He Leak Check Tips
1.
Establish background intensity reading first.
2.
Once you find a significant signal, test the time delay constant.
3.
Do not take apart the first place where you see a significant signal. It may be just caused by the real leak in a region close by, that has a much higher signal.
4.
How close is “close-by”? Depending on internal air flow in your equipment in the area you are doing leak check, He can be detected pretty far away.
5.
Don’t be blinded by your own hypothesis. Instead, draw a map and write down spectrometer intensity reading on various locations on the map. Try to locate the place with global maximum intensity reading.
6.
Once you are on the exactly location, the signal is typically orders of magnitude higher than the region surrounding it.
7.
Once you locate the area that has the global maximum, identify the fittings around it.
Spray directly to them one at a time. The real leak should have a signal orders-ofmagnitude higher than the region surrounding it.
8.
A 10
-4
~10
-3
SCCS leak is a medium sized one. > 10
-2
SCCS is a large one, <10
-4
is a small one. These sizes are actual sizes of total Qload generated by the leak. The size detected by the He leak checker is typically an least one order of magnitude smaller than the actual size of the leak because <10% of the gas sucked into the leak is actual He, most of it is just air, no matter how well you spray into the leaking orifice.
Varian 979 He leak Detector Operation Procedure
To turn on:
1.
Have inlet flex hose connected to the test port of your vacuum system. Make sure you already pump down your vacuum system as low as you can. Keep the isolation valve or your test port shut at this moment so that your vacuum system and the leak checker are still isolated from each other.
2.
Power on the leak checker.
3.
At the point, the leak checker is not ready yet. Your blue screen menu display will say that the system is waiting and the LED under the Hold button should be lit. It will also say test port pressure is at 760Torr.

4.
When the leak checker is ready, it will say system ready on the blue screen. Also it will say test port pressure is at 1mTorr. Your detector reading will also go down at the same time all the way to the lower limit of 1X10
-9
SCCS. At this point, you can press the test button. The LED above the Test button will light up. The system is ready for use now.
5.
Now you can gradually open up your system’s test port isolation valve to connect your system to the leak detector. Take care you never allow the leak detector test port pressure to rise above 1Torr.
Shut down procedure:
1.
Close the isolation valve of the test port of your vacuum system. Your detector reading will go down all the way to the lower limit of 1X10
-9
SCCS, test port pressure will do down to 1mTorr.
2.
At this point, you can press the Hold button. The LED below it should light up.
3.
Then press the vent button. The test point pressure will go up to 760Torr. The inlet flex tube will be vented.
4.
Now you can turn off the power.