"Engineering the Application of Materials"

X-Ray Generation Simulation

This java based application simulates the generation of x-rays in the scanning electron microscope. The scanning electron microscope uses a beam of high energy electrons to illuminate the surface of a material. The microscopist can only see an image of the surface of the material, however, x-rays are generated from material on and below the surface. The high energy electrons enter the material and ricochet around as they bounce off atoms. Sometimes the electron can ionize an atom and produce an x-ray. The x-rays generated in the material have different energies depending on the particular atom from which they were generated. Each x-ray generated by the electron results in a loss of energy to the electron and eventually, it runs out of steam and cannot generate anymore x-rays. By counting the x-rays of each characteristic energy we can ascertain the chemical composition of the material. However, we must be careful because the material underneath the surface may not be the same as that at the surface.

This simulation allows you to see what the effect of changing the surface and underlying material has on the relative proportions of x-rays collected by the x-ray spectrometer in the electron microscope. You can also look at the effects of changing the thickness of the surface film and of the energy of the electrons used to illuminate the surface. As the simulation runs, you can see the electrons bounce around inside the material, each dot represents the point at which x-rays characteristic of the film (cyan) or substrate (yellow) are created.

All materials will absorb x-rays, some more so than others depending on the energy of a particular x-ray. Selecting the Absorption Correction option will enable the simulation to include the effect of absorption on the number of x-rays reaching the spectrometer.

When the simulation ends, two histogram are drawn, showing how many x-rays are generated of each element as a function of depth.
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© Electric Park Research, 2006