Old Procedure

• IVC outside
• Mix loop
• 1K pot

• Put on the He recovery hose
• Open V4A, V1A to pump the Dewar until P2 reads 1mbar
• Close V1A, V4A
• Open V5A, V2A, and the rear speedivalve to evacuate the clear hose
• Close V2A, V5A; turn off the 4He pump
• Open He gas supply
• Open V2A, V5A, V4A and V1A
• When G3 starts to rise, close rear speedi valve, V2A, V5A, V4A, V1A
• Now the Dewar is filled over pressured He gas
• Leak check the system: leak<3×10^-8cc/s

• Turn on 4He pump
• Open V5A, V2A, V4A
• Close 1K pot needle valve
  • Don't over-tighten
• Open 1Kpot speedivalve
• When P2 ~0.01mBar, close speedivalve, V5A, V2A

• Isolate leak checker
• Close all valves on the pumping manifold
• Open the N2 gas supply
• Plug the hose to the exchange gas hose barb
• Open and close the exchange gas valve quickly
• Open the exchange bypass valve
• Check the pressure: 86mBar, if it’s too high, pump out some gas, otherwise
• Open the ebox valve
• Check pressure value: 4.6 mbar N2 gas

• Remove the middle plug
• Insert N2 transfer stick
• Put on the rubber hose
• Remove He recovery hose
• Open liquid N2 supply a little, let the hose cool
• Once the hose is cold, open the supply larger until the He resavar is full
• Close N2 supply
• Put on Ping pang ball

• Pump mixture into dump
• Close all valves on IGH
• Close Gate valve
• Close condenser line speedivalve
• Open V4, V12A(B), V13A(B)
• -12A can be fine-tuned, so we want to use that when we run the fridge. Thus, use 12B
• Wait for the gas to cool
• Turn on 3He pump (if not on)
• -do this by going to settings and check a box
• Open V14
• Open V6 to 13.2%. Keep G2-G1~10mbar
• -hard to achieve, so minimize difference as much as possible. Want G2>G1,. 13.2 is a reference number.
• Run at least for one hour

• Pump out exchange gas
• Prepare leak checker
• Cryoclean mixture
• Throughput test and leak check
• Pump out mixture
• Blow out liquid N2 using 200mBar He gas, when all the liquid is out, pressure of G3 will drop. Do a leak check while blowing out N2.
• Pumping and flushing the He reservoir: pump to 1mBar and fill He gas
• Evacuate 1K pot and isolate it
• Adding 4He exchange gas to IVC
• Start slow transfer of liquid He, hose should not freeze more than 2m.

• Pump Mixture into dump
• Close all valves
• Open Gate valve, condenser line speedivalve
• Open V3, V14, V9 and wait for G1 and G2 to stabilize
• Close V14, V3; Open V1
• Monitor pressure rise on G1

• Hookup rubber hose for blowing out
• Hookup recovery line
• Hookup He clear hose
• Open rear speedivalve
• Open V5A, V2A to evacuate He line
• Close V2A, V5A
• Turn off 4He pump
• Open He gas supply
• Open V2A, V5A, V4A wait G3>0
• Open V1A
• Adjust G3~200mBar (3psi)
• When G3 drops liquid is out

• [ organize screws ]
• Unscrew the fridge from the Dewar
• Unscrew the small bolts bolting the Dewar to the Al plate
• Unscrew the two big bolts slowly while keep the Dewar level
• Slowly lift the counterweights to lower the Dewar, make sure the Dewar won’t hit anything.
• Lower the Dewar all the way to the bottom
• Put a clean cardboard on top of the Dewar to keep dust out
• Cover the pit

• [ Clean the whole lab ]
• Wipe and vacuum the area around the fridge
• Put up the small clean room
• [ Clean the big clean room ]
• Dress up in clean room suits
• Wipe the smaller clean room with clean room wipe and methanol [ How ]

1. Stop circulation: close V6, then close V13A(B) and condenser line speedi-valve.
2. Pump mixture out of He cold trap: open V9, V5 (also V2 if there is mixture between V2 and V7), then wait until G1 can not go any lower, which is around 0.1mbar due to fluctuation, but it's likely higher.
3. Isolate He cold trap: close V5, V12A(B). If the steps below takes too long to complete, the reading of P1 may reach 1000 mar. In this case, close V9 and open V14 to let the mixture to expand into the dump.
4. Pull He cold trap out of bath: unscrew the quick coupling nut completely and pull the cold trap out of bath. Plug the He transfer port.
5. Warm up the cold trap and monitor pressure on G1 to see if there are any contaminant gas. Make sure G1 won't go above 1000 mbar. It's a good idea to have the He-4 pump ready right before pulling out the cold traps.
6. Pump contaminants out of the cold trap.
   1. Stop 1K pot: close 1K pot needle valve, then speedivalve, then V4A. Switch He-4 pump exhaust to exhaust port (yellow two way valve)
   2. Check to make sure the vent speedivalve behind IGH is closed. Open V5A, V2A and wait for P2 to drop to around 0.012mbar. Then open V7.
7. Take off the quick coupling o-ring and nut. Use a heat gun to heat the cold trap above 100 degree C. Then pump the trap for another half an hour or until G1 is low.
8. Isolate the cold trap: close V2, V7, V2A, V5A
9. Put the trap back into bath
   1. Put on quick coupling nut, retainer ring, and oring
   2. Insert the trap into the bath slowly.
   3. When hit the G10 plate, turn the trap back and forth to find the hole pass through it.
   4. Push it gently until it reaches the IVC flange and pull it back ~0.25“ then tighten the quick coupling nut.

Because V12A is leaky, N2 cold traps also need be cleaned when cleaning the He cold traps. In this case, V12A(B) need be open while pumping the mixture out the cold traps. And N2 cold traps need be pulled out of liquid N2 after He cold trap is out. Then heat up the traps and pump the contaminants out.