features. For the development of X-ray detector with higher performance, bonding semiconductor wafers, including different semiconductors, such as Si and CdTe, is necessary. We have bonded Si wafers by surface activation method and studied on the electric performance of bonded Si wafers. The current-voltage curve of bonded pn Si wafers showed rectifying characteristics, although Si pn junctions are made by diffusion method, generally. Second, we proposed a low dose exposure X-ray transmission method using filtered X-ray and energy subtraction method. The dose exposure with this method is estimated as low as 30% of that of using white X-rays. If we compare the dose exposure of conventional current measurement method, we would conclude further advantage of this method. With the combination of low dose exposure X-ray transmission method and the Frisch grid detector, high performance X-ray transmission method and low exposure CT system will be developed in future. (author)