[3dem] Arching in the gun chamber

[Schwartz, Cindi (NIH/NIAID) [C]]

We had a T12 with this issue and lots of contamination in the chamber. There was this little plug looking piece that has a special tool to remove it that sits under the chamber, in the column. That was very dirty and we replaced it with a new one and all is well.

Cheers,
Cindi
_______________________________________
Cindi L. Schwartz
Electron Microscopist
Rocky Mountain Laboratories/NIAID/NIH
903 South 4th Street
Hamilton, MT 59840
(240)669-5473
Cindi.Schwartz at NIH.Gov<mailto:Cindi.Schwartz at NIH.Gov>

From: kunihiro uryu <kuryu at mail.rockefeller.edu<mailto:kuryu at mail.rockefeller.edu>>
Date: Friday, July 17, 2015 at 8:59 AM
To: "Bowman, Valorie D" <vdb at purdue.edu<mailto:vdb at purdue.edu>>
Cc: 3DEM Mailing List <3dem at ncmir.ucsd.edu<mailto:3dem at ncmir.ucsd.edu>>
Subject: Re: [3dem] Arching in the gun chamber

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<mailto: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<mailto:vdb at purdue.edu>

Senior Research Electron Microscopist
Purdue Cryo EM Facility
Purdue University
________________________________
From: 3dem [3dem-bounces at ncmir.ucsd.edu<mailto:3dem-bounces at ncmir.ucsd.edu>] on behalf of kunihiro uryu [kuryu at mail.rockefeller.edu<mailto: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

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