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June 2007

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Subject:
From:
Ron Rasch <[log in to unmask]>
Reply To:
JEOL-Focused Probe Users List <[log in to unmask]>
Date:
Thu, 7 Jun 2007 16:54:55 +1000
Content-Type:
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JEOL Probe Users Listserver

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Electron Microprobe Lab, University of Minnesota

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*

Hi Jens,

A shame about your iced up EDS detector; very annoying for light  
elements and L lines.

I believe you cannot warm up a SiLi EDS detector under power, but I  
believe it is OK to warm up a SiLi EDS detector if it is not under  
power. I have done it myself a few times with success. My general  
procedure is:

To warm up EDS:
(A) Turn OFF the power on the EDS detector control box. I turn off  
everything that is connected to the detector, the one that supplies  
the HV bias is the most important.

(B) After a suitable pause, I carefully unplug all the leads and  
connectors to the EDS detector unit itself. Mine has a multi-pin plug  
and a BNC (HV) plug. I use electrical tape/electrical boxes to secure  
and insulate all the loose bits and bobs.

(C) Then let the EDS detector warm up slowly. This may take a few days  
or more. I put up signs saying "DO NOT FILL EDS DETECTOR - DO NOT  
CONNECT TO POWER" etc. Some people blow out/warm up the LN2 from the  
detector with air, but this can be dangerous if done too vigorously,  
as it can shower the whole lab with LN2. I usually take the lid off  
the EDS detector to speed up the warming. I also tie some cloth around  
the outside of the dewar to catch the condensate. I have always left  
my detector connected to the SEM and under vacuum.

(D) When the detector is warm, then make sure it is dry inside the  
dewar. Ice inside the dewar causes noise. The ice on the detector  
should now be gone. I clean out any solid debris from the dry dewar.

To cool down EDS:
(E) Fill the EDS detector dewar with LN2, and let it cool down for at  
least two hours. Top up the LN2 after one hour just to make sure it  
has enough LN2.

(F) After you are sure the EDS is cold, and have double checked all  
the power sources are still off, then reconnect all the plugs and  
leads to the EDS detector.

(G) Turn on power to the EDS control box.

(H) Check and calibrate. I use copper (a Cu TEM grid) at 20kV with a  
20-30% dead time. In my system the Cu L line should be more than twice  
the Cu K line.

A few words of caution:
Please use all care and common sense. Remember I have not seen your  
system. Some electrical components may still hold a charge after  
disconnecting. There may be local electrical licencing issues. Be  
aware of the safety issues with liquid nitrogen, cryo-burns and the  
displacement of oxygen.

Finally, when I worked out my plan of attack, I described the detail  
of what I wanted to do and sent it to the local EDS agent. They read  
it and offered their opinion and approval before I proceeded.

I hope this helps - at least as a starting point.

cheers,
Ron



Quoting "Jens C. Andersen" <[log in to unmask]>:

> JEOL Probe Users Listserver
>
> Moderator: Ellery Frahm, [log in to unmask],
> Electron Microprobe Lab, University of Minnesota
>
> Post a message: send your message to [log in to unmask]
>
> Unsubscribe: send "SIGNOFF PROBEUSERS" to [log in to unmask]
>
> On-line help and FAQ: http://probelab.geo.umn.edu/listserver.html
>
>
>
> *
>
> Dear colleagues.
>
> I'm looking for information on how to safely de-ice an EDS detector.  
>  The detector is of the lithium drifted silicon detector type that   
> cannot be brought up to room temperature.
>
> Any advice is appreciated.
>
> Thanks,
>
> Jens
>
>
> Jens C. Andersen
> Camborne School of Mines
> School of Geography, Archaeology, and Earth Resources
> University of Exeter
> Cornwall Campus
> Penryn, Cornwall
> TR10 9EZ
> United Kingdom
> Tel. +44 (0)1326 371 836
> Fax. +44 (0)1326 371 859
>
> http://www.exeter.ac.uk/cornwall/csm
>
> Visit the virtual Skaergaard intrusion at http://www.skaergaard.org

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