EPMA (Electron Probe Micro Analyzer)

EPMA Details
1. Name of Instrument :Electron Probe Micro Analyzer (EPMA)
2. Model/make :CAMECA -SX-100 model
  3. Principle

The basic principal involved is, an electron beam is applied on a polished solid surface of the sample causing the emission of characteristic X-rays, are diffracting by crystal involving the principle of Bragg’s Law (nl = 2d Sin q). Each atomic element emits specific and identical wavelength of characteristic X-rays that are focused onto a detector where they are counted. From the intensity of the characteristic X-rays the concentration atomic element in the sample are calculated, and proper matrix corrections are applied.

  4. Description

The basic principal of the instrument involves that, each atomic element emits specific and identical wavelength of   X-rays i.e., the application of an electron beam on a polished solid surface of the sample causes the emission of characteristic X-rays.  The X-rays are then deflected in  a Wavelength  Dispersive  Spectrometer by a diffracting crystal that focuses  each  precise wavelength onto a detector, where the intensities of the element are counted. The deflection of X-ray of individual elements by diffracting crystal involves the principle of Bragg’s Law (nl = 2d Sin q). Then, from the intensity of the characteristic X-rays, the concentration of the atomic element of the mineral are calculated, after applying proper matrix corrections.

 5. Applications

EPMA applications have special advantage, as they involve non-destructive in-situ analysis of minerals in polished thin sections, retaining textural relationships among coexisting minerals. It allows qualitative and quantitative analysis of individual mineral grains a few micrometers in diameter. The elements can be qualitatively or quantitatively mapped. Incorporation of a coaxial light optical microscope in the electron optics provides the familiar optical image capability used by mineralogists and geologists for identification of mineral grains and textural features of interest for chemical analysis. Fine-scale mineralogical features, such as zoning in minerals, minute inclusions, and exsolution lamellae can be measured because of the small analytical excitation volume. The instrument can be used to generate back scattered and secondary electron images. The geological application is even extended to date the minerals like monazites with this instrument. Material science applications are even more varied, from thin film semi-conductors to photonics materials to super conductors. The other applications include measurement of cathodoluminescence to characterization of minerals; chemical diffusion studies at materials interfaces. It has also lot of applications in other branches of sciences too.

 6. Material needed for analysis

(i) Very good fine polished Thin Sections of 48 x 30 x 2 mm size.

(ii) High quality epoxy mounted polished sample sections of 25 mm diameter.