All individuals intending to use the electron microprobe or scanning electron microscope for research are expected to take this course. Therefore, enrollment is open to all faculty and graduate students in Anthropology, Biological Sciences, Chemistry, Forestry, Geography, Geology, Physics and Astronomy, and Quaternary Studies. Interested undergraduate students also may enroll with the instructor's permission.
This course is designed to familiarize students with the physical principles underlying electron microbeam analysis and the operation of the Cameca MBX electron microprobe and JEOL scanning electron microscope. Analysis of elements with atomic numbers greater than 10 in multi-element materials and electron imaging will be emphasized.
Upon completion of this course students should be able to demonstrate knowledge of X-ray theory fundamentals, electron-material interaction effects, electron microbeam instrumentation, electron imaging, microprobe and SEM operation, statistics relevant to data collection and analysis, and data reduction methods.
This format of this course will be somewhat open. There will be approximately ten weeks of lectures and 2-to-3-hour laboratories. Some lecture topics may receive increased emphasis depending upon specific student interests. Whenever possible, classroom material will be illustrated through laboratory exercises and demonstrations. Upon completion of this first part of the course, every student will do a class project which will require one day of microprobe usage.
The course will use a set of on-line course notes prepared by the instructor for its textbook. No books on electron microprobe techniques will be placed on reserve. However, students may wish to consult the following texts (in the library):
· Reed, S. J. B., 1993, Electron Microprobe Analysis
· Williams, K. L., 1987, Introduction to X-ray Spectrometry
The course will be divided into the following major sections:
INTRODUCTION presenting the electromagnetic spectrum, the definition of X-rays and a quick survey of X-ray history and applications.
· X-RAY THEORY examining topics necessary to the understanding of the physical principles underlying electron beam analysis. This will include: the energy-wavelength relationship; atomic structure; electron interaction with matter (elastic effects; production of the X-ray spectrum, continuum radiation, characteristic X-rays, satellite peaks, wavelength shifts, secondary and backscattered electrons, Auger electrons, and cathodoluminescence, volume of excitation; primary absorption and excitation potential, and secondary fluorescence).
· INSTRUMENTATION BASICS covering the different subsections of an electron microprobe and SEM and their functioning, including: electron column (electron gun, condenser magnetic lens, multiple aperture system, beam regulator, beam blanker, stigmators and deflector coils, and objective lens); imaging systems (optical microscope, backscattered electron detectors, secondary electron detectors, absorbed current imaging); sample stage; X-ray spectrometers (diffraction of X-rays, spectrometer optics, mechanical layout, analyzing crystals, take-off angle, Rowland circle); X-ray detection (gas-flow and sealed detectors, scintillation detectors, and semiconductor detectors, pulse-height analyzers, single-channel and multi-channel analyzers, WDS vs. EDS detection); computer system; vacuum system (mechanical and oil-diffusion pumps).
· SAMPLES examining sample selection and preparation for analysis.
· IMAGING examining how images are produced, potential image signals, and the basics of image processing.
· STATISTICS providing a quick overview of statistical methods relevant to microprobe analysis. These will include: accuracy and precision, counting statistics, combining errors, homogeneity index, determining optimum counting times, and detection limits.
· QUANTITATIVE ANALYSIS covering different data reduction procedures used in microprobe. These will include: calibration curves; empirical correction coefficients - Bence-Albee; ZAF and PAP.
· INSTRUMENT OPERATION emphasizing the use of the Cameca MBX microprobe and JEOL SEM. Topics covered will include: instrument set-up, instrument procedures; standardization; analytical programs; data reduction and mineral stoichiometry calculations.
Some of these topics will be covered simultaneously in order to allow the students to apply theoretical knowledge to practical operation of the microprobe. For example, the discussion of wavelength shifts will be accompanied by a laboratory demonstration of the effect.
The following criteria will be used to determine the grade that will be received:
· Problem Sets (30 %) - Problems will be assigned during the course to evaluate a student's understanding of the material covered. These will be due one week after they are assigned.
· Laboratory Experiments (30 %) - Whenever appropriate students will use the microprobe to examine specific topics. They will collect data and analyze it as directed in a lab handout. Results are due one week after the laboratory session. Attendance at all labs is mandatory.
· Probe Project (40%) - Students will perform analyses and interpret the results for a project chosen in consultation with the instructor. A short (3-5 page) report summarizing the analytical setup and results will be due before the final day of class. Individual times on the microprobe with the instructor will be scheduled for this project.
The final grade will be determined by dividing the total number of points a student receives by the total possible points, weighting them according to the percentages above, and expressing the result as an overall percentage rounded to the nearest 1% (0.5% will be rounded up). Grades will be assigned as follows: <60% = F; 60-69% = D; 70-79% = C; 80-89% = B; and 90-100% = A.
Regular attendance is expected for both class and laboratory portion of this course. A substantial part of the course involves hands-on use of the microprobe during labs. An excessive number of absences, as determined by the instructor, will result in a grade of F. Plagiarism or any other form of cheating will result in an automatic grade of F. If there are exercises where students may cooperate, these will be specifically announced. There will be no "make-ups" on any tests or exercises, unless they are arranged with the instructor in advance. All materials submitted for evaluation (exercises, projects) must be legible. Some students may wish to type their work.