Venting, bake-out and degassing

Venting the experimental chamber

The experimental chamber is usually being open during the shutdown period to insert evaporators needed in the following Run and/or to repair the equipment. The total time of the whole operation including bake-out and degassing is at least 5 days.

As the turpopump venting valve does not permit the connection of nitrogen gas we vent the experimental chamber is through the preparation chamber - bottom in the following order:
 
  1. Switch off all the equipment in both chambers - gauges (ionization and cold-cathode in the experimental chamber, cold-cathode in the preparation chamber - bottom), evaporators, sample annealing, X-ray source, electron analyzer, ion guns, LEED, titanium sublimation pump etc.
  2. Check that the following valves are closed:
  3. Open the gate valve between the experimental chamber and the preparation chamber - bottom.
  4. Connect the nitrogen gas line to the venting valve of the turbopump of the preparation chamber - bottom. Open the Swagelok valve to let nitrogen flow.
  5. Close the valve between the rotary vane pump and the line connected to the differentially pumped rotary feedthroughs of the sample manipulators.
  6. Close the valve between the turbopump and the membrane pump of the experimental chamber.
  7. Switch off the turbopump and the membrare pump of the experimental chamber and the turbopumping stage of the preparation chamber - bottom.
  8. Wait until both chambers are fully vented (~30 min depending on how much you open the Swagelok valve on the nitrogen line). It is done when the bellows on the sample manipulator becomes soft.
  9. Close the nitrogen gas inlet.

After that you can open the selected ports, fix the necessary things, close all ports and start the pumps as following:
  1. Switch on the turbopumping stage of the preparation chamber - bottom.
  2. Switch on the membrane pump of the experimental chamber and open the valve towards the corresponding turbopump.
  3. Switch on the turbopump of the experimental chamber.
  4. Open the valve between the rotary vane pump and the line connected to the differentially pumped rotary feedthroughs of the sample manipulators.
  5. Wait until both turbopumps reach full-speed operation (it can take up to 10-20 min).
  6. Switch on the cold-cathode gauge of the preparation chamber - bottom.
  7. Switch on the cold-cathode gauge of the experimental chamber.
  8. If the pressure is below 10-4 mbar switch on the ionization gauge of the experimental chamber.

Venting the preparation chamber

The preparation chamber (- bottom or both - bottom and - top) is vented if some custom equipment (usually evaporators) is to be installed there. The total time of the whole operation including bake-out and degassing is at least 12 hours so it can be performed overnight even during the experimental Run.

The venting using nitrogen gas is done in the following order:
 
  1. Switch off all the equipment in the preparation chamber(s) - cold-cathode gauge, evaporators, sample annealing, ion gun, titanium sublimation pump etc.
  2. Check that the following valves are closed:
  3. Connect the nitrogen gas line to the venting valve of the turbopump of the preparation chamber - bottom. Open the Swagelok valve to let nitrogen flow.
  4. Close the valve between the rotary vane pump and the line connected to the differentially pumped rotary feedthroughs of the sample manipulators (only if venting the preparation chamber - top where the manipulator is).
  5. Switch off the turbopumping stage of the preparation chamber - bottom.
  6. Wait until the chamber(s) is(are) fully vented (~15 min depending on how much you open the Swagelok valve on the nitrogen line). It is done when the bellows on the quartz crystal microbalance retractor or the sample manipulator become soft.
  7. Close the nitrogen gas inlet.

After that you can open the selected ports, fix the necessary things, close all ports and start the pumps as following:
  1. Switch on the turbopumping stage of the preparation chamber - bottom.
  2. Open the valve between the rotary vane pump and the line connected to the differentially pumped rotary feedthroughs of the sample manipulators (only if closed - step 4 above).
  3. Wait until the turbopump reaches full-speed operation (it can take up to 10-20 min).
  4. Switch on the cold-cathode gauge of the preparation chamber - bottom.


Now you can start preparing the bake-out, as described on the next page.

Last Updated on Thursday, 23 November 2017 10:01