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 (the Vacuumbrand MV2 membrane pump labeled "AIRLOCK PRIMARY"); 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 12-13 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.

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Last Updated on Monday, 28 September 2020 12:06