X‐ray production in thin films by electrons with energies between 40 and 100 keV. 1—Bremsstrahlung cross‐sections

Abstract

Abstract Cross‐sections for bremsstrahlung production in thin films may be derived theoretically only if certain approximations are made or if there is recourse to numerical techniques. In this paper, two approximate equations, one based on the Sommerfeld theory and the other on the Bethe–Heitler theory, are assessed for their accuracy in predicting cross‐sections differential in photon energy and emergence angle when a thin foil target is bombarded with electrons with energies between 40 and 100 keV. Experimental data are presented from eight different target materials and these are processed initially to make comparisons between experimental and theoretical spectral shapes and subsequently to compare observed and predicted absolute cross‐section values. Except for the heaviest target material (Au), the Bethe–Heitler theory provided a satisfactory description of all experimental observations. In contrast, the Sommerfeld theory provided a significantly inferior description of spectral shapes and consistently overestimated absolute cross‐sections by 15–20%.