Philips SEM 525 User manual

PHILIPS SEM 525 INSTRUCTIONS
Start-up:
Turn master mains switch on (if not already on)
Turn the water cooler/circulator timer on to HOLD (counter clockwise)
Press the SEM mains utton ON (lower left panel, listen for the mechanical
vacuum pump to come on)
Press the vacuum ON utton
The red high vacuum light (left most panel) will e lit. After a out 30
minutes, this light indicator will turn off indicating a sufficient vacuum to
operate the microscope. However, to ensure maximum filament life, do not
turn the eam on until the vacuum gauge reads well elow “10”.
Turn o n the exposure light column switch.
Turn o n the “marker” switch.
Turn ON the detector and adjust the “Black Level”.
Set the detector to GREY SCALE and adjust rightness and contrast for the
display screens (once set, this does not change apprecia ly over time).
If using the Polaroid camera, press and hold the photo start utton and
press the scan rate 2000 and 32 uttons. This sets the scan rate for the
camera screen. The photo scan can e stopped y pressing the interrupt
utton.
Adjust operating parameters appropriate to the specimen characteristics.
Select accelerating voltage:
For maximum resolution and high magnification work, use 25 kV or a ove
with gun ias setting of “1” and a spot size of 20 or 10. This electron eam
will penetrate well into most samples and require a lower secondary
electron detector gain setting. The detector ias may e turned to negative
to detect ackscattered (BS) electrons if desired, ut there will e a lot of BS
electrons with this kV setting. A etter BS image will e o tained using a
lower accelerating voltage.

Use gun ias 1 for
20 and greater kv
and ias 2 for 10 –
20 kv.
Use a spot size of 500
and the lowest
magnification to align
the electron gun.
Non-conductive samples may charge with these settings. Biological
specimens that have een coated usually can e viewed with a lower
accelerating voltage, usually 10 – 15 kV. With this setting, set the gun ias
to “2” so as to keep the emissions current in a safe range of 30 – 40 µA. A
lower kV setting usually improves the surface image ut also adds “noise” to
the detector signal.
With the Wehnelt gun cap fitted with a 200 µ aperture, and the filament to
Wehnelt distance adjusted 6 small divisions, the following should e
expected at filament saturation:
Bias 1, 25 kv, saturated filament current = 40 µA.
Bias 2, 10 kv, saturated filament current = 35 µA.
To lower the saturated filament current, increase
the filament to Wehnelt distance.
Select pot ize:
Generally speaking, use a large spot size (200 or
500) for low magnification work under 1000 x
magnification. Smaller spot size is used for higher
magnifications. As spot size is reduced, the
detector gain must e increased (and visa versa)
ecause fewer secondary electrons are generated.
Black level is not affected as much. For 5K to 20K magnification work, use a
10 - 20 µ spot size.
Stage control :
Do not adjust the “Z” control. This is set to provide an optimal distance
(10 – 12 mm for secondary electron detector and 20 mm for the EDAX
detector).
Do not force any stage control kno .

Do not handle specimen stu s
with your are fingers.
Contaminates from your fingers
will volatilize in the high
vacuum and contaminate the
final eam aperture and
detectors which in turn will
significantly degrade the image.
The “X” and “Y” controls are approximately centered at 500 X 500 with TILT
at 0 degrees.
Do not adjust the TILT less than 0 degrees nor greater than 90 degrees.
Turning ON the electron beam:
Turn ON the high tension. There should e a “ lip” in the filament current
gauge. Adjust the current to saturation (usually 5-6 clicks). Do not over-
aturate the filament.
Aligning the electron gun (if nece ary):
With a spot size of 500 and minimum magnification, turn up the filament
current until the current no longer rises on the gauge. Adjust the detector
gain to provide a circular illumination. Center this circle on the screen
using the “gun shift” then use the “gun tilt” controls to give the rightest
illumination.
Changing or in erting a new pecimen:
Be sure the filament current and high tension is off and the filament has
cooled for at least 1 minute.
Press the OFF utton on the vacuum control panel.
Press the air utton.
Wait for the specimen cham er door to release and then carefully pull the
stage assem ly out.
Use the 1.5 mm Allen wrench to secure
the specimen stu to the holder. Do not
over-tighten the set screw. It only needs
to e firm.
Push the stage assem ly into the
cham er eing ab olutely sure that t h e
specimen will not hit the EDAX detector.

Press and “release” the AIR utton and press the vacuum ON utton. You
should hear the vacuum pull the door sealed shut.
When the vacuum is ready (10 or less on the vacuum gauge and RED high
vacuum light is off), the electron eam may e turned on.
Shutting down the SEM:
Turn the filament current to zero.
Turn off the high tension y pushing the HT utton and letting it release.
Turn the lack detector gain down 1 turn (clockwise).
Turn off the SE detector (push the utton and let it release).
Turn the spot size to 500 (this is the lowest lens current setting).
Turn the magnification control to maximum (lowest lens current setting).
Turn off the light column switch.
Turn off the “marker” switch.
The SEM can be left in thi etting a tandby mode for the day.
Do not leave the SEM on overnight.
To completely hut down the SEM (overnight or longer):
Press the vacuum OFF utton.
Press the power OFF utton.
Set the cooling water timer to at least 30 minutes to cool the diffusion pump
(quickly turn clockwise past OFF to >30).
If the microscope will not e used again for an extended period (1-2 days or
more), then turn off the master mains switch.
Please e sure that specimens are prepared properly and are free of volatile
su stances. Otherwise, the detector and final pole piece aperture will
ecome contaminated and degrade the SEM performance.