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| Construction on Graphite Cavity Ionization Chamber as Air Kerma Primary Standard for 137Cs γ Rays |
| LI De-hong1,WANG Pei-wei1,WU Meng-meng1,2,CHENG Jian-bo1,3,GUO Bin1 |
1. National Institute of Metrology, Beijing 100029, China
2. China Institute of Atom Energy, Beijing 102413, China;
3. Lanzhou University, Lanzhou, Gansu 730000, China |
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Abstract A cylindrical graphite cavity ionization chamber is designed and constructed according to Bragg-Gray theory, which is used for the establishment for primary standard for cesium-137 γ Rays. Ground protection structural of the ionization chamber wall and the collector is optimized through theoretical calculations of the electric field distribution of sensitive volume of the ionization chamber. And the results of a series of tests including the saturation curve, the background current and the stability show that the design fully meet the requirements. The air kerma of the cesium-137 sources is directly realized using the graphite cavity ionization chamber whose correction factors are got though theoretical calculations and experimental measurements. At last, the combined standard uncertainty of air kerma measurement is 0.25％.
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Received: 24 November 2014
Published: 22 March 2016
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2016, Vol. 37 
