Pumping down the SPELEEM

Pumping down

Pumpdown is made through the airlock chamber, using the airlock primary pump and the small Agilent turbo. Here's the procedre to follow:

1. Check that the airlock and MCH-PCH valves are open.
2. Check that the venting valve of the turbo pump is closed.
3. Then start the primary pump; when the pirani gauge indicates 10 mbar, start the Agilent turbo pump. When the turbo pump is in normal operation, the controller indicates 1350 Hz; power absorbed is 5-6 W.
4. Wait 15 minutes to give the turbo pump time to evacuate the MCH. Check that the airlock pirani shows "ur-4", which means the pressure is less than 5x10^-4 mbar.
5. Check the the Edward MCH turbo controller indicates full speed (100%). If not, abort this procedure. If yes, it means that you can open the turbo-to-MCH valve.
6. Wait 10-15 minutes to switch on the PCH and MCH ion gauges, starting with PCH and following with MCH.

Leak check

1. When the MCH pressure is in the 10^-7 range the QMS can be switched on and the leak-check performed. Type RGA3_0 in the Windows start up menu on the data acquisition PC making sure RS232 connection is configured on the right COM port. Then switch on filament and multiplier.
2. A ratio 18/32 lower that 50 indicates that there are no significant leaks.

REMEMBER: The multiplier can be switched on only if the total pressure is in the 10^-7 mbar range.