| 摘要 |
PURPOSE:To enable the measurement of uranium content with an ionization box of low background counts by evaporating a highly pure metal on a coat of synthetic resin applied on a current collection electrode and a protective electrode. CONSTITUTION:When neutron is irradiated on material 5 to be measured, uranium 235 contained in a sample as impurity undergoes a nuclear fussion and fussion fragments cause gas to be ionized in an ionization region 13. Ionized electrons induce voltage pulses in a current collection electrode 2 and the number of the pulses is counted to determined the content of the uranium in the sample. In this case, the current collection electride 2 and a protective electrode 12 are coated with a synthetic resin not containing nitrogen atom, on which a highly pure metal is evaporated to give an electric conductivity. This improves the uranium detection limit to about 0.1ppb for a trace uranium analysis ionization box having electrodes 12 and 2 in which an Al film (0.1mum) with a purity of 99.999% is evaporated on a acrylic film. |
