Accurate Determination of the Absolute 3He/4He Ratio of a Synthesized Helium Standard Gas (Helium Standard of Japan, HESJ): Toward 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 interlaboratory 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. 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.

Original languageEnglish
Pages (from-to)3995-4005
Number of pages11
JournalGeochemistry, Geophysics, Geosystems
Volume19
Issue number10
DOIs
Publication statusPublished - Oct 2018

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All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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