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Electron Microprobe Lab, University of Minnesota
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*
Jens,
Yes, that can be useful. With WDS one can always to a WDS scan too.
eric
On Aug 29, 2006, at 8:10 AM, Jens C. Andersen 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]
>
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> On-line help and FAQ: http://probelab.geo.umn.edu/listserver.html
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>
>
> *
>
> Hi Eric.
>
> I agree, and with wavelength dispersive spectrometers there is
> rarely any need for more than 15kV. On the energy dispersive
> systems, in contrast, there are always the elusive questions that
> are most easily answered by excitation of the K-spectrum by higher
> acceleration voltages. Is it P or is it Zr? Is it Mo, Pb or S?
>
> Jens.
>
>
> ----- Original Message ----- From: "Eric J Essene 1"
> <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, August 29, 2006 12:41 PM
> Subject: Re: [PROBE-USERS] EBSD question: what kev is good?
>
>
>> 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
>>
>>
>>
>> *
>>
>> Jens,
>> 15 kV suffices to excite characteristic X-rays for all 92
>> elements (and beyond) by using L and M lines, of course. The
>> only problem is that the intensity of these lines is not as good
>> as they should be without using higher current and/or voltage.
>> eric
>>
>>
>> On Aug 29, 2006, at 4:32 AM, Jens C. Andersen 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
>>>
>>>
>>>
>>> *
>>>
>>> Hi John.
>>>
>>> Here we have a setup with a JEOL 8200 electron microprobe and a
>>> JEOL 5400 low-vacuum SEM. We generally try to balance our
>>> preferred acceleration voltage to where we get maximum benefit of
>>> the increased x-ray intensity and the high energy end of the x-
>>> ray spectrum without having to correct for too much
>>> "overvoltage" in the matrix correction procedures.
>>>
>>> On the microprobe we work with 15kV on most materials. On rare
>>> occations, we use 20 or 25 kV for special applications, where the
>>> excitation of a specific high energy line is essential. On the
>>> low- vacuum SEM we have too many variables to do fully
>>> quantitative work (notably working distance, beam current, air
>>> pressure, coating thickness, specimen surface roughness and
>>> orientation). We don't have a beam current detector and our
>>> software does not allow us to specify any other parameters than
>>> the kV for the matrix correction. To do fully quantitative work,
>>> you will need to work on a polished surface, and need some way
>>> of measuring the beam current, and need to fix the working
>>> distance, coating thickness, and air pressure.
>>>
>>> Despite the shortcomings of our SEM, our system works pretty
>>> well in a semiquantitative mode at a fixed kV for a measured set
>>> of standards, provided that the results are normalised to 100%.
>>> We have observed no systematic variations with changing
>>> pressure, beam current, coating thickness, or working distance
>>> for elements from sodium and heavier using this method, and our
>>> precision on a 100s live count time is good enough for student
>>> work and exploratory analysis of materials that cannot be
>>> prepared for the electron microprobe (mineral coatings, soil
>>> grains, archaeological specimens, paint fragments etc.). I would
>>> be cautious with fluorine on the low-vacuum setting. For
>>> analysis on the SEM we work at 20kV, which excites the K-
>>> spectrum up until around Zr. There appears to be little benefit
>>> in a further increase to 25kV.
>>>
>>> I hope this helps.
>>>
>>> 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
>>>
>>> ----- Original Message ----- From: "John Fournelle"
>>> <[log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Tuesday, August 22, 2006 7:53 PM
>>> Subject: [PROBE-USERS] EBSD question: what kev is good?
>>>
>>>
>>>> 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
>>>>
>>>>
>>>>
>>>> *
>>>>
>>>> We have acquired a nice new SEM (W filament, variable pressure
>>>> Hitachi S3400) whose function principally is quality CL imaging
>>>> (Gatan PanaCL/F), and EBSD (HKL) work.
>>>>
>>>> We have a question for labs out there with more EBSD experience
>>>> under their belts than we do: have you determined an optimal
>>>> keV setting, for any/all of your work? (we are doing geological
>>>> work)
>>>>
>>>> It seems to me that you don't want to go to higher keV than
>>>> necessary as the scattering will increase (though the effective
>>>> backscattered, oops forescattered electron signals that are
>>>> relevant may only be those from the first events near the
>>>> surface, suggested by Prior [1999]) and the spatial resolution
>>>> will decrease (though I am not convinced about this) -- or
>>>> does going to high keV improve the signal generated on the
>>>> phosphor screen and thus improve the Kukchi line
>>>> discrimination? Clearly having significant counts (=high enough
>>>> current) is probably the most important factor, but given that
>>>> is not a problem, would say 30 keV yield better results vs 15 keV?
>>>>
>>>> thanks.
>>>>
>>>> John
>>>> --
>>>> ========================================================
>>>> John Fournelle, Ph.D. office: (608) 262-7964 cell:
>>>> (608) 438-7480
>>>> Cameron Electron Microprobe Lab lab: (608) 265-4798
>>>> Dept of Geology & Geophysics fax: (608) 262-0693
>>>> University of Wisconsin home: (608) 274-2245
>>>> 1215 West Dayton St. email: [log in to unmask]
>>>> Madison, WI 53706 amateur radio: WA3BTA
>>>> Personal http://www.geology.wisc.edu/~johnf/
>>>> Probe lab http://www.geology.wisc.edu/~johnf/sx51.html
>>>> Probe Sign Up Calender: http://www.microscopy.wisc.edu/cgi-bin/
>>>> calendar/microprobe/calendar.cgi
>>>>
>>>> "The first rule of all intelligent tinkering is to save every
>>>> cog and wheel." -- Aldo Leopold
>>>>
>>>> "For a successful technology, reality must take precedence over
>>>> public relations, for Nature cannot be fooled." -- Richard
>>>> P. Feynman
>>>
>
>
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