Construction of Continuous Magnetic Cooling Apparatus with Zinc-Soldered PrNi$$_5$$ Nuclear Stages

Takimoto, Shohei; Toda, Ryo; Murakawa, Satoshi; Fukuyama, Hiroshi

doi:10.1007/s10909-022-02801-0

Cited by 4 publications

(4 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The measured R HSW was 114 nΩ, meeting our requirement. It agrees reasonably well with the expected value (= 107 nΩ) estimated from the test measurements for individual parts including the known residual resistance of an electron-beam welded Ag piece similar to the present case in size (= 13.5 nΩ [9]).…”

Section: Assemblingsupporting

confidence: 90%

“…Here, R NS1 , R NS2 and R HSW2 are the residual electrical resistances of NS1, NS2 and HSW2 in the closed mode, respectively. Since a realistic evaluation for R NS2 or R NS1 is quite low (≈ 140 nΩ) [9], R HSW2 should also be of the order of 140 nΩ or less not to spoil the cooling power of the CNDR. This means α min = 0.21 mm if the main resistance of HSW2 is in the Zn region.…”

Section: Constraint For Aspect Ratio Of Superconducting Elementmentioning

confidence: 99%

“…After the proposal of Ref. [5], the development of CNDR is now being extensively conducted [6,7,8,9].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Superconducting zinc heat switch for continuous nuclear demagnetization refrigerator and sub-mK experiments

Toda¹,

Takimoto²,

Uematsu³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

We have developed and tested a zinc superconducting heat switch suitable for magnetic refrigeration and calorimetric experiments at sub-millikevin (sub-mK) temperatures. The specific application here is an adiabatic demagnetization refrigerator with two PrNi 5 nuclear stages, which can keep a temperature of 0.8 mK continuously, (CNDR) proposed by Toda et al. (J. Phys.: Conf. Ser. 969, 012093 (2018). The switch consists of six high-purity zinc foils of 0.25 mm thick which contact seven silver foils by diffusive bonding. The silver foils are electron beam welded to silver rods that are thermal links to other components. The choice of the thin zinc foils is due to reduce the magnetic latent heat on switching and the contact thermal resistance under a constraint on the aspect ratio of the switch element. The measured thermal conductance of the whole switch assembly in the normal (closed) state, K closed , agrees very well down to 70 mK with the value estimated from the residual electrical resistance 114 nΩ at 4.2 K, indicating the validity of the Wiedemann-Franz law for zinc. The measured thermal conductance in the superconducting (open) state, K open , follows nicely the prediction from the BCS theory and approaches the value expected from the Debye model for thermal phonons near 70 mK. The heat leak through the HSW from the higher temperature side of 30 mK at most is estimated to be less than 0.5 nW, which is much lower than the expected cooling power (= 10 nW) of the CNDR at 0.8 mK . The switching ratio K closed /K open extrapolated to 30 mK, is as high as 5×10 4 . All the test results meet the requirements for the CNDR and, for example, heat capacity measurements at sub-mK.

show abstract

Section: Assemblingsupporting

confidence: 90%

Section: Constraint For Aspect Ratio Of Superconducting Elementmentioning

confidence: 99%

See 1 more Smart Citation

Superconducting zinc heat switch for continuous nuclear demagnetization refrigerator and sub-mK experiments

Toda¹,

Takimoto²,

Uematsu³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…This was achieved using indium as a solder [51]. Cadmium has traditionally been used for this purpose [48] but has higher toxicity, zinc has recently been proposed [62] as an alternative material. Although indium limits the final field to be in excess of 28 mT, the superconducting critical field of indium, it did not compromise the achievement of the performance objectives.…”

Section: Design Detailsmentioning

confidence: 99%