WG8 Big Kelvinox Dilution Fridge Operation Instructions.

First cooldown.

Pre-cooldown

• System checks.
• Clean IVC indium seal with a paddle pop stick -- make sure you get the inside edge of the brass mating surface on the 4K plate.
• Check for touches between sample/cold finger and radiation can.
• Pump OVC (Pump out line, turn pump off and let turbo run down for 1 min, open valve until pump catches, restart pump).
• Attach floating box; check all pins are earthed.
• Mount device.
• Copper radiation can on. Remove end of can and visually check for touches to the cold finger; tap side of can and listen for any rattles that would indicate contact.
• Measure out indium wire, then clean the wire with alcohol and apply a very light coating of silicone vacuum grease. This makes it easier to clean after the run.
• Set the indium wire in the L-shaped lip on the IVC top, just inside the bolt circle. You'll have some excess material; cross one end of the wire over the other and trim.
• Attach IVC with indium seal. Be sure to tighten the bolts gradually so that the metal deforms evenly. Tighten in a star pattern first, then by sevens, fives and finally tighten all around. Check with an experienced fridge user if this isn't clear.
• Pump IVC and check bolts are tightened.
• Check for leaks with a leak detector (Optional)
• Fibreglass jacket on. (Be careful not to strip aluminium thread.)
• Pump out dilution unit on fridge (Connect condenser and return lines with T-piece. Pump out line. Stop pump, wait 1min, open gate valve, restart pump, then open condenser valve) This should pump for at least several hours to make sure there's no crud left behind from the previous run.
• Attach leak detector to dilution unit and monitor leak rate (Optional)
• Put exchange gas into IVC 1 neck-full of helium bladder.
• If you get an increased signal on the leak detector, you may have a leak from the dilution unit to the IVC. You must diagnose this before cooling the fridge, otherwise mixture can be lost.
• Load fridge into cryostat (Beware not to strip aluminium thread on fridge base.)
• Thermometers and heaters attached. (Can be done later)
• 3He condenser and return lines attached. (Can be done later)
• Main bath exhaust attached.
• Pump out cold traps (can use 1k pot via Vent1 or external pump via Vent2) These will be near 1 atm due to trapped gas during last run so pump out via 7, 11a, 11b while heating with the heat gun. (Can be done later)

Note

Leave main bath at 1 atm as much as possible. If main bath is at vacuum and OVC vacuum fails the cans will collapse (bad!). Do this also when changing pumps, etc on OVC.