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August 2006

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Date:
Tue, 29 Aug 2006 21:52:10 -0400
Reply-To:
JEOL-Focused Probe Users List <[log in to unmask]>
Subject:
From:
Eric J Essene 1 <[log in to unmask]>
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JEOL Probe Users Listserver

Moderator: Ellery Frahm, [log in to unmask],
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]
>
> Unsubscribe: send "SIGNOFF PROBEUSERS" to [log in to unmask]
>
> On-line help and FAQ: http://probelab.geo.umn.edu/listserver.html
>
>
>
> *
>
> 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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