[3dem] Arching in the gun chamber

[kunihiro uryu]

Hi Valorie,

Thanks for your swift reply. We do experience shortage of tip life (of
Lab6). Our service engineers made sure high vacuum level and exchanged many
parts, including insulating oil, IGP and the gun cable. They even tried a
new HT generator. The chamber is practically new by now. It is still a
tough arching to get rid of. Recent serious cleaning of chamber made a
significant difference. It is now less frequent, but we still experience
time to time.

I think that something, possibly vacuum leak and/or overtime accumulation
of contamination in the chamber, must have led the chamber susceptible
to arching. Repeated arching caused more contamination and exacerbated the
whole situation. How can we get rid of arching completely? Any suggestions
would be appreciated.

Regards,
Hiro

------
Kunihiro Uryu, Ph.D.,
Research Assistant Professor
Director of Electron Microscopy
Resource Center (EMRC)
RRB Rm120
The Rockefeller University
1230 York Ave., Box 230
New York, NY 10065

On Fri, Jul 17, 2015 at 9:25 AM, Bowman, Valorie D <vdb at purdue.edu> wrote:

>  Dear Hiro,
>
> It means the vacuum is not good in the FEG.  You may have a leak.  Check
> the IGP value in the FEG and ask your service engineer what values are safe
> to use on your microscope.
>
> It will destroy your filament!  If you keep using it this way one of the
> arcs will "blow" (short out) the filament and you will have to have it
> replaced.
>
> And yes, it will affect data quality.  It means your FEG will not be
> giving you the coherent beam you want.
>
> Hope this helps,
>
> Valorie
>
>  Valorie Bowman
>
> vdb at purdue.edu
>
> Senior Research Electron Microscopist
> Purdue Cryo EM Facility
> Purdue University
>   ------------------------------
> *From:* 3dem [3dem-bounces at ncmir.ucsd.edu] on behalf of kunihiro uryu [
> kuryu at mail.rockefeller.edu]
> *Sent:* Friday, July 17, 2015 8:48 AM
> *To:* 3DEM Mailing List
> *Subject:* [3dem] Arching in the gun chamber
>
>   We are experiencing arching in the gun chamber. Has anyone experienced
> it? If so, did it affect data quality? How did you fix it?  Many thanks
> in advance.
>    Regards,
> Hiro
>
>  ------
> Kunihiro Uryu, Ph.D.,
> Research Assistant Professor
> Director of Electron Microscopy
> Resource Center (EMRC)
> RRB Rm120
> The Rockefeller University
> 1230 York Ave., Box 230
> New York, NY 10065
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ncmir.ucsd.edu/pipermail/3dem/attachments/20150717/c5cb773c/attachment.html>