Patent ID: 7141795

Claim:
A radioactivity measuring apparatus using an optical fiber, said apparatus comprising: an elongated plate-shaped radioactivity detection section provided with a scintillator; a radioactivity measuring section provided with a photomultiplier and arranged separately from said radioactivity detection section; and a wavelength conversion optical fiber cable connected between said radioactivity detection section and said radioactivity measuring section, wherein a measurement signal of α-rays detected by said radioactivity detection section is transmitted to said radioactivity measuring section via said optical fiber cable, wherein said radioactivity detection section comprises a plurality of elongated light guides; a plurality of sets of wavelength conversion optical fibers, each set consisting of two fibers, arranged along said light guides in close contact therewith, said optical fibers extending from said radioactivity detection section as the wavelength conversion optical fiber cable provided with a light-shielding outer covering; a scintillator layer located on the surface of said light guide; a light-shielding film disposed so as to cover said scintillator layer; and a light-shielding frame having an elongated frame structure and surrounding said light guides, said optical fibers, said scintillator layer and said light-shielding film so that only a detection surface of said light-shielding film is exposed.