This project is to upgrade the Earth & Environmental Science's Electron Microprobe Laboratory (EMPL) housing a Cameca SX-100 Electron Probe Microanalyzer at Rensselaer Polytechnic Institute (RPI). The upgrade involves the installation of a new computer workstation running Probe for EPMA and Probe Image interfaced with the instrument. This upgrade was justified on the basis of three main criteria: First, examples were provided of major limitations imposed by the current vendor-supplied software package (Cameca's Peak Sight) that may be overcome using software available from Probe Software, Inc including (1) new algorithms to improve minimum detection limits, precision, and accuracy; (2) superior time-dependent intensity corrections; and (3) improved X-ray mapping capabilities. Second, a description was presented of ongoing and future projects that have compelling scientific merit and require characterization using a state-of-the-art electron microprobe. Third, this facility has had an excellent track record of high quality science with current instrumentation, a successful and sustainable maintenance and administration plan, numerous collaborative research efforts, and a highly diverse user base. An upgraded Electron Microprobe Laboratory at RPI will benefit both the larger Rensselaer Community and the broader Upstate New York/New England Region by enhancing current capabilities as a regional facility.
The EMPL has been and will continue to be open to the public along with undergraduates, graduate students, post-docs, research faculty, and professors at Rensselaer and elsewhere. In addition to providing analyses free of charge to undergraduates completing various projects, this facility participates annually in the ExxonMobil Bernard Harris Summer Science Camp, a free two-week program for fifty middle school students (grades 6-8) from the New York Capital Region designed to instill a life-long interest in math and science. This upgrade will greatly enhance the learning experiences of students, visitors, and new users alike thanks to the fully-integrated, user-friendly nature of Probe for EPMA which visually emphasizes important considerations (background models, time-dependent intensity corrections, wave scans, etc.).
One of the primary analytical instruments for materials analysis is the electron microprobe. The Department of Earth and Environmental Sciences purchased a new electron microprobe with the help of NSF funds in 2002. The instrument has been a mainstay of geochemical research for the 12 years since its installation. A major enhancement of new instrumentation is the seamless integration of various electronic and mechanical parts through sophisticated software to align the instrument, scan for specific elements, drive spectrometers, and position the stage accurately. Indeed, many modern applications of electron microprobe analysis would be impossible without such computer automation. The software originally supplied with our current electron microprobe had significant limitations in the range of analyses that it could perform. The instrument itself is performing at peak performance but our analytical capabilities are limited because of restrictions of the earlier software. The purpose of this proposal to NSF was to purchase an upgrade to the software so that new analytical capabilities could be developed. This upgrade to the electron probe facility was designed to enhance research not only among the geochemists and geologists in our department but for researchers in other branches of material science at Rensselaer as well as for a range of users of the facility from other institutions. The two software packages that we purchased are called Probe for EMP and Probe Image and are product of Probe Software, Inc. The software has been delivered and installed and is now in routine use in our electron probe facility. There have been a number of specific applications that are significantly improving our research capabilities. These include: (1) The analysis of trace elements with lower detection limits. Our old software was capable of analyzing trace elements with detection limits of a few tens of parts per million (ppm). The new software has improved this to better than 5 ppm detection limit in optimal situations. (2) Improved throughput for major element analysis. Measurement of background in spectral analysis often is as time-consuming as measurement of the peak. The new software has modules to model the background as a function of the mean atomic number of the material and employ this through the analysis workflow. This capability alone nearly doubles the analysis throughput. (3) In many natural materials, the electron beam of the microprobe damages the sample to the extent that the apparent concentration of an element changes with duration of analysis. The new software has significantly improved time-dependent intensity corrections enabling much more accurate analysis of, for example, fluorine in apatite (e.g. teeth). (4) Large area compositional imaging is greatly enhanced. A principal objective of geochemistry is to first determine the distribution of elements within the materials studied. We have employed X-ray mapping for this capability for two decades but with severe limitations due to computer memory and graphic card limitations. The new software overcomes these limitations enabling significantly more rapid and through characterization of samples. These and other capabilities of the new software will enable state-of-the-art science to be performed on this instrument for the next decade and beyond and as such is an excellent investment.
