Dilution Refrigerators

Dilution fridges (dil fridge for short) owe their cooling power to the incredible element helium and its two isotopes, helium-3 (³He) and helium-4 (⁴He). Though most people are familiar with it as the gas inside their party balloons (⁴He), helium can also condense into a liquid – but only at the very low temperature of 4.2 Kelvin (-269 degrees Celsius, or -452 degrees Fahrenheit). This property makes helium a very valuable cryogen in science. Using a condensation/evaporation cycle not unlike that of a kitchen refrigerator, a dil fridge takes 4.2 K liquid helium way down to 1.5 K.

The animation below illustrates how a dil fridge works. Use the play button to advance through the stages of operation.

Related Links

• Low Temperature Physics: The What, the How, the Why
  Why do physicists want to study things at temperatures so cold atomic motion almost comes to a halt? And how do they create such frigid environments, anyway? Read on for the what, how and why of low temperature physics.
• Cryogenics for English Majors
  Fear not, right-brained friends: Science and art intersect in plenty of places, and this is one of them. Samuel Taylor Coleridge lends a hand as we explore cryogenics – how to get things fantastically frigid – and the fascinating element that makes it all possible.
• What's Cryogenics?
  As defined by a Mag Lab expert.
• Millikelvin Facility: Frequently Asked Questions
  Questions and answers for scientists.

Thanks to the scientific adviser on this animation, Tim Murphy, director of the Mag Lab's Millikelvin Facility.