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Clean LHe Cold Trap

  1. Pump mixture to the dump if it's not already there.
  2. When G1 < 1 mbar, you can close off V1.
  3. After an hour, close V6
  4. Once closed, close gate valve and condenser line speedivalve tightly to isolate the fridge if open. You do not want any contaminants to enter when cleaning the cold trap
  5. Close all valves on the IGH
  6. Ensure vent valve on back of IGH is closed tightly. We do not want to pump on the helium line or introduce any contamination
  7. Open valves 1, 2, 7, 2A and 5A on IGH to open up a route from the helium cold trap to He-4 pump
  8. Check that the routes between the cold trap and IGH are open. Also check that mixture is safe in dump (ie. there is no way you can pump on it by mistake). Additionally, check that the gate valve and condenser line speedivalve are closed, as are all valves on the IGH that you do not need. This step is very important! Put every ounce of effort into this step
  9. Turn on the He4 pump
  10. Extract the helium cold trap
  11. Wait for it to thaw. Once the cold trap has thawed, you can start heating it. If the cold trap is initially at room temperature, then leave the He4 pump working on it for about half an hour before you begin to heat it
    1. To heat a cold trap, use the heat gun (located in the bottom drawer of the black tool cabinet)
    2. You must heat all sides of the cold trap and all the way up and down its length
    3. To make sure you have heated each part sufficiently, drag a moist qtip across the surface of the cold trap. If it hisses, you have heated that surface well
    4. It's best to heat the cold trap in spatial increments to make it easier to test whether or not it's being heated well enough
    5. The cold trap needs to be heated completely 3 times
  12. Leave the trap pumping (via the He4 pump) for at least an hour after you're done heating it
  13. Once done, close all valves on the IGH and replace the cold trap back carefully in it's appropriate position. Make sure not to slam the cold trap down because it will probably hit the G10 plate and you want to avoid such a collision. You may have to maneuver the cold trap back and forth in order to the it to go through the hole in the G10 plate. Also, if the fridge is cold inside, lower the cold trap back into the MB slowly or it will boil off a lot of helium and increase the pressure inside the MB