FEG microscope problems

[Bruno Klaholz]

Dear Terje,


indeed, a field canceling system could help.
But first have a site survey done which will tell you whether you have any 
magnetic field at all, before buying a field canceling system.
The point is that you should get only one single spot, even at very high 
mag. (200.000x or so) which should not vibrate...
Concerning magnetic fields:
- if you have a constant field (like from an NMR group...) this will be 
usually canceled very well.
- if you have a dynamic field, is depends on the frequence. For the ones 
generated by electric cables (lights etc.!), you have about 50-60Hz, so 
these ones are canceled well by a dynamic field canceling system.
- if you have very low frequencies (~1Hz electromagnetic waves) nothing 
will help I g think and its better to move somewhere else...

If you install a field canceling system, put the sensor close to the C2 
apperture or so,
on the side of the column where you have the strongest field.
For this you should probably do a site survey first.

Hope it helps,

Bruno




>We recently had a new JEOL 2010FEG microscope installed. However, after 
>installation, we find that there is not one, but four to six beam spots!
>
>The technician says it is due to magnetic interference. He also claims 
>that it has no effect on resolution, and that may be true with respect to 
>gold or graphite, but I'm sure it can't be very good for coherence and 
>phase contrast, and hence the whole purpose for having an FEG is lost!
>
>Has anybody else had such experience with an FEG microscope? Was it due to 
>magnetic interference, and was there a way to fix it? We will try a 
>magnetic field canceler in a few weeks time. Is this likely to work? 
>Suggestions are welcome, as I am not too happy to pay for the microscope 
>until this problem has been solved!
>
>terje
>
>--
>------------------------------------
>Dr. Terje Dokland
>Senior Scientist
>Institute of Molecular and Cell Biology  <--- NOTE NEW ADDRESS !
>1 Research Link, A*STAR Building
>Singapore 117604
>Phone: 65-6872 7405  Fax: 65-6872 7007
>E-mail: dokland at imcb.nus.edu.sg
>
>"Convictions are greater enemies of truth than lies"
>                                 F. Nietzsche
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Dr. Bruno Klaholz
Département de Biologie et Génomique Structurales
Institut de Génétique et de Biologie Moléculaire et Cellulaire
IGBMC - UMR 7104
1, rue Laurent Fries
BP 10142
67404 ILLKIRCH CEDEX
FRANCE

Tel. from abroad: 0033.390.24.47.98
Tel. inside France: 03.90.24.47.98
Fax from abroad: 0033.388.65.32.76
Fax inside France: 03.88.65.32.76
e-mail: klaholz at igbmc.u-strasbg.fr

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