Venting, bake-out and degassing

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Degassing

Some equipment must be properly degassed before use. It can be done at any time but it is convenient to do it until the chamber is still warm after the bake-out, so the degassed molecules adsorb less on other surfaces. Only the electron analyzer detector must be degassed after everything cools completely down!

The typical degas procedure consists of step-wise reaching the operating parameters while observing that the pressure does not rise much.

Titanium sublimation pump

The degas procedure is fully automated by the corresponding controller (degas knob) and consists of slow reaching 25 A filament current and keeping it for 15 min. It is enough to degas one filament. Nevertheless, the pressure significantly rises during every successive sublimation cycle (38.5 A, 1 min) up to 10-8-10-7 mbar. Observe the pressure during first several sublimation cycles after the bake-out and abort the sublimation if the pressure is too high..
Estimated time: 30 min.


Quadrupole mass spectrometer

No special degas procedure is required. Switch on the filament as described here and keep it on for about 30 min. You can also record the mass spectrum. If there is no leak in the chamber the intensity of mass 14 should be lower than that of mass 15.
Estimated time: 30 min


Sputter ion gun

The corresponding power supply provides an automated degas procedure activated by the DEGAS knob. It is enough to degas one filament.
For details see the corresponding manual.
Estimated time: 10 min.


LEED

The filament can be degassed either manually at ~2.50 A or using a built-in automatic procedure for few hours until the beam current is stable and in μA range.
For details see the corresponding manual.
Estimated time: 3 hours.


Knudsen-cell evaporators

The evaporators are degassed on first use by reaching the desired parameters.
Estimated time: 30 min.

X-ray source

The power supply provides semi-automated procedures for:
  1. conditioning of both filaments (by ramping the filament current; one at a time),
  2. high-voltage conditioning of both anodes (by ramping the high voltage; both at the same time), and
  3. power conditioning of both anodes (by ramping the emission current, one at a time). 
For details see the corresponding manual.
Estimated time: 15 hours.



Tectra e-beam evaporators

  1. If the filament is new it must be conditioned as described in the manual.
  2. Keep water cooling closed.
  3. With high voltage off slowly reach the filament current 6 A while observing the pressure.
  4. WIth high voltage on slowly reach the desired emission and wait until the temperature of the evaporator (read by an internal thermocouple) reaches 150-200 °C.
  5. Switch off the emission, filament limit and high voltage and wait until the temperature decreases below 100 °C.
  6. Open water cooling.
  7. With high voltage on slowly reach the desired emission and keep it on for several minutes.
  8. Switch off the emission, filament limit and high voltage.
  9. After several minutes close water cooling.
Estimated time: 2 hours.

Oxford e-beam evaporator

  1. Connect the desired pocket as described here.
  2. If the filament is new it must be conditioned as described in the manual.
  3. Open water cooling.
  4. With high voltage off slowly reach the filament current 6 A while observing the pressure.
  5. WIth high voltage on slowly reach the desired emission and keep it on for several minutes.
  6. Switch off the emission, filament limit and high voltage.
  7. Repeat for other pockets if needed.
  8. After several minutes close water cooling.
Estimated time: 2 hours.



Sample manipulator and sample

The degas happens at first several cycles of sample annealing.
Estimated time: 30 min.




Electron analyzer detector

Warning: this is the only degas procedure that must be done after complete cooling down. Wait at least 72 hours after the end of the bake-out!

The detector is degassed by slowly increasing the voltage from 0 up to ~2000 V with all excitation sources off. It is done by using the detector voltage scan saved in the yymmdd_start-up.xml file in the current dara folder (D:\Data\20**\inhouse\). For parameters you can use any recent file.
For details see the corresponding manual.
Estimated time: 30 min.

Last Updated on Tuesday, 09 April 2024 11:48