FEG microscope problems

[Pacific GridTech]

Dear colleagues,

A similar experience may help Terje to shoot his
multiple beams problem. I would like to share it with
everyone.

Few years ago, while we were adjusting a new installed
CM200FEG scope which equiped with a Gatan Imaging
Filter CCD, we found a similar problem of multiple
beams. Since the scope was installled inside a room
which is with iron walls arround, the outside
electromaganetic fields were mostly blocked and the
intensity of fields were reduced to a very low level.
Therefore, in our case, the multiple beams problem is
un-likely due to the outside fields.

Eventually, we found the problem is due to an
un-capped port on the ethernet coaxial cable
connector. The CCD camera on the scape is controlled
by a Mac computer and the Mac is connected to local
area network over a coaxial cable. However, the Mac
was connected to a multiple coaxial cable connector
firstly, then the connector connected to ethernet Hub.
One of the port in the multiple coaxial cable
connector is un-covered with a port cap, therefore, it
exposed in air. By capped or un-capped the port, the
multiple beams problem can be removed or appeared
respectively. We still don't know the reason.

I hope Terje could gain enlightenment from it for
shooting his problem.

Wendy Zhang
Pacific GridTech
A high quality Cryo-EM grid provider
3505 Caminito Carmel Landing
San Diego, CA 92130, USA
Tel: (858) 336 8938; Fax: (858) 259 5511
Email: info at grid-tech.com
Web: http://www.Grid-Tech.com/



--- hainfeld at bnl.gov wrote:
> this may not be the right ans, but:
> field emitters have electrons coming off of low work
> function crystal 
> surfaces.  the tip is usually 111 oriented W.  But
> emission comes from the 
> other surrounding planes, and if not blocked will
> focus to multiple beams.
> J. Hainfeld
> 
> At 02:52 PM 5/8/2003 +0800, Terje Dokland wrote:
> 
> >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. James F. Hainfeld  *  hainfeld at bnl.gov
> Brookhaven National Laboratory  *  Biology Dept.  * 
> Bldg. 463  *  Upton, 
> NY  11973   USA
> Tel.  631-344-3372  *  Fax. 631-344-3407
> website:
> http://bnlstb.bio.bnl.gov/biodocs/stem/stem.html
> 
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