Advertisement
saturation limit of the filament. With the limit set (highlighted), the operator can turn
the Filament knob clockwise indefinitely without fear of oversaturating the filament.
Turn the filament up to a number that is 4 or 5 less than the indicated filament limit.
c. DEFOCUS the electron beam by TURNING the Intensity knob clockwise to strongly
OVERFOCUS the C2 lens. BRING the beam back to crossover (the smallest image of
the beam) and CENTRE it with the Shift X/Y knobs.
d. CHOOSE a C2 aperture (Position 3 which is a 100-µm aperture) by ROTATING the
largest knurled knob on the topmost aperture control on the column to the desired
position.
e. USING the Intensity knob, slowly OVERFOCUS (TURN clockwise from crossover) the
beam to coincide with the diameter of the intermediate-sized black circle on the
phosphorescent viewing screen. If the defocused beam is not coincident with the
circle, adjust it using the C2 aperture centering controls. These are both the
intermediate-sized knurled knob on the aperture rod and the knurled knob on the
side of the assembly (to the right). DO NOT TWIST THE SMALLEST, INNERMOST KNOB
(WHICH IS NOT KNURLED) BECAUSE IT UNSCREWS THE APERTURE ROD. Repeat these
steps (c and e) until the beam spreads uniformly around the reference circle while
being overfocused (Intensity knob).
f. USING the Intensity knob, adjust the beam to crossover. PRESS the Fine button (to the
left of the Intensity knob; the indicator light turns green when it is on) and use the
Intensity knob to sharpen the desaturated filament image. CENTRE the image using
the Shift X/Y knobs.
g. PRESS the Stig button on the right-hand instrument panel to open the Stigmator
Control page.
h. PRESS the Cond key on the data monitor screen to SELECT the C2 lens for astigmatism
correction. USE the Multifunction X/Y knobs, while rotating the beam through
crossover using the Intensity knob, to obtain the cleanest, roundest desaturated
filament image possible.
i. PRESS the Stig button to return to the Configuration page.
j. TURN the Filament knob clockwise to fully saturate the filament. When the saturation
point (as defined by the FIL LIMIT) has been reached, the microscope will emit a
'beep.'
k. PRESS the Ready button and then the TEM key to return to the TEM
page.
l. USING the lever to the left of the viewing chamber, lower the small phosphorescent
screen into place. Insert the beam stop (at the right-hand side top of the viewing
chamber) so that it will be visible across the small screen. Use the binoculars to
observe the beam stop. To adjust the binoculars for your eyes, first adjust the
2017.07.07
BRIGHTFIELD
12
Advertisement
