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After using the dewar, you have to double-check that the output valve is closed See description below.
When you arrive at the system like this, you have to defrost the ice with a hair dryer. This is located in the cabinet in the entrance of the lab. You can start by chopping away frost and ice with some tool, but take care not to damage any valve or tubing on the dewar.Use the hair dryer to melt away the frost and ice combined with some careful chopping of the ice. the important area is just below the blue handle of the output valve. Here ice has formed that prevents the valve to be fully closed. There is a biuld-up of ice that makes the handle to stop before it is fully screwed in.
Use the hair dryer and gentle chopping to remove the ice at the top of the valve, under the blue handle, as indicated by the green arrow.
Then open the valve a bit and close it again, tightly. Use the big gloves for a better grip.
Continue to defrost the tube from the output valve until you clearly see the metal. Stop the hair dryer, and check for continued frosting. If this is still the case, the valve is not properly closed, and you have to remove more ice at the top of the valve, under the blue handle.
If the output pipe is not frosting the valve is really closed. See the last picture.
This check has to done after each use of the cooling in the CryoRIE!
So; if you open the valve to use LN2 for the cooling stage, you have to do this defrosting and check when you finish your session.
Ice must be removed between the top of the valve and the blue
handle.
Then the valve can be properly closed.
Here the valve has been fully closed.
The coupling to the output pipe
is fully defrosted, and is not frosting over again.