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arXiv · 1804.08048

Accurate determination of the absolute 3He/4He ratio of a synthesized helium standard gas (Helium Standard of Japan, HESJ): Towards revision of the atmospheric 3He/4He ratio

Kenji Mishima·Hirochika Sumino·Takahito Yamada·Sei Ieki·Naoki Nagakura·Hidetoshi Otono·Hideyuki Oide
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Abstract

The helium standard of Japan, referred to as HESJ, is an inter-laboratory standard for the 3He/4He ratio. While the ratio of 3He and 4He of the HESJ was previously determined by a relative comparison to atmospheric helium, the absolute value of the 3He/4He ratio of the HESJ has not been directly determined yet. Therefore, it relies on the early measurements of that of atmospheric helium. The accuracy of the absolute 3He/4He ratios of the atmosphere and other working standards including HESJ is crucial in some applications of helium isotopes, such as tritium-3He dating, surface-exposure age determination based on cosmogenic 3He, and the accurate measurement of the neutron lifetime. In this work, new control samples of helium gases with 3He/4He ratios of 14, 28, and 42 ppm were fabricated with accuracy of 0.25-0.38% using a gas-handling system for a neutron lifetime experiment at Japan Proton Accelerator Research Complex (J-PARC). The relative 3He/4He ratios of these samples and the HESJ were measured using a magnetic-sector-type, single-focusing, noble gas mass spectrometer with a double collector system. As a result, the absolute 3He/4He ratio of the HESJ was determined as 27.36 +/- 0.11 ppm. The atmospheric 3He/4He ratio was determined as 1.340 +/- 0.006 ppm, based on this work.

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Kenji Mishima, Hirochika Sumino, Takahito Yamada, Sei Ieki, Naoki Nagakura, Hidetoshi Otono, Hideyuki Oide. 2018-04-22. Accurate determination of the absolute 3He/4He ratio of a synthesized helium standard gas (Helium Standard of Japan, HESJ): Towards revision of the atmospheric 3He/4He ratio. https://doi.org/10.1029/2018gc007554

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