Simple Technique for the Ultrapurification of Helium

Purer, A.; Stroud, Lowell; Meyer, T. O.

doi:10.1007/978-1-4684-3108-7_48

Cited by 3 publications

(2 citation statements)

References 5 publications

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“…A comparison of resonant frequencies with and without cold trap is shown in figure 8. The relative frequency shift (0.5 ppb ± 0.5 ppb), compatible with zero, confirms the assumption that the gas quality is indistinguishable in both cases, as in Pitre et al [25] and Purer et al [41]. The good agreement with and without cold trap proves that the concentrations of hydrogen and neon can be safely neglected.…”

Section: Gas Handling and Pressure Measurementsupporting

confidence: 81%

Measurement of thermodynamic temperature between 5 K and 24.5 K with single-pressure refractive-index gas thermometry

et al. 2020

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We describe measurements of thermodynamic temperature in the range 5 K to 24.5561 K (the triple point of neon) using single-pressure refractive-index gas thermometry (SPRIGT) with 4He. In the wake of the May 2019 re-definition of the kelvin and its associated mise en pratique, the main purpose of the work is to provide values of T–T 90, the discrepancy between thermodynamic temperature and that of the International Temperature Scale of 1990 (ITS-90). The link to ITS-90 is made via calibrated rhodium-iron resistance thermometers. Innovations required to reach the level of accuracy required for meaningful measurements (uncertainty in T–T 90 less than the expected deviation) include the suppression of temperature oscillations in a cryogen-free cryostat, a pressure stabilization scheme based on a non-rotating piston balance, modelling of the hydrostatic head correction and refinements of the measurement of microwave resonances in a quasi-spherical copper resonator. The accuracy of measurements varies from 0.05 mK to 0.17 mK and is competitive with that of all previous ones in this temperature range using other techniques. The improvement stems partly from the new techniques used for the new definition of the kelvin as well as ab initio calculations of the thermophysical properties ofgaseous 4He. In addition to confirming the validity of SPRIGT as an accurate, easier-to-implement alternative to other low-temperature primary thermometry techniques (e.g. acoustic gas thermometry) yet with scope for improvement, the results should provide important input data for any future revision of ITS-90.

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Section: Gas Handling and Pressure Measurementsupporting

confidence: 81%

Measurement of thermodynamic temperature between 5 K and 24.5 K with single-pressure refractive-index gas thermometry

et al. 2020

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“…However, in a previous publication [10], we compared the present cold trap (a simple cylinder of volume 4 cm 3 directly in contact with the liquid helium at 4 K) to a second cold trap, of volume 10 cm 3 and filled with charcoal that had a much larger surface at 4 K. Averaged over several hours, the square of the speed of sound in the helium gas delivered by the two cold traps differed by no more than 0.03 parts in 10 6 , demonstrating the equivalence of the two cold traps. Others have shown [22] that charcoal-filled cold traps reduced the neon concentration in helium to 210 9 , even when the traps were at much higher temperature, near 35 K. Finally, we note that Gavioso et al [14] had three samples of commercially purified helium analyzed for neon; the largest mole fraction that they reported was xneon = (0.07 ± 0.02) µmol mol 1 .…”

Section: Cold Trap Effectivenessmentioning

confidence: 56%

New measurement of the Boltzmann constantkby acoustic thermometry of helium-4 gas

et al. 2017

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The SI unit of temperature will soon be redefined in terms of a fixed value of the Boltzmann constant k derived from an ensemble of measurements worldwide. We report on a new determination of k using acoustic thermometry of helium-4 gas in a 3 l volume quasi-spherical resonator. The method is based on the accurate determination of acoustic and microwave resonances to measure the speed of sound at different pressures. We find for the universal gas constant R=8.3144614 (50) J•mol -1 •K -1 . Using the current best available value of the Avogadro constant, we obtain k=1.38064878(83)×10 -23 J•K -1 with u(k) /k = 0.60x10 -6 , where the uncertainty u is one standard uncertainty corresponding to a 68 % confidence level. This value is consistent with our previous determinations and with that of the 2014 CODATA adjustment of the fundamental constants (Mohr et al., Rev. Mod. Phys. 88, 035009 (2016)), within the standard uncertainties. We combined the present values of k and u(k) with earlier values that were measured at LNE. Assuming the maximum possible correlations between the measurements, (kpresent/〈k〉 − 1) = 0.07 × 10 −6 and the combined ur(k) is reduced to 0.56 × 10 −6 . Assuming minimum correlations, (kpresent/〈k〉 − 1) = 0.10 × 10 −6 and the combined ur(k) is reduced to 0.48 × 10 −6 .

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Removal of Impurities from Gases to be Processed at Low Temperatures

Dodge

1972

Advances in Cryogenic Engineering

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Simple Technique for the Ultrapurification of Helium

Cited by 3 publications

References 5 publications

Measurement of thermodynamic temperature between 5 K and 24.5 K with single-pressure refractive-index gas thermometry

Measurement of thermodynamic temperature between 5 K and 24.5 K with single-pressure refractive-index gas thermometry

New measurement of the Boltzmann constantkby acoustic thermometry of helium-4 gas

Removal of Impurities from Gases to be Processed at Low Temperatures

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