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Outgassing after bake-out

1. Before switching off the bake-out!

  1. Switch immediately on ion pumps in MCH and PCH; you might need to wait until they stop outgassing
  2. The out-gassing procedure is effective when pumping the MCH with the MCH turbo pump; therefore, please keep the gate valve to MCH turbo OPEN until the procedure is completed.
  3. Keep the Variac ON (180 V) during the entire outgassing procedure.
  4. You can also degas the ion gauges (press channel + right arrow)

2. Switch off the bake out

140°C: the MCH must quiclky reach the eights range with heaters off.

3. Gauges and TSP

  1. 140°C: Degas again the ion gauges.
  2. 130°C: Degas TSPs.
  • MCH (controller on the right hand side): use filament only; 2.7 A, 10 min.
  • PCH (only if installed). Filament and high voltage, so that emission reaches 50 mA.

4. 125˚C: let it cool!

open little gaps in the tent to speed up cooling.

5. 120˚C: start to degas

120°C: degas the Elmitec Au evaporator (if installed!): set the filament current to 2.0 A, high voltage 0 V and check that the temperature regulation is off. After some time T should reach 500˚C (do not worry, the TC is on the crucible and not well calibrated).

110°C: Start up the microscope HV rack and degas the sample manipulator, if this hosts a suitable sample such as a Mo dummy or W(110). Switch on the high voltage power supply (big green button). In order to degas sample and objective, set sample filament to 2.0 A (dia. is 0.125 mm), bombardment voltage to 10V (emission current should be negligible). After some time, the sample temperature will reach about 7 mV. Note that the rack cannot be switched on if the bake out controller is still on.

100°C: Degas TSPs:

  • MCH: use filament only; 2.7 A, 5 min.

  • PCH (if installed): HV on, with filament such that emission reaches 90mA emis (not more than 5 min).

6. 100˚C: remove the tent

Degas the Omicron evaporators. Try to degas all evaporators simultaneously. Connect the evaporators to the FOCUS controllers (in stand-by or off). Bring I fil to 2.0 A, HV = 0 and check that the maximum allowed shroud temperature is set to 300˚C (the controller has a protection). Once at 250˚C, set I filament to 0.5 A, so that the shroud temperature remains stable. Degas evaporators for about 2-3 hours.

Degas the other evaporators (if present). Notice that it may be better to retract the sample manipulator, in order to prevent the sample from being contaminated. Degas the SAES alkali dispencers installed (if any is present), taking care not to exceed the recommended activation current.

Keep on degassing the sample cartridge (and thusthe objective lens): filament to 2.2A, bombardment, bombardment voltage 200V . T sample should reach a temperature of about 10 mV.

Degas the sputter gun in PCH.  Connect the the cable to the ion gun feedthrough using extreme care, as the cable may exert a torque on the glass feedthrough, which is extremely delicate. When inserting the plug in the feedthrough, firmly hold the cable so that it does not rotate and release it only after the plus has been locked. Switch on the gun control unit (981-2046). In order to reset the DEGAS timer, always select the operate mode before switching to degas.

7. Before leaving...

  1. It is now time to switch everything off (Elmitec evaporators, Omicron, Sample heater). Fire the PCH TSPs once more (5 mins, 105 mA). Then go home and have some fun because this procedure is quite boring!
  2. start up the LEEM, that is switch on the lens supply and start LEEM 2000, so that all lenses are ramped up.

NOTE: Don't degas the QMS. NEVER EVER operate the multiplier if T > 50˚C and the total pressure is above the 10-7 torr range (2∙10-6 torr max)!!!! This may cause serious damage to the multiplier.

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Ultima modifica il Mercoledì, 28 Febbraio 2018 11:07