Magnetic Cooling

Ambler, E.; Hudson, R. P.

doi:10.1088/0034-4885/18/1/307

Cited by 59 publications

(19 citation statements)

References 209 publications

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“…The transfer of thermal energy by phonons across a boundary is given by Eq. (1) [6], where dQ/dt is the heat flow across the boundary, A is the contact area, T 1 -T 2 the temperature difference across the boundary and b the thermal transport parameter. The value of dQ/dt is strongly dependent on temperature, therefore at low temperatures, a large temperature gradient can exist across a boundary; this is a severe problem at temperatures in the 100 mK region thereby necessitating either very low energy exchange across the boundary or large contact surface areas.…”

Section: Thermal Boundary Resistancementioning

confidence: 99%

Design and performance of a fast thermal response miniature Chromium Potassium Alum (CPA) salt pill for use in a millikelvin cryocooler

Bartlett¹,

Hardy²,

Hepburn³

2015

Cryogenics

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a b s t r a c tThe design and performance of a fast thermal response miniature (24 mm outer diameter by 30 mm long) Chromium Potassium Alum (CPA) salt pill is described. The need for a fast thermal response has been driven by the development of a continuously operating millikelvin cryocooler (mKCC) which uses 2 T superconducting magnets that can be ramped to full field in 30 s. The consequence of magnetising and demagnetising the CPA pill in such a short time is that thermal boundary resistance and eddy current heating have a significant impact on the performance of the pill, which was investigated in detail using modelling. The complete design of a prototype CPA pill is described in this paper, including the methods used to minimise thermal boundary resistance and eddy current heating as well as the manufacturing and assembly processes. The performance of the prototype CPA pill operated from a 3.6 K bath is presented, demonstrating that a complete CPA cycle (magnetising, cooling to bath and demagnetising) can be accomplished in under 2.5 min, with magnetisation and demagnetisation taking just 30 s each. The cold finger base temperature of the prototype varies with demagnetisation speed as a consequence of eddy current heating; for a 30 s demagnetisation, a base temperature of 161 mK is obtained, whilst for a 5 min demagnetisation, a base temperature of 149 mK was measured (both from a 3.6 K and 2 T starting position). The measured hold times of the CPA pill at 200 mK, 300 mK, and 1 K are given, proving that the hold time far exceeds the recycle time and demonstrating the potential for continuous operation when two ADRs are used in a tandem configuration. The ease and speed at which the CPA pill temperature can be changed and controlled when stepping between operating temperatures in the range of 200 mK to 4 K using a servo control program is also shown, once again highlighting the excellent thermal response of the pill. All of the test results are in good agreement with the modelling used to design the CPA pill, giving good confidence in our ability to understand and estimate the effects of eddy current heating and thermal boundary resistance. To conclude, the design for the CPA pill to be used in the mKCC (which is heavily based on the design of the prototype) is presented.

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Section: Thermal Boundary Resistancementioning

confidence: 99%

Design and performance of a fast thermal response miniature Chromium Potassium Alum (CPA) salt pill for use in a millikelvin cryocooler

Bartlett¹,

Hardy²,

Hepburn³

2015

Cryogenics

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“…To satisfy this cooling requirement, 3 He was chosen as the working gas in the 1.7 K Joule-Thomson ( J-T) circuit because of its higher vapour pressure compared with 4 He. The J-T circuit for 3 He is thermally connected with the two-stage Stirling cryocooler (2ST) at the 20K stage and the 100K stage. Figure 2 illustrates the cold stages of the three heat exchangers of coaxial double tubes assembled in the vacuum chamber for experiments.…”

Section: Spacecraft Cryocoolersmentioning

confidence: 99%

Thermal design of the SPICA/ESI instrument

et al. 2006

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The ESI instrument (European SPICA Instrument) is a proposed imaging spectrometer for the 30-210µm band for the JAXA SPICA mission. The instrument will have unprecedented spatial resolution and sensitivity due to the large Ø3.5m telescope aperture, cold fore-optics (~5K) and high sensitivity detectors (NEP~10 -19 W/√Hz). One of the key technical challenges of the design of the instrument is the thermal architecture due to the mass and cryogenic heat load constraints and the need for very low temperatures. Two candidate detector technologies have been pre-selected for inclusion in the instrument Phase-A study; Photoconductors and TES Bolometers.An overview of thermal architecture of the SPICA spacecraft is presented in order to explain the thermal interface constraints imposed on the instrument. Proposed thermal architectures for the instrument for both the TES and the Photoconductor options will be outlined including a novel design for a lightweight hybrid cooler for achieving sub 100-mK detector temperatures. This novel cooler architecture utilizes a combination of ADR and sorption coolers. Several design solutions for achieving high thermal isolation generic to both detector options are presented.

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“…The maximum magnetic entropy per mole expected for one isolated Gd III ion is 2.08R = 49.2 J kg 4 . 36 The values indicated in the table correspond to the maximum mass and volumetric magnetic entropy variations at the temperature T m for magnetic field variations of 2 T and 7 T. The choice of a field change µ 0 ∆H = 2 T is dictated by the fact that, for widespread applications, the interest is chiefly restricted to applied fields which can be produced by permanent magnets.…”

mentioning

confidence: 95%

“…1 Its use through the adiabatic demagnetization process has first focused on low temperatures. [2][3][4] Different kinds of materials have attracted interest for their MCE in low temperature region (2-4 K), including simple paramagnetic salts, 4,5 molecular nanomagnets, [6][7][8][9][10][11][12] extended porous networks, 13 garnets, 14 or intermetallic alloys. 15 For a more exhaustive insight, two recent review articles dealing with coordination compounds 16 or molecule-based 17 magnetic coolers can be consulted.…”

mentioning

confidence: 99%

Magnetocaloric effect in gadolinium-oxalate framework Gd2(C2O4)3(H2O)6⋅(0⋅6H2O)

et al. 2014

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Magnetic refrigerants incorporating Gd3+ ions and light organic ligands offer a good balance between isolation of the magnetic centers and their density. We synthesized the framework material Gd2(C2O4)3(H2O)6⋅0.6H2O by a hydrothermal route and characterized its structure. The honeycomb lattice of Gd3+ ions interlinked by oxalate ligands in the (a,c) plane ensures their decoupling in terms of magnetic exchange interactions. This is corroborated by magnetic measurements indicating negligible interactions between the Gd3+ ions in this material. The magnetocaloric effect was evaluated from isothermal magnetization measurements. The maximum entropy change −ΔSMmax reaches 75.9 mJ cm−3 K−1 (around 2 K) for a moderate field change (2 T).

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Magnetic Cooling

Cited by 59 publications

References 209 publications

Design and performance of a fast thermal response miniature Chromium Potassium Alum (CPA) salt pill for use in a millikelvin cryocooler

Design and performance of a fast thermal response miniature Chromium Potassium Alum (CPA) salt pill for use in a millikelvin cryocooler

Thermal design of the SPICA/ESI instrument

Magnetocaloric effect in gadolinium-oxalate framework Gd2(C2O4)3(H2O)6⋅(0⋅6H2O)

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