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Venting, bake-out and degassing

Venting the analysis chamber

The analysis chamber can be open only during the shutdown period to insert evaporators needed for the following Run and/or to repair the equipment, as the total time of the whole operation including bake-out and degassing is at least 5 days.

For pumping and pressure reading in the analysis chamber we refer to this page. To vent the chamber:
  1. Switch off all devices in the analysis chamber - gauges (ionization and two cold-cathode), evaporators, sample annealing, X-ray source, electron analyzer, ion gun, LEED, titanium sublimation pump etc. Let the ionization gauge flange cool down.
  2. Check that the following gate valves are closed:
    • towards the refocussing mirror chamber of the beamline (electropneumatic valve 10),
    • towards the preparation chamber - bottom.
  3. Connect the nitrogen gas line to the venting valve of the big turbopump. Open partially the Swagelok valve to let nitrogen flow.
  4. Close the valve between the rotary vane pump and the sample manipulators. (For longer periods you can also switch the rotary pump off and immediately vent it by disconecting any KF flange.)
  5. Close the roughing valve between the big turbopump and the scroll pump. (For longer periods you can also switch the scroll pump off by disconnecting the plug.)
  6. Switch off the big turbopump and wait until it slows down below 100 Hz.
  7. Open the venting valve on the DCU controller (by enabling automatic venting by setting parameter 030 on the controller to 0) and check that the pressures in the neighbouring chambers do not increase.
  8. Wait until the chamber is fully vented (~30 min depending on how much you open the nitrogen valve). Bellows of the manipulator and the X-ray source retractor become soft when done.
  9. Close the nitrogen valve.
  10. Close the venting valve on the DCU controller (by disabling automatic venting by setting parameter 030 on the controller to 1).


After this you can open the selected ports, fix the necessary things, close properly all ports and start the pumps as following:
  1. Switch on the rotary vane pump of the manipulator (if off in step 4 above) and open the pumping valve of the manipulators.
  2. Switch on the scoll pump (if off in step 5 above) and slowly open the roughing valve below the big turbopump.
  3. Switch on the big turbopump and wait until it reaches 820 Hz (it can take up to 10-20 min).
  4. Switch on both cold-cathode gauges in the analysis chamber.
  5. When the displayed pressure is lower than 10-4 mbar switch on the ionization gauge.

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 can be as short as 12 hours so it can be performed overnight even during the experimental Run.

For pumping and pressure reading in the preparaion chamber - bottom we refer to this page and for the preparation chamber - top to this page. The venting sequence is:
  1. Switch off all the equipment in the preparation chamber(s) - cold-cathode gauge, evaporators, sample annealing, ion gun, titanium sublimation pump etc. Only the full-range gauge in the top part can stay on.
  2. Check that the following valves are closed:
    • gate valve towards the analysis chamber,
    • gate valve towards the load lock,
    • gate valve between the preparation chamber - bottom and the preparation chamber - top (if you do not vent the top part),
    • gate valve between the preparation chamber - top and the UHV part of the electrochemical cell (if you do vent the top part),
    • angle valve between the preparation chamber - top and the load lock (if you do vent the top part).
  3. Connect the nitrogen gas line to the venting valve of the turbopump of the preparation chamber - bottom. Open partially the Swagelok valve to let nitrogen flow.
  4. Switch off the turbopump of the preparation chamber - bottom. The venting valve will automatically open at 500 Hz.
  5. Wait until the chamber(s) is(are) fully vented (~15 min depending on how much you open the nitrogen valve). Bellows of the manipulator becomes soft when done.
  6. Close the nitrogen valve.


After this you can open the selected ports, fix the necessary things, close properly all ports and start the pumps as following:
  1. Switch on the turbopump of the preparation chamber - bottom.
  2. Wait until the turbopump reaches 1000 Hz (it can take up to 10-20 min).
  3. 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, 27 August 2020 09:36