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Start 1 K Pot

In previous steps you've kept the 1 K pot evacuated so that no contamination would get inside and freeze. To cool the 1 K pot to ~ 1.8 K, you will pump on the 1.8 K pot with the He4 pump. By opening the speedivalve on the He recovery line and the gold needle valve, liquid helium will start to fill the 1 K pot, and the He4 pump will be pumping on the liquid. This will reduce the temperature of the 1 K pot appropriately. Before doing so, you need to close off the IVC. This is so that the turbo pump and the 1 K pot pump are not working against each other. The 1 K pot is a cryopump and if it is working against the turbo pump it may allow air to get into the IVC.

  1. At this point, the IVC should be thoroughly evacuated (pressure < 10E-6 mbar). Isolate the IVC now.
  2. Pump He3-He4 mixture into the dump (if not there already).
  3. Close all valves on the IGH.
  4. Turn on the He4 pump.
  5. Evacuate the line leading up to the 1 K pot - open V4A.
  6. You will now open the needle valve very minimally. Assuming you're on the ladder, positioned next to the IGH, and facing the needle valve, you will see a small hole in the needle valve. Use the 2 mm allen wrench to open the needle valve such that the hole is now facing the wall to your right (~ 1/4 turn). The purpose of this is to keep the needle valve from being overwhelmed by the He-4 pump when you open the speedivalve on the 1 K pot line in the next step, allowing the He-4 pump to pump on the 1 K pot.
  7. Open the large speedivalve on the 1 K pot line. The 1 K pot is now being pumped on.
  8. Keeping an eye on the 1 K pot temperature, which you can monitor on the IGH. Open the needle valve very slightly such that the temperature reduces to a range between 1.7 and 1.9 K
    • Note that opening and closing the needle valve increases/decreases the flow of liquid helium into the 1 K pot
    • The more liquid helium in the 1 K pot, the less ecient the pumping on the liquid (thus, evaporation of the liquid) is; therefore, the temperature will rise. Close the needle valve to reduce the flow liquid helium into the 1 K pot and decrease temperature, if needed
    • Switch the yellow valve from 'Exhaust' to 'Recovery'. Whenever pumping on the 1 K pot, this valve must be on 'Recovery' so that we may recover as much He-4 as possible.