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Electron Microprobe Lab, University of Minnesota

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*

All,
My experience (only about two years) with a LaB6 source on a JEOL 
6400 was that the resolution improvement was only around a factor of 
two over W. We swapped back and forth for a while but ended up on W 
for beam stability. In fact, we saw a much more significant 
improvement in resolution by carefully cleaning and re-aligning the 
column mechanically on that now defunct instrument.

Note that JEOL also sells a FEG gun (8500) for high current 
analytical work and low current high resolution imaging. Cameca's 
stability specs on the LaB6 are the same as for W (last time I checked).

The other advantage of both the LaB6 and FEG is that they can image 
at low keV better than W.
john

At 10:42 AM 9/27/2007, you wrote:
>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
>
>
>
>*
>
>Probe folks,
>
>Today I received the following message from one of the professors in
>our department:
>
>>Ellery,
>>
>>I was just at a meeting where a colleague was telling me about his
>>SX-100 microprobe and the amazing improved spatial resolution it
>>gets for both imaging and quantiative analyses owing to the LaB6
>>source. It's my understanding that JEOL sells the 8200 with an
>>option of a LaB6 or tungsten filament source.  Do you know if JEOL
>>will retrofit 8900s with Lab6 and if so, how much it costs?  The
>>fellow with the SX100 says that Cameca charges something like $10k
>>extra for a LaB6 source on the SX-100...
>>
>>Marc
>
>Is such a refit possible or feasible?  I know it is easy to go from
>LaB6 to W filament, but it seems harder to go the other way.  I
>believe that we'd need an ion pump at the top of the column for LaB6,
>but would a turbo pump need necessary too or are diffusion pumps
>okay?  Are the electronics, heating system, etc. the same or not?
>
>I am also curious if anyone is currently running or has recently run
>a LaB6-outfitted machine.  Are the concerns about beam stability
>valid, or is the issue overblown?  What is the typically stability in
>your experience?  What are current opinions about LaB6?  Having never
>used a LaB6-equipped microprobe, I don't have any first-hand
>experience or observations on which to draw.
>
>Any facts, observations, opinions, wild speculations, or hearsay are
>welcome.
>
>Best,
>Ellery
>
>--------------------
>Ellery E. Frahm
>Research Fellow & Manager
>Electron Microprobe Laboratory
>University of Minnesota - Twin Cities
>Department of Geology & Geophysics
>Lab Website: http://probelab.geo.umn.edu
>Personal Website: http://umn.edu/~frah0010