So from what i understand the dilution unit holds the mixture of 3He and 4He (with 3He floating at the top, 3He gas under that and 4He at the bottom)
So the still line sucks up 3He gas (and some 4He liquid?) then runs that mixture past the 1k Pot where it condenses the 3He gas back to a liquid and repeats
So i guess my question is if it whats going on with the 4He is it being sucked up in the still line? and is the 1K pot there just to condense the 3He?
Very little He4 is circulated, which is possible because the vapor presssure of He4 is much lower than He3. The He3 is effectively "distilled" from the mixture (hence the name "still"). Yes, the main reason for having a 1K pot is to condense the returning He3 gas.