A new all-metal induction furnace for noble gas extraction

Abstract

A new all-metal induction furnace for extraction of all noble gases from pyroxenes, olivines, quartz or barites has been developed at CRPG. It differs in design from other induction furnaces in that the totality of the vacuum vessel is metallic and the induction coil, normally located outside the furnace, has been placed inside the vacuum vessel, with a special radio frequency power feedthrough welded onto a flange. The volume of the crucible is ≈ 15 cm^3 and permits fusion of samples with a mass of up to 1 g. Samples are packed into a metal foil, loaded into a carousel, baked out before analysis, and then sequentially dropped into the Ta-crucible. The low weight of the crucible (≈ 120 g) allows for short and efficient degassing cycles. When the furnace is pumped for the first time after samples loading, short cycles between 500 and 1800 °C at fast heating rates (≈ 400 °C·min^(−1)) are sufficient to achieve very low blanks. The durations of these cycles are range from 30 min for He to up to a few hours for Ne, Kr and Xe. Blanks of He, Kr and Xe (10 min heating durations) and Ne (20 min) in static vacuum are (1.6 ± 1.0) × 10^(−15) mol ^4He (T = 1750 °C), (5.8 ± 2.3) × 10^(−17) mol ^(20)Ne (T = 1500 °C), (2.1 ± 0.3) × 10^(−18) mol ^(84)Kr (T = 1700 °C) and (4.4 ± 0.4) × 10^(−18) mol ^(132)Xe (T = 1700 °C). Argon blanks have not yet been measured.

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