Re: Helium-3 vs. Helium-4
Helium-3, being a Fermion, should not exhibit superfluidity, a property of bosonic liquids. Helium-4 refrigeration below 2.17K is difficult because it goes superfluid and gushes through the tiniest of gaps, ask CERN....
<high voice> " we think the Helium is leaking"....
Of course, Fermions can pair-up, Cooper pairs, to make Bosons, and this is why electrons can become superconductors - and why, eventually, He-3 can become superfluid, but at a much lower temperature.