WG8 Big Kelvinox Dilution Fridge Operation Instructions.

Instructions copied from QED server by ARH from APM's file dated 4 March 2003.

1. First cooldown.

1.1 Pre-cooldown

1.2 Cool to 77K

1.3 Cool to 4K

1.4 Cool to Base

2. Operation at base

3. Remove the fridge

4. Put the fridge back in

5. Restart the fridge

6. Supplementary

6.1 Troubleshooting

  • K400FridgeSOPCrash - when in ciculation the fridge crashes (the mixture comes out of the fridge)
  • The mixture won't condense in the first place
    • It could be there is still exchange gas in the IVC thermalising the inner parts to the bath. Pump the IVC longer.
    • If the IVC was pumped for a long time, the inner parts may not have thermalised to the 4K bath, check the fridge resistors.

6.2 Temperature ranges

Base: Use fridge as usual. Base - 800mK: Use fridge with mixing chamber heater. 1.5K: Close 6, open 3, open 4, and close 12a. Use heater if higher temperature is needed. 4.2K: Need to remove mixture and let IVC up to He exchange gas. Emergency Shutdown • Don’t panic. Nothing happens very quickly, try to work out what has gone wrong. If magnet has quenched leave the room until the gas clears and it is safe to return. (Open bag ball valve to prevent it overfilling there is high boil-off.)

• Turn off the roots pump and then the 3He rotary. • Open valves 3,4 and 9 to let mixture back to the dumps (ensure dumps valves are open) and keep 1&6 open to allow mixture retreat from the fridge.

• Stop pumping pot by closing 4a then vent the pot to the bath by opening 1a and closing the needle valve.
Topic revision: r9 - 05 Dec 2021, MatthewRendell
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