| 摘要 |
PURPOSE:To prevent expelling of electrons by gamma rays, by using a low atomic number element such as a plastic for shell, BF3 for a neutron detector, and a molecular sheave carbon for an impure gas trap. CONSTITUTION:As a cathode 2, a thin body is used to reduce expelling of electrons by gamma rays and prevent a gamma ray pileup phenomenon, and, a deterioration of pressure resistance owing to the thin cathode body is covered by an outer wall 3 which is made of a low atomic number element such as a plastic. The incident neutrons 14 pass through the outer wall 3 and the cathode 2, made the (n, alpha) reaction with boron in BF3 gas which is the neutron detecting gas 4 in pipes 6, and the energy of Q value of the reaction is detected. On the other hand, alpha rays 15 which penetrate the outer wall 3 and the cathode 2 dissociate the BF3 to produce F2, which should be removed because it is nonconductive and disturbs the measurement. As an absorbent 9 in an impure gas trap 8, a molecular sheave carbon is used. In such a composition, expelling of electrons by gamma rays can be prevented.
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