Thermal boundary resistance between liquid helium and silver sinter at low temperatures

Voncken, A. P. J.; Riese, D.O.; Roobol, L. P.; König, Reinhard; Pobell, F.

doi:10.1007/bf00754629

Cited by 8 publications

(22 citation statements)

References 27 publications

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“…The estimated cell wall area is 0.12 m 2 giving us R 0,L = (0.17 ± 0.05) m 2 K p L +1 W −1 as the area-scaled constant R 0 = A∕r . The exponent p L is close to the theoretical value 3 from the acoustic mismatch model, while the prefactor R 0,L is about 1000 times larger than typically found in sintered heat exchangers [48].…”

Section: Plain Cell Wallsupporting

confidence: 78%

“…Oh et al [20] determined at 1 MPa that the Kapitza resistance between their sinter and saturated mixture followed exponent p = 2 with the coefficient R 0 between 10 and 30 m 2 K 3 W −1 depending on the magnetic field of their experiment. Voncken et al [48], on the other hand, measured the Kapitza resistance of saturated mixture and sinter in situation where the phase-separation boundary was within the sinter, receiving either p = 2 or 3, with R 0 = 6.5 m 2 K 3 W −1 or 0.0029 m 2 K 4 W −1 , respectively. The comparison is Fig.…”

Section: Sintermentioning

confidence: 99%

“…The dashed black lines show the behavior at the upper and lower end of the r V confidence bounds, while the red line is the low-temperature fit and blue the best r V to the current dataset with p V = 1.7 kept constant summarized in Table 2 which also includes the Kapitza resistances in 3 He -B from Refs. [48] and [49]. Our heat-exchanger volume is mostly filled by pure 3 He , but since there is 4 He readily available in the system, all available surfaces are covered by it.…”

Section: Sintermentioning

confidence: 99%

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Performance of Adiabatic Melting as a Method to Pursue the Lowest Possible Temperature in $$^{3}\hbox {He}$$ and $$^{3}\hbox {He}$$–$$^{4}\hbox {He}$$ Mixture at the $$^{4}\hbox {He}$$ Crystallization Pressure

2020

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We studied a novel cooling method, in which 3 He and 4 He are mixed at the 4 He crystallization pressure at temperatures below 0.5 mK. We describe the experimental setup in detail and present an analysis of its performance under varying isotope contents, temperatures, and operational modes. Further, we developed a computational model of the system, which was required to determine the lowest temperatures obtained, since our mechanical oscillator thermometers already became insensitive at the low end of the temperature range, extending down to (90 ± 20) μK ≈ T c (29±5) (T c of pure 3 He). We did not observe any indication of superfluidity of the 3 He component in the isotope mixture. The performance of the setup was limited by the background heat leak of the order of 30 pW at low melting rates, and by the heat leak caused by the flow of 4 He in the superleak line at high melting rates up to 500 μmol/s. The optimal mixing rate between 3 He and 4 He , with the heat leak taken into account, was found to be about 100..150 μmol/s. We suggest improvements to the experimental design to reduce the ultimate achievable temperature further.

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Section: Plain Cell Wallsupporting

confidence: 78%

Section: Sintermentioning

confidence: 99%

Section: Sintermentioning

confidence: 99%

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Performance of Adiabatic Melting as a Method to Pursue the Lowest Possible Temperature in $$^{3}\hbox {He}$$ and $$^{3}\hbox {He}$$–$$^{4}\hbox {He}$$ Mixture at the $$^{4}\hbox {He}$$ Crystallization Pressure

2020

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“…To achieve similar cooling power with an external cooling method, the surface area of the helium cell would have to be of order 10 000 m 2 , which was estimated using the thermal boundary resistance values from Ref. [30]. Such large surface areas are hard to obtain in practice, as it would require several kilograms of sintered silver powder layered on the cell surfaces.…”

Section: Cooling Powermentioning

confidence: 99%

Thermodynamics of adiabatic melting of solid He4 in liquid He3

2019

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In the cooling concept by adiabatic melting, solid 4 He is converted to liquid and mixed with 3 He to produce cooling power directly in the liquid phase. This method overcomes the thermal boundary resistance that conventionally limits the lowest available temperatures in the helium fluids and hence makes it possible to reach for the temperatures significantly below 100 μK. In this paper we focus on the thermodynamics of the melting process, and examine the factors affecting the lowest temperatures achievable. We show that the amount of 3 He− 4 He mixture in the initial state, before the melting, can substantially lift the final temperature, as its normal Fermi fluid entropy will remain relatively large compared to the entropy of superfluid 3 He. We present the collection of formulas and parameters to work out the thermodynamics of the process at very low temperatures, study the heat capacity and entropy of the system with different liquid 3 He, mixture, and solid 4 He contents, and use them to estimate the lowest temperatures achievable by the melting process, as well as compare our calculations to the experimental saturated 3 He− 4 He mixture crystallization pressure data. Realistic expectations in the execution of the actual experiment are considered. Further, we study the cooling power of the process, and find the coefficient connecting the melting rate of solid 4 He to the dilution rate of 3 He.

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“…where r and p have different values for the sinter and the plain cell wall. The acoustic mismatch model gives the exponent p = 3, but empirical values from various experiments are anything from below p = 2 to about 3 depending on the temperature range and the materials in question [16,17,18,19]. Attention has to be paid to the possibility that these parameters are in effect dependent on temperature as well.…”

mentioning

confidence: 99%

Thermal Conductivity of Superfluid $$^3$$He-B in a Tubular Channel Down to 0.1$$T_\mathrm{c}$$ at the $$^{4}$$He Crystallization Pressure

2019

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Our experimental assembly consists of a large main volume and a smaller sinter-filled heat-exchanger volume connected together by a narrow channel. Most of the main volume is filled with saturated 3 He-4 He mixture at its crystallization pressure together with solid pure 4 He, while the top of the main volume, the connecting channel, and the sinter volume are filled with liquid pure 3 He. The liquid phases in the main volume are monitored by two quartz tuning fork resonators. The system is cooled externally by a copper nuclear demagnetization stage, and, as an option, internally by the adiabatic melting of solid 4 He in the cell. Thermal behavior of this system gives rich information upon the thermal conductivity of 3 He in the connecting channel, as well as the Kapitza resistance between liquid helium and the plain cell wall in the main volume, and between liquid and the sinter in the heat-exchanger volume. None of those components are well-known apriori at 1 mK temperature range. In particular, the available thermal conductivity data of pure superfuid 3 He is very limited.

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Thermal boundary resistance between liquid helium and silver sinter at low temperatures

Cited by 8 publications

References 27 publications

Performance of Adiabatic Melting as a Method to Pursue the Lowest Possible Temperature in $$^{3}\hbox {He}$$ and $$^{3}\hbox {He}$$–$$^{4}\hbox {He}$$ Mixture at the $$^{4}\hbox {He}$$ Crystallization Pressure

Performance of Adiabatic Melting as a Method to Pursue the Lowest Possible Temperature in $$^{3}\hbox {He}$$ and $$^{3}\hbox {He}$$–$$^{4}\hbox {He}$$ Mixture at the $$^{4}\hbox {He}$$ Crystallization Pressure

Thermodynamics of adiabatic melting of solid He4 in liquid He3

Thermal Conductivity of Superfluid $$^3$$He-B in a Tubular Channel Down to 0.1$$T_\mathrm{c}$$ at the $$^{4}$$He Crystallization Pressure

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