By Kristen Coyne
WANT TO KNOW MORE?
Read Cryogenics for English Majors, a primer on the topic.
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.