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Review of Adiabatic Demagnetization Refrigerators (ADRs)


First Spacecraft Use: the XRS ADR

The first ADR included in a spacecraft was the X-Ray Spectrometer (XRS), an x-ray astronomy instrument on the Japanese ASTRO-E satellite. Because the first satellite was lost when its launch vehicle failed in early 2000, the replacement ASTRO-E II is scheduled for launch in 2005. During testing, the XRS ADR showed that it could cool the x-ray astronomy sensors to temperatures as low as 60 milliKelvin and hold that temperature for over a day. The "warm" temperature heat sink for the XRS ADR was a bath of liquid helium at 1.3 Kelvin.

The Standard ADR: Operation

Our ADR Primer gives a description of the ADR and how it functions. For a less technical view, see theIntroduction to ADR's. Here is a brief description of the ADR:

The standard ADR consists of:

Salt Pill
A block of a paramagnetic substance, often a salt. (For example, the XRS ADR uses the salt ferric ammonium sulfate.) The temperature of the salt pill changes when the applied magnetic field is changed.
Magnet
The magnet is used to vary the magnetic field in the salt pill, causing the heating and cooling effect.
Heat Switch
The heat switch controls the flow of heat between the salt pill and the cooling bath or other thermal sink. Turned on, the switch allows heat to flow from the salt pill to the cooling bath (heat sink). Turned off, it blocks the heat from flowing back into the salt pill.

For the XRS ADR, the thermal sink is a bath of liquid helium at 1.3 Kelvin. For the advanced ADR, a mechanical cooler might substitute for the liquid helium.

The ADR operates in a cycle.

1. Warm up.
The magnetic field is turned on full. The salt pill temperature rises.
2. Dump heat to thermal sink.
The heat switch is turned on. Heat flows from the "hot" salt pill to the thermal sink.
3. Cool down.
The heat switch is turned off. The magnetic field is dropped rapidly. The salt pill temperature drops.
3. Cold part of cycle.
The cold salt pill cools whatever whatever it was designed to cool. (In the case of XRS, that would be X-ray sensors.)
4. Repeat
Return to step 1 and start over.
Return to Advanced ADR page.
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Curator: Brent Warner
NASA Official: Susan R. Breon
Last Updated: September 15, 2004