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An Experimental Evaluation of the Atomic Number Effect

  • L. Parobek (a1) and J. D. Brown (a1)


A method for measuring the atomic number effect is developed using a sandwich sample technique. The depth distributions of x-ray production, ϕ(ρz) curves, have been measured for a zinc tracer in aluminum, copper, silver and gold matrices at 30, 25, 20 and 15 keV. The ϕ(ρz) curves were measured using a Cambridge Microscan 5 in which the electron beam is normal to the sample surface and the x-ray take-off angle is 75°.

Samples of the low concentrations of copper (∼1 Weight %) in aluminum, nickel, silver and gold were prepared. For each alloy system (for example, Cu - Al), three different concentrations of copper were prepared. The intensity ratios from the sample to the pure element (standard) for each system have been plotted against concentration. At such low concentrations of copper the relation between this ratio and concentration is linear. The slopes of the curves have been compared to the equivalent factors obtained as ratios of the area under F(ρz) curves for aluminum, silver and gold to the area under F(ρz) curve for copper, respectively. The F(ρz) curves are obtained from ϕ(ρz) curves; F(ρz) = ϕ(ρz) exp(-μρz csc ψ) where μ is mass absorption coefficient.

Comparisons are made between these experimental data and the current methods of calculating the atomic number effect.



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1. Castaing, R and Deseamps, J., J. Phys. Radium 16, 304 (1955).
2. Brown, J.D., Doctorate Thesis, University of Maryland (1966).
3. Poole, D.M., “Quantitative Electron Probe Microanalysis,” Heinrich, K.F.J., Editor, National Bureau of Standards Special Publikation 298, p. 93 (1968).
4. Duncumb, P and S.Reed, J.B., “Quantitative Electron Probe Microanalysis,” National Bureau of Standards Special Publication 293, p. 133 (1968).
5. Bishop, H.E., “Optique des Rayons X et Microanalyse,” Hermann, Paris (1967).
6. Wolf, R.C. and Macres, V.G., “Electron Probe Microanalysis,” Tousimis, A.J. and Marton, L., Editors, Academic Press, p. 73 (1969).


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