Practice question · Put in order
Arrange these cooling techniques in order of the lowest temperature they reach, warmest first.
- Pumped helium-3 at about 0.3 K
- Liquid helium-4 at 4.2 K
- Adiabatic demagnetisation below a millikelvin
- Liquid nitrogen at 77 K
- Dilution refrigeration at a few millikelvin
Hints
- Each stage is used to precool the next.
- Adiabatic demagnetisation is the last stage, reaching the lowest temperatures.
Show the answer
- Liquid nitrogen at 77 K
- Liquid helium-4 at 4.2 K
- Pumped helium-3 at about 0.3 K
- Dilution refrigeration at a few millikelvin
- Adiabatic demagnetisation below a millikelvin
Why
Each technique precools the next: nitrogen, then helium-4, then pumped helium-3, then a dilution refrigerator, and finally adiabatic demagnetisation. No single method spans the whole range.
Practise The Third Law and Low Temperatures
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