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, 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 >>> > >