the copper piece on Sample diphon was leaking helium gas to IVC during sample change process. This iece was replaced with a new piece.
Few tips :
-use Certanium 34C solder with its flux
-clean the inside of the SS tube relly good
-hold the tube as normal vertical operating position for soldering
-don't put too much solder!
-check the flow of helium liquid in and gas out before soldering and after
-mazimize the number of threads that are sticking out of the copper torque piece