幸則 神田

He 集積法による中性子照射量測定のための He 絶対量測定装置

In the helium accumulation method for neutron dosimetry, it is applied that the number of helium atoms produced through (n,xα) reaction is proportional to neutron fluence in fast neutron irradiation fields. Besides, activities measuring in the activation method saturate to the value depending on their half-lives. A helium atom measurement, system for detecting of helium atoms accumulated in neutron-irradiated samples has been constructed and tested. The samples are vaporized in a furnace to release helium contained in them. The number of helium atoms is measured with a quadrupole mass spectrometer calibrated by a standard helium gas supply which is consist of a known-volume vessel, a pressure gauge and a thermometer. It has been proposed in this work that helium-ion implanted aluminum disks are applied to calibrate the helium atom measurement system. This method has succeeded to obtain results agreed with the standard helium gas supply system.

Ni 同位核からのサブ・クーロン障壁陽子の放出

A peak at low region of a proton spectrum in 14MeV-neutron-induced reactions is understood to be composed of sub-Coulomb-barrier protons. It is found by Grimes et al. in 14MeV-neutron experiments by an intense neutron source, Rotating Target Neutron Source-I. They predicted that the spectra calculated from the multi-step Hauser-Feshbach model agreed with the experimental ones. We have calculated in the same ways the proton spectra in the neutron-induced reactions for Ni isotopes near 10MeV. It has been concluded that the protons emitted by (n,np) reactions can be distinguished from the protons from the other reactions on the proton spectra if the incident neutron energies beyond about 3MeV from the threshold energy of the (n,np) reaction. The experiments are proposed and being made by Grimes expecting to check the reaction mechanism of emission of sub-Coulomb-barrier protons.