A model for low energy thick-target bremsstrahlung produced in an SEM

Abstract

A model for thick-target bremsstrahlung has been developed based on the approach used by Storm ( E. Storm, Phys. Rev. A.5, 2328 (1972).)and Ambrose et al. ( R. Ambrose, D. L. Kahler, H. E. Lehtihet and C. A. Quarles, Nucl. Inst. Meth. Phys. Res. B 56/57, 327 (1991).). The model integrates the thin-target cross sections ( Kissel, C. A. Quarles and R. H. Pratt, Atom. Data Nucl. Data Tables 28, 381 (1983).) over the target taking into account electron energy loss, electron back scattering and photon attenuation. The model is compared with measurements in reflection mode for atomic numbers from 4 to 79 and for electron energies between 5 and 25 keV. A JEOL JSM 6100 Scanning Electron Microscope is used for the electron beam, and a Link Si(Li) detector for the bremsstrahlung spectrum. Very good agreement is found between the model and the experimental results. Sensitivity of the model to various assumptions about electron back scattering and photon attenuation will be discussed. The model is also found to do as well as a recent empirical model ( Trincavelli, G. Castellano and J. A. Riveros, X-Ray Spectr. 27, 81 (1998).) in describing the photon energy dependence of the bremsstrahlung spectrum.