= Evaporative cooling
{disambiguate=atomic physics}
= Evaporative cooling
{synonym}
= Evaporative cooling of atoms
{synonym}
<Evaporative cooling of atoms> lowers the mean motional <energy> of a trapped gas by preferentially removing its more energetic atoms. Subsequent <elastic collisions> redistribute the remaining <energy>, producing a cooler approximately thermal sample.
In <forced evaporative cooling>, a decreasing trap-depth threshold or a <radiofrequency evaporation knife> continuously removes the high-energy tail. Losing atoms alone is insufficient: losses that sample all <energies> equally do not provide the same cooling mechanism. Useful evaporation increases <phase-space density of an atomic gas> while retaining enough collisions for rethermalization. An expansion measurement before and after evaporation tests the <velocity> distribution as well as the retained atom number.
Back to article page
