PTB-96: The Ultra-Low Temperature Scale of PTB

Fellmuth, B.; Hechtfischer, D.; Hoffmann, Albrecht

doi:10.1063/1.1627103

Cited by 8 publications

(11 citation statements)

References 2 publications

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“…The dissipation ( Q −1 ) was calculated by relating the observed amplitude at resonance to the drive voltage (after calibration at a fixed drive). Temperatures were measured using a melting curve thermometer 51 52 and then related to the frequency shift and dissipation of a quartz fork, immersed in the same heat exchanger as the 3 He in the torsion pendulum 53 . Below we express temperatures in units of the bulk T c , measured in situ by the fork.…”

Section: Resultsmentioning

confidence: 99%

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The A-B transition in superfluid helium-3 under confinement in a thin slab geometry

Zhelev¹,

Abhilash²,

Smith³

et al. 2017

Nat Commun

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The influence of confinement on the phases of superfluid helium-3 is studied using the torsional pendulum method. We focus on the transition between the A and B phases, where the A phase is stabilized by confinement and a spatially modulated stripe phase is predicted at the A–B phase boundary. Here we discuss results from superfluid helium-3 contained in a single 1.08-μm-thick nanofluidic cavity incorporated into a high-precision torsion pendulum, and map the phase diagram between 0.1 and 5.6 bar. We observe only small supercooling of the A phase, in comparison to bulk or when confined in aerogel, with evidence for a non-monotonic pressure dependence. This suggests that an intrinsic B-phase nucleation mechanism operates under confinement. Both the phase diagram and the relative superfluid fraction of the A and B phases, show that strong coupling is present at all pressures, with implications for the stability of the stripe phase.

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Section: Resultsmentioning

confidence: 99%

“…Temperatures were measured using a melting curve thermometer 52,53 and then related to the frequency shift and dissipation of a quartz fork, immersed in the same heat exchanger as the 3 He in the torsion pendulum. 54 Below we express temperatures in units of the bulk Tc, measured in situ by the fork.…”

Section: Measurablesmentioning

confidence: 99%

The A-B transition in superfluid helium-3 under confinement in a thin slab geometry

Zhelev¹,

Abhilash²,

Smith³

et al. 2017

Nat Commun

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“…Soulen et al used the thermometer to establish a temperature scale between 6 mK and 740 mK with an accuracy of about 0.1% [92,95]. Fellmuth and Schuster et al also built an R-SQUID thermometer to establish a scale below 0.6 K [96,97]. R-SQUID noise thermometers have largely been replaced by current-sensing noise thermometers since the mid-1990s due to much reduced measurement times and the increasing availability of low-cost SQUIDs.…”

Section: Josephson or R-squid Thermometermentioning

confidence: 99%

Johnson noise thermometry

Benz

Rogalla

et al. 2019

Meas. Sci. Technol.

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Johnson noise thermometers infer thermodynamic temperature from measurements of the thermally-induced current fluctuations that occur in all electrical conductors. This paper reviews the status of Johnson noise thermometry and its prospects for both metrological measurements and for practical applications in industry. The review begins with a brief description of the foundations and principles of Johnson noise thermometry before outlining the many different techniques and technological breakthroughs that have enabled the application of Johnson noise thermometry to high-accuracy, cryogenic, and industrial thermometry. Finally, the future of noise thermometry is considered. As the only purely electronic approach to thermodynamic temperature measurement, Johnson noise thermometry has appeal for metrological applications at temperatures ranging from below 1 mK up to 800 K. With the rapid advances in digital technologies, there are also expectations that noise thermometry will become a practical option for some industrial applications, perhaps reaching temperatures above 2000 K.

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“…In 2002, as part of an international comparison, Hill at NRC [12] reported results for ITS-90 below 4.2 K. In 2003 Shimazaki and Tamura at NMIJ/AIST [13] implemented ITS-90 between 0.65 K and 3 K before upgrading their apparatus to a cryogen-free system in 2011 [14]. In 2003, Engert and Fellmuth at PTB [15] reported extensive measurements of 3 He vapour pressure from 0.65 K to 1.2 K. Later, in 2007, using PLTS-2000 to estimate the thermodynamic inconsistency of ITS-90 below 1 K, Engert et al [16] established a new 3 He vapour pressure scale known as PTB-2006.…”

Section: Introductionmentioning

confidence: 99%

“…The PTB's results showed that the inconsistencies between them increase from 0.66 mK at 1 K to 1.51 mK at 0.65 K. Of the two scales, PLTS-2000 has a sounder thermodynamic basis and the potential for a lower uncertainty. For this reason, to establish a harmonious connection between them, it has been suggested that values of PLTS-2000 should be used to correct ITS-90 rather than the reverse [15,16]. To this end, PTB has carried out such a task, performing an indirect comparison in 2006 [16] in which two rhodium-iron resistance thermometers were used as transfer standards.…”

Section: Introductionmentioning

confidence: 99%

Direct comparison of ITS-90 and PLTS-2000 from 0.65 K to 1 K at LNE-CNAM

et al. 2021

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In the temperature range between 0.65 K and 1 K, the international temperature scale of 1990 (ITS-90) is based on 3He vapour–pressure thermometers and overlaps with the provisional low temperature scale of 2000 (PLTS-2000) defined by the melting pressure of 3He. An indirect comparison at PTB revealed differences between the two scales of up to 1.5 mK at 0.65 K (Engert et al 2007 Metrologia 44 40–52). Stimulated by the PTB results, we have performed a direct comparison T 90–T 2000 from 0.65 K to 1 K at LNE-CNAM. To test repeatability, the experiment was conducted twice: in 2019 and 2020. We find differences T 90–T 2000 of 0.28 mK at 1 K, increasing to 1.58 mK at 0.65 K. The direct comparison, eliminates the uncertainty component due to the transfer resistance thermometer and its calibration. Except for a point near 1 K, the new results are in accordance with those obtained at PTB (differences of less than 0.22 mK), which makes it possible to improve the accuracy of the equation specified in ITS-90.

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PTB-96: The Ultra-Low Temperature Scale of PTB

Cited by 8 publications

References 2 publications

The A-B transition in superfluid helium-3 under confinement in a thin slab geometry

The A-B transition in superfluid helium-3 under confinement in a thin slab geometry

Johnson noise thermometry

Direct comparison of ITS-90 and PLTS-2000 from 0.65 K to 1 K at LNE-CNAM

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