Exposing the sample with gases

Exposing the sample with gases

  1. Check that LEED, electron analyzer, X-ray source, evaporators, titanium sublimation pump etc. are off and that all gate valves to other chambers are properly closed.
  2. For the desired exposure in langmuirs (1 L = 10-6 torr×s) calculate the necessary pressure and time. Reasonable times are between 30 s and 30 min. The pressure must not exceed 1×10-6 mbar. This limit is dependent on the gas and exposure time, the rule is that the pressure after the exposure should go back down within reasonable time. Therefore be careful especially with water, methanol and similar liquids.
  3. Set the ionization gauge controller units to torrs using the UNITS button if needed:
  4. Start the Pressure Watcher software if needed. Bear in mind that the reading comes from the coarse cold-cathode and NOT the precise ionization gauge that we read in the end-station rack, so the reading might differ.

  5. Open slowly the corresponding leak valve. When you reach the desired pressure start the timer.
  6. Observe and adjust the leak valve if necessary.
  7. When finished close the leak valve. Do not use force.
  8. Wait for the pressure in the chamber to recover. The analyzer and the X-ray source cannot be operated before the cold-cathode pressure reading is below  5×10-8 mbar due to interlocks.
  9. Set the ionization gauge controller units back to mbars if needed.

Installing gas bottles (CO, O2, H2...)


  1. Close the valve on the bottle and disconnect the bottle.
  2. Connect the new bottle with the desired gas.
  3. Connect the small turbopumping stage to the Swagelok pumping valve.
  4. Close the manual venting valve on the turbopump.
  5. Start the turbopumping stage. The complete manual of the controller is here. Main parameters are:
    002 Standby slow speed operation in order to protect the turbopump from overload
    309 ActualSpd actual rotation frequency; it should be 1000 Hz
    340 Pressure pressure reading from the Pirani gauge on the pumped line
  6. Open the pumping valve and wait until the read pressure is low.
  7. Close the pumping valve.
  8. Open the valve on the bottle.
  9. Close the valve on the bottle.
  10. Repeat steps 6-9 at least three times. After the last step leave the valve on the bottle open.
  11. Switch the turbopumping stage off and wait until the turbopump slows down to half of the maximum frequency.
  12. Open slowly the manual venting valve on the turbopump until the rotation stops.

Installing liquids (H2O, CH3OH...)


  1. Disconnect the quartz glass flask, empty it and clean it.
  2. Fill it with about 1 cm level of the desired liquid and connect it back.
  3. Connect the small turbopumping stage to the Swagelok pumping valve.
  4. Close the manual venting valve on the turbopump.
  5. Start the turbopumping stage. The complete manual of the controller is here. Main parameters are:
    002 Standby slow speed operation in order to protect the turbopump from overload
    309 ActualSpd actual rotation frequency; it should be 1000 Hz
    340 Pressure pressure reading from the Pirani gauge on the pumped line
  6. Freeze the liquid with LN2.
  7. Open the pumping valve and wait until the read pressure is low or until the ice starts to thaw.
  8. Close the pumping valve.
  9. Leave the liquid thaw completely..
  10. Repeat steps 6-9 at least three times.
  11. Switch the turbopumping stage off and wait until the turbopump slows down to half of the maximum frequency.
  12. Open slowly the manual venting valve on the turbopump until the rotation stops.
Note: In order to avoid the cross-contamination of vapours it might be useful to bake-out the installed and pumped empty glass flask before installing the liquid.
Last Updated on Wednesday, 15 November 2017 09:15