Mac wrote:
The image of our Amray SEM has a horizontal band across the center
third of the image which is slightly out of focus. The top and bottom
thirds are fine. This machine, while being fairly old, is new to our
institution and I believe some of the maintenance practices have
lapsed. I was wondering if it was possible that a weak filament or
contaminated optical column or dirty apertures could cause a problem
like this.

Any advice would be appreciated.

Thanks.
Gary

Is this at TV-Scan rate and Slow scan too ! What is the specimen being
examined, This is behaving like a Charging artifact. Try another type of
specimen, Sounds more like a specimen charging problem to me. What is
the Accelerating Voltage. Dirty Column and apertures usually just cause
astigmatism problems


Yukio YANO

Retired SEM Tech.