A miniature adiabatic demagnetization refrigerator with a magnetoresistive heat switch

Supanich, M.; Timbie, Peter

doi:10.1063/1.1457669

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…An alternative to these conventional heat switches are magnetoresistive (MR) heat switches which have been investigated for use in ADRs since 2002, although until now, no usable ADR using an MR heat switch has been successfully demonstrated [4][5][6]. At the Mullard Space Science Laboratory (MSSL), development of tungsten MR heat switches has been ongoing since 2005 [7].…”

Section: Magnetoresistive Heat Switchesmentioning

confidence: 98%

Performance of a fast response miniature Adiabatic Demagnetisation Refrigerator using a single crystal tungsten magnetoresistive heat switch

Bartlett¹,

Hardy²,

Hepburn³

2015

Cryogenics

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a b s t r a c tThe performance of a fast thermal response miniature Adiabatic Demagnetisation Refrigerator (ADR) is presented. The miniature ADR is comprised of a fast thermal response Chromium Potassium Alum (CPA) salt pill, two superconducting magnets and unconventionally, a single crystal tungsten magnetoresistive (MR) heat switch. The development of this ADR is a result of the ongoing development of a continuously operating millikelvin cryocooler (mKCC), which will use only magnetoresistive heat switches. The design and performance of the MR heat switch developed for the mKCC and used in the miniature ADR is presented in this paper; the heat switch has a measured Residual Resistivity Ratio of 32,000 ± 3000 and an estimated switching ratio (on thermal conductivity divided by the off thermal conductivity) of 15,200 at 3.6 K and 38,800 at 0.2 K when using a 3 T magnetic field. The performance of the miniature ADR operating from a 3.6 K bath is presented, demonstrating that a complete cycle (magnetisation, cooling to the bath and demagnetisation) can be accomplished in 82 s. A magnet current step test, conducted when the ADR is cold and fully demagnetised, has shown the thermal response of the ADR to be sub-second. The measured hold times of the ADR with just parasitic heat load are given, ranging from 3 min at 0.2 K with 13.14 lW of parasitics, to 924 min at 3 K with 4.55 lW of parasitics. The cooling power has been measured for operating temperatures in the range 0.25-3 K by applying an additional heat load to the ADR via a heater, in order to reduce the hold time to 3 min (i.e. approximately double the recycle time); the maximum cooling power of the miniature ADR (in addition to parasitic load) when operating at 250 mK is 20 lW, which increases to 45 lW at 300 mK and continues to increase linearly to nearly 1.1 mW at 3 K. To conclude, the predicted performance of a tandem continuous ADR utilising two of the miniature ADRs is presented.

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Section: Magnetoresistive Heat Switchesmentioning

confidence: 98%

Performance of a fast response miniature Adiabatic Demagnetisation Refrigerator using a single crystal tungsten magnetoresistive heat switch

Bartlett¹,

Hardy²,

Hepburn³

2015

Cryogenics

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“…We chose to use magnetoresistive heat switches because of their simplicity, reliability and short switching time [6]. These switches require superconducting magnets providing a field of several Teslas (see next section).…”

Section: Choice Of Heat Switchesmentioning

confidence: 99%

Design of a Miniature Adiabatic Demagnetization Refrigerator

Duval¹

2004

AIP Conference Proceedings

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In order to provide continuous cooling at 50 mK for space or laboratory applications, we are designing a miniature adiabatic demagnetization refrigerator (MADR) anchored at a reservoir at 5 K. Continuous cooling is obtained by the use of several paramagnetic pills placed in series with heat switches. We aim at a fast cycling process (≈ 500 s) in order to reduce the size of the pills. For that purpose, we developed and tested magnetoresistive heat switches based on single crystals of tungsten. They provide good thermal performance for a very short switching time, depending only on the ramping speed of the magnet used. Magnets for cycling the pills and the heat switches are made from high current density NbTi wires. High permeability materials are used to shield these magnets, which is crucial to minimize stray magnetic fields. The field in the heat switch magnets is maximized using a holmium core. The magnets have been modelled using a numerical simulation. Small magnets(≈ 100 cm 3 ) with an operating field of 3 T have been designed and tested with a ramping time of less than 30 s. We have tested a single-stage MADR with a small pill, magnetoresistive heat switch and fast cycling time. These tests confirmed the feasibility of our design.

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A miniature adiabatic demagnetization refrigerator with a magnetoresistive heat switch

Cited by 2 publications

References 5 publications

Performance of a fast response miniature Adiabatic Demagnetisation Refrigerator using a single crystal tungsten magnetoresistive heat switch

Performance of a fast response miniature Adiabatic Demagnetisation Refrigerator using a single crystal tungsten magnetoresistive heat switch

Design of a Miniature Adiabatic Demagnetization Refrigerator

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