Yeah, that is a challenge (the cryo part). I was, of course, a huge fan of the space program and in reading about things like liquid oxygen decided to try to make some. Lots of books about it talk about using compression and expansion of the gases to cool down atmosphere to the point where you can pull out the liquid oxygen. What I didn't appreciate at the time was CO2 freezes solid and nitrogen liquifies before oxygen does. So my setup of four air compressors, each being fed by the previous compressor and having their tanks cooled by an ice bucket failed in an interesting way. The third in the series seized up when the tank's CO2 froze into ice and blocked the output port, and then the tank "rapidly self disassembled" from the compressor as it warmed up and I was trying to debug the problem :-) The tank and compressor separated, the tank moved about 20 feet away while doing its impression of a balloon flying about the room as it deflated.

It killed me when the old Intel Santa Clara 4 facility was demolished to become data center space that they scrapped the Liquid N02 generator that was part of that building. I drove by one day and it was laying in the parking lot in pieces. I would have loved to figure out some way to save it, all that liquid nitrogen on tap for what ever evil mad science experiment I wanted. Sigh.