General Precautions
UltraScan Use
r
’s Guide Reference Series Rev 1.0
5-3
beam intensity (above 30,000 counts in binned by 1 mode and 60,000 counts in
binned by 2 and higher modes). If you have no saturation with a short exposure,
then there is no danger. You can then increase the exposure time and still not
harm the scintillator as it is the beam intensity on the scintillator that causes the
problem and not the accumulated signal in the CCD.
It is recommended to use beam stop to block the central spot when acquiring
SAED diffraction patterns.
If you think you have damaged the scintillator , take an unprocessed image of
uniform illumination. If the spot turns out dark, you have damaged the
scintillator! If it is bright, spread out the beam and set the illumination so you
have about 10,000 counts/sec (in binned by 2 mode) and switch the shutter
switch on the controller to Open. Expose the scintillator for 3 min, switch back
to Auto, and take another picture. The bright area should be gone and the
scintillator should operate normally.
•
Warm the scintillator if oil contaminated.
Check the scintillator for oil contamination by acquiring an image at low kV
(about 60 kV) to put in evidence surface’s contaminations. If you have a clean
vacuum in the camera chamber area you may not need to do any warming for
several months. But if you have backstreaming from your diffusion pump, you
will need to do it more frequently. The camera should only be warmed for 15
hours or overnight, but not longer. If the camera is used sufficiently without
warming and there is contamination, the electron beam can harden the trapped
oil making the scintillator difficult to clean.
Switch the Peltier cooler to the “Warm” position.
It is OK to run the Peltier cooler in the warm position overnight,
but do not run it when the camera is at air pressure or if the cooling
water is not flowing.
Check vacuum system.
If oil accumulates even with regular warming of the scintillator, it
is recommended that the vacuum system be checked.
Examine the surface of the scintillator.
If the surface of the scintillator becomes dirty or scratched, ship the
camera to Gatan for service. Do not attempt to clean the scintillator
yourself as damage can result.
5.1.3 Fan Filter
The controller’s fan filter (see Figure A7 in Appendix 1) needs to be washed
every six months.
To clean the filter:
