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April 2007

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Subject:
From:
Ron Rasch <[log in to unmask]>
Reply To:
JEOL-Focused Probe Users List <[log in to unmask]>
Date:
Wed, 11 Apr 2007 18:06:53 +1000
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*

Hi,

thanks for all the replys. Yes, I see all these problems which is why  
I always defocus and never raster. Just checking to make sure I was  
standing my ground on firm ground. You know, new users to the lab  
saying "we always did it this way before...". Thanks for letting me  
check with you, I feel confident that I haven't missed something.

cheers,
Ron



AK: I sometimes use a defocussed beam, but for the reason mentioned by  
Andy Buckley I stay away from rastering. The JEOL 8200 has a "beam  
diameter" parameter in its EOS setup, which is fairly accurate judging  
from materials that show the "burn" spot.......

PH:  I just have to add my 2 or maybe 4 cents into this discussion.
         Cent 1.  Rastering while analyzing is the worst possible way to
do a "bulk" analysis of inhomogeneous materials due to the "flag pole
effect" (my term or I may have heard it a long time ago).  The beam is
not rastered evenly.  A delay is programmed into the raster at the
beginning of each horizontal line to compensate for hysteresis in the
scanning coils.  This produces a "flagpole" of extra dwell time at the
left side of the raster........

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