Radiation detector

The present invention concerns an improvement of a radiation detector used for a radiation ray medical diagnosing device such as, an X-ray tomographic device (X ray CT) and a positron computed tomographic device (position CT), and for high energy physics. That is, studies are made on a relation between the surface state of crystals and the amount of light emission by using Bi4Ge3O12 crystals (BGO crystal) used for the positron CT, to obtain a radiation detector which emits a great amount of scintillation light and has a high transfer efficiency to photomultipliers. More specificatlly, BGO crystals roughened at the surface opposing to the scintillation light emission surface and mirror-polished at other surfaces are used. It is preferred that the surface roughned of the roughned surface is at leasr 0.8μm. further, it is preferred that a reflecting layer is disposed to the surfaces other than the roughned surface and the scintilltion light emission surface. (I.S.)