| 摘要 |
PURPOSE:To exactly measure a radiation density extending from a low density to a high density by making a ratio of a sensitive part area of both measuring sensitive parts to be used, and a detection sensitivity different from each other, and also forming both the measuring sensitive parts by using the same material. CONSTITUTION:When a prescribed measuring gas 100 is supplied to each ionization chamber 12, 14 through a feed pipe 10, an ionization is caused at the same ionization degree by a radioactive substance contained in the measuring gas 100, in the ionization chambers 12, 14. At the same time, a radioactivity due to adhesion, diffusion, etc., of the radioactive substance is generated in the inside of each ionization chamber 12, 14. However, as for the ionization chambers 12, 14, its inner areas Ssp, Ssl are formed to an equal value, therefore, the total radioactivity contamination quantity in these ionization chambers 12, 14 becomes roughly equal. Accordingly, by such a radioactivity contamination substance, the ionization quantity generated in the inside of the ionization chambers 12, 14 becomes equal, and from a current collecting electrode 18, an ion which has been generated by its ionization is collected, and from a current collecting electrode 20, an electron which has been generated by its ionization is collected. Accordingly, by an addition processing, a radiation density can be measured exactly.
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