The electron probe microanalyser (EPMA) permits the nondestructive, major and trace element analysis of small volumes (3~4µm diameter) of solid materials in situ. Spatial control of analyzed points in the sample is assured with precise movement of the sample, and a range of optical and electron imaging techniques, which makes the instrument ideal for studies of mineral composition or identification, mineral zoning, chemical reactions, etc.
The electron microprobe works on the principle of identifying and measuring x-rays, which are characteristic of the sample's composition. The technique is born out of the fact atoms are ionized when a beam of high energy electrons have enough energy to remove inner shell orbital electrons, which releases electromagnetic radiation, or x-rays, when outer orbital electrons fill the electron vacancy. If the x-rays' energy is determined relative to either energy or wavelength, and the intensity is also measured, then the element is identified and its abundance is also measured as elemental mass fraction.
The Electron Probe Microanalytical Facility at Memorial University is centered around a 1991 Cameca SX-50 microprobe. Our Cameca is configured with three wavelength discriminating (WD) spectrometers and an Oxford Instruments energy dispersive (ED) detector. All is controlled by Samx software, specifically using XmasPlus for WDX and IDFix for simultaneous EDX, and Samx's Himax and Maxview softwares for imaging applications.
The ED x-ray detector enables quick qualitative and quantitative analysis. It is used for semi-quantitative reconnaissance analyses of unknown materials, and for the accurate and precise measurement of major element concentrations in many samples. The WD x-ray spectrometers allow the precise and accurate measurement of major and minor elements at concentrations typically as low as 0.01 wt%.
Researchers and Personnel
Ms. Wanda Aylward, principle investigator in charge of microprobe facility.
phone: (709) 864-3076/6105