Leak Checker

Main Contact: U Nasti

The Adixen vacuum pump has a Leak Checker attached to it. It is the long grey retangular unit (RGA100l) and is kept at low pressure by keeping the valve (Red) closed. The small 9L He bottle is in the main lab 222b clamped beside the Tc test setup.

SRS RGA 100 online manual - link broken!

http://www.nanophys.kth.se/nanophys/facilities/nfl/aja/manuals-pdf/RGAm.pdf

To use the leak checker, first pump the system down to a pressure lower than 2*10^-2 mBar (The leak checker won't turn on above this pressure). Then you can flick the switch on the back of the leak checker on. If their are any red lights on the back of the leak checker, it's likely a connection is faulty, or the pressure is too low. Connect the leak checker to the laptop (R323/USB). On the laptop, open the program (RGA). Go to the Head menu, select Connector List Setup. Double click the RGA icon, it should turn green, click ok. The corresponding green light should appear on the leak checker. On the main screen there is a selection of graphs, choose the 'Leak Test' option. Now, turn on the filament (Toggle on/off filament) by clicking the squiggly wire button. The corresponding green light should appear on the leak checker. On the main screen, click GO and leak checking should start. You can turn on the audio aswell as looking at the trace.

The 9L He bottle with hose is for leak testing. The flexible hose is very leaky. You MUST close the main valve on top of the bottle after you have charged the hose.

Helium 900 Bar CP Grade L Cylinder 9.05 m^3

Telltale signs of a cryostat leak are: inability to pump down to a low pressure (5 x10-5 mbar in the GM cooler type after 1 hour with the turbo station), condensation or frost outside the cryostat when cold or warming up.

If the cryostat is cold and you suspect a leak, connect it to a pump and warm up. Make sure the main clamp is loosened to avoid any overpressure during warmup.

For leak testing best practice is to squirt a brief burst of He at each location then wait for a response from the RGA. He gas rises, so start from the top and work down the body of the cryostat. Monitor the pressure as the system pumps out and log in the cryostat log book.

Replacing the gas bottle. The bottle is rented from BOC, who pick up the empty one from the cage outside the level 2 workshop and drop off a refill. Place an order for a refilled bottle. Move the bottle to the cage using a gas bottle cart (Denis Kearns x4306 can assist - the gas bottle cart is stored beside the janitor's office on level 2). The combination lock for the cage is 5246 and you need to press the button on the underside to open the lock.

JWNC Leak Checker

We have the option to borrow the leak checker from the dry etch lab in the JWNC. The also have a He-bottle in the same lab. Contact Mark Dragsnes, Dougie Lang.

For general gas/vacuum assistance Colin Roberts still works 2 days a week in the Rankine Building (based in Richard Hogg's lab on level 2)

Please take good care of these items and return quickly once testing is complete.