| 摘要 |
PURPOSE:To enhance geometrical efficiency without increasing the counting rate of background and to achieve the compact configuration and a high sensitivity of a detector by bundling scintillation optical fibers in parallel, and bringing the optical fibers into close contact with the inner wall of a tank in a tubular shape. CONSTITUTION:Scintillation optical fibers 1 are bundled in parallel at the inner side of a gas sampling tank 2. A shading film 3 covers the surrounding part of the tank 2. A photomultiplier 4 is arranged at one end of the optical fiber 1. The optical fiber 1 comprises a core comprising a scintillator and a clad, whose refractive index is smaller than that of the core. When radiation such as beta rays enters, the scintillation light is emitted from the scintillator of the core. Therefore, when radioactive gas is introduced into the tank 2, the radiation cast on the side wall of the tank 2 causes the mutual reaction with the optical fiber, and the scintillation light is emitted. The scintillation light is effectively guided to both ends of the optical fiber 1 because the refractive index of the core is larger than the refractive index of the clad and detected with the photomultiplier 4.
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