Using what Liquid gas to cool TYPE I Superconductors?

[Wiz700]

So,

Liquid Nitrogen or Liquid Helium to cool Type I(Lead/Aluminum) superconductor?
I know its best to use Liquid Helium, but can I use Liquid Nitrogen and go below the BC of those materials?

 

[f95toli]

No, because liquid nitrogen boils at 77K, and even if you pump on it the temperature will only go down a few K before it goes solid (I can't remember the exact temperature, 68K or so at 1 Bar?)

Hence, liquid nitrogen only works for high-Tc superconductors, and they are all type II.

Also, for aluminium you can't even use liquid helium (bulk Tc=1.2K), you need something more elaborate; you need to e.g. pump on He-3 (or He-3/He-4 mixtures) or use adibatic demagnetization cooling.

 

[Wiz700]

No, because liquid nitrogen boils at 77K, and even if you pump on it the temperature will only go down a few K before it goes solid (I can't remember the exact temperature, 68K or so at 1 Bar?)

Hence, liquid nitrogen only works for high-Tc superconductors, and they are all type II.

Also, for aluminium you can't even use liquid helium (bulk Tc=1.2K), you need something more elaborate; you need to e.g. pump on He-3 (or He-3/He-4 mixtures) or use adibatic demagnetization cooling.

Hence, another reason why people prefer Type II superconductors.