OSU Electron Microprobe Laboratory

The OSU JEOL electron microprobe is an analytical instrument that images and analyzes materials stable in a vacuum environment. This machine can identify elements present in a mineral as small as 5 thousandths of a millimeter. Electron microprobe analysis is non-destructive and is used for detailed analytical study of important features in rocks, including compositional zoning of individual grains or reaction zones between grains.

Submitted samples will be analyzed on a contract basis (i.e. lab personnel will do the work).
Visitors are invited to work in the lab to work with lab personnel.
Visitors are invited to work in the lab to design and do the work yourself.
Training Session (short course) is offered.

A webpage details the user fee structure http://blogs.oregonstate.edu/microprobe/pricing/. We have two classes of users (internal and external) divided into assisted and unassisted costs, as well as sample preparation and optional optical characterization fees.

As our lab is new (~2 years), machine time is often available for funded research and lab visitors. In the Spring, we teach a class in electron microprobe analysis.

The machine has remote conferencing software in which we can transfer digital image, maps and spectra by directly linking two computers. Our EDS software (Evex) can make Quicktime movies of EDS analysis sessions.

*The lab does not provide thin section preparation. We can analyze one-inch electron microprobe rounds and standard size thin sections, and can make and analyze polished grain mounts for analysis if necessary.
*The lab has the capability to make in situ ion microprobe mounts as well. For example, we can identify minerals suitable for geochronology, document their locations, create ion microprobe mounts, and document and coat those, thus arriving at an ion microprobe facility with 100% of the sample preparation complete.

The OSU JEOL 733 is equipped with four spectrometer crystals (LIF, PET, TAP, LDE2), back-scattered and secondary-electron scanning capability, and an energy-dispersive system consisting of a detector and image-analysis software.

The instrument is also capable of obtaining X-ray element maps for elemental distributions within materials. The X-ray spectrum used in quantitative analysis is generated by the sample in response to a finely focused electron beam striking the surface. X-ray intensities are measured by either using wavelength-dispersive spectrometry for quantitative data or energy-dispersive spectrometry for qualitative mineral identification. The OSU electron microprobe lab has 68 mineral standards (SPI mounts 02758-AB, 02753-AB).

The machine uses Evex Analytical Microanalysis software for the EDS capability and SAMx Microprobe Analysis software for the WDS capability. Both software packages are powerful, flexible, and incorporate the latest developments in electron microprobe analysis. See www.evex.com or https://www.sams-xrays.com/smak for more information or read below.

EVEX software allows the machine to acquire EDS spectra in 25 separate windows, both automatically and manually identify and calibrate EDS peaks, export spectra using TXT, JPG, or BMP formats, as well as perform spectral operations, including adding, subtracting, multiplying spectra, and overlaying other spectra for comparison. This software is capable of semi-quantitative analysis by using both standard and standardless analysis. We can acquire images with as much as 4K by 4K pixel resolution and 12-bit gray levels in point, line, and frame acquisition modes, can export images in over 30 different types of formats, including TIFF, BMP, or JPG, has brightness, contrast, and gamma palettes, has variable preview, scan sizes, and dwell times. The imaging software can also analyze by histogram equalization, and can smooth, sharpen, filter, crop and zoom.

The machine can element map in one-click by labeling the region of interest on the spectrum and pressing the map button. Indexed mapping can generate a spectrum at every pixel as well as create real-time EDS analyses at every pixel. We have unlimited simultaneous map acquisition, and the capability of overlapping maps over SE or BSE images. Map operations include adding, subtracting, multiplying (etc). We can export images in over 30 different types of formats (TIFF, BMP, JPG, etc).

An additional capability is 3-D element mapping, where we can represent the element maps as 3-D rotating images. The software has the capability to count particles identified by the user, as well as automatically identify them by size, % area, and EDS. Because the limit of the magnification of the electron microprobe is 40X, we use image stitch, where we assemble multiple pictures into one.

One new development is stereo imaging, where two images are combined to create one 3-D picture. With the help of 3-D glasses, the image is brought to life. The software can then be used to profile areas and conduct volume analyses. The 3-D imaging capability allows data to be represented in a visually exciting way. We can make movies of sample traverses, scans and EDS spectra as they are created using Quicktime, with both text and video annotation.

SAMx WDS software is capable of statistical analysis, area peak factor calculation, quantitative peak integration and peak interference correction. A stage program is included for storing points, lines and grids for later use by qualitative, quantitative and positioning programs. An intuitive graphical interface allows the user to save all information necessary to define a standard, and a built-in interference routine can detect all potential element line interferences up to 8th order. The software allows automatic beam current control, which ensures precise read and writes from microamps to picoamps as well as current regulation. This capability is indispensable for achieving accurate analyses. A sophisticated graphical package displays and manipulates acquired data, including spectrometer scans, quantitative beam and line scans and PHA scans. Users can also run the line scans and standard and unknown compositions unattended.

Class demonstrations are available for undergraduates.
Class demonstrations are available for K-12.
Undergraduate student research projects are invited.
Graduate student research projects are invited.

*The OSU electron microprobe is a key part of a NSF New Frontiers: Research Experience for Undergraduates in the Space and Planetary Sciences site (NSF Award #0138942). In this program, twelve undergraduate students are placed into research groups which involve chemists, biologists, geologists, physicists and mechanical engineers who are interested in space and planetary research. Undergraduates can apply to this summer program (see http://spacecenter.uark.edu/97.htm).

*GEOL5263 is a lab-oriented practical course for future users of the OSU electron microprobe. The goal is to provide training for those interested in using the electron microprobe and to familiarize the operator with the basic principles of X-ray microanalysis. By the end of the class, students should be able to operate the electron microprobe efficiently and independently. Enrollment is limited to 8 students per semester, and includes primarily graduate students. Undergraduate students would be allowed to enroll with instructor permission, and most likely would have a research project with a topic that directly pertains to the course.

The lab has been funded by OSU institutional support, an OSU College of Arts & Sciences award, and a grant from the Arkansas-Oklahoma Center for Space and Planetary Sciences.