|Phase cooling would be more effeicent. NoL can build u a 3/4 stage that can give you -200 degrees 24/7( about 5000 dollars tho)|
|Pics or it didn't happen|
Also we put together cascades with autocascading J-T stages that can see -140C all day at rather high loads. I'm designing a -70C or so high load machine around your single stage sized cases, and then maybe something a bit bigger like those rotary cases Little Devil has, that can do -100C or colder. Single compressor autocascade.
Probably will end up selling it, but we will see what the market value around here dictates.