JEOL JSM-6390 LA, Руководство пользователя

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52
J. M. Allaz © March 14, 2021
A2) Activating the SEM in W-mode
In a normal situation, the SEM is working under ultra-high vacuum (UHV) using an ion pump
in the gun. However, some situation might force us to shut down the ion pump and to work
only under “high vacuum” condition using only the rotary and the turbo pumps. Such an
exceptional condition is commonly related to a vacuum leak in the gun or a problem with
valve VT-1 or VT-3 and is only temporary. In this situation, only a W-filament can be used.
WARNING: Follow these instructions ONLY when…
(1) the SEM is loaded with a W-filament ( green sign )
AND (2) when the SEM is in “W-mode” ( blue sign ).
The vacuum reading on the box on the left side of the SEM will be OFF. The light “UHV” will
always remain orange, and both lights “Column” and “HV” will be either green when a
sample is loaded (SEM under high vacuum) or orange when you open the sample chamber.
When the W-mode is in use, both valves VT-1 and VT-3 are OPEN. This implies that each
time you vent the instrument, the vacuum is lost in the chamber and in the gun. You must
therefore TURN OFF the filament heat each time you perform a sample change or at the
end of your session. Follow these instructions to LOAD your sample:
•
Lower the filament saturation to zero and turn OFF the electron gun (button HT OFF).
•
Click on “Sample” and press “Vent”. The HT button will turn grey and state “Wait…”.
•
Open the chamber and load your sample.
•
Take a photo with “SNS” as usual. Then, lower the stage to 30 mm.
•
Close the sample chamber (keep an eye on the IR camera!).
•
Press the button “EVAC” to pump.
•
Wait for the signal “READY”.
•
The HT button should now be blue. Press on it to turn HT button ON (green).
Perform then a
filament saturation by setting the filament heat to its optimum ( Fig. A5 ):
•
Remove the “Beam blank”.
•
Insert the Faraday cup by pressing the button “PCD”.
•
Press the top-left button “CONFIG / LOCAL” on the ammeter. This will activate the
live beam current reading. If the ammeter displays “CONFIGURATION”, press
another time on the “CONFIG / LOCAL” button. If you still don’t see a live reading of
the beam current, press the button “TRIG”.
•
At first, the ammeter should indicate a value around zero.
•
Set the “Spotsize” to around 74-78 (= medium to high beam current).
•
Open the window “Gun” and increase the filament heat until the emission current and
the beam current increase. Continue increasing the heat, until the beam current start
decreasing again as you are passing the “false peak”. Continue increasing the heat
until the beam current increases again. You will reach the saturation point when the
increase in beam current slows down significantly or plateaued or drops down slightly
(= saturation point). When you are at saturation
lower by one or two clicks the heat.
•
The emission current should read at least ~30 to 50 µA or more.
•
The ammeter should read ~2 to 3 nA when the beam aperture #2 is in use.
•
When done, click on “PCD” to remove the Faraday cup.
•
You should now see an electron image on the screen.
Perform then a beam alignment following the instructions in
Section F .
W-
mode
Ion pump is NOT
working, no UHV...
W