Patent ID: 7932499

Claim:
A radiation detector, comprising: a semiconductor photo-detecting element array having a plurality of semiconductor photo-detecting elements arranged lengthwise and breadth-wise on a plane; a plurality of scintillator elements arranged on the semiconductor photo-detecting element array to have bottoms of the scintillator elements each fixed to each of the plurality of semiconductor photo-detecting elements; a first light-reflecting material layer coating a top of each of the scintillator elements opposite to the bottom; second light-reflecting material layers composed of metal layers covering side surfaces of each of the scintillator elements; and a radiation shielding material layer composed of resin and particles of a heavy metal element blended in the resin, which radiation shielding material layer is filled between adjacent second light-reflecting material layers covering the side surfaces of the scintillator elements arranged to neighbor on each other, wherein the radiation shielding material layer consists essentially of 90 wt. % or more of the particles of a heavy metal element selected from Nb to Bi in the Periodic Table and the rest being resin, and wherein a region of the radiation shielding material layer, which interposes between two adjacent second light-reflecting material layers covering the side surfaces of the scintillator elements neighboring on each other, contains the particles of a heavy metal element that consist of at least three particles of a heavy metal element having diameters within +/−3 μm of a gap width between the two adjacent second light-reflecting material layers and the rest of the particles of a heavy metal element having diameters less than those of the at least three particles of a heavy metal element.