Absolute bremsstrahlung yields at 135° from53−keVelectrons on gold film targets

Abstract

Results are presented for the absolute bremsstrahlung yields at a backward angle of 135\ifmmode^\circ\else\textdegree\fi{} from $53\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ electrons on gold targets of thickness ranging from $66\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}28\phantom{\rule{0.2em}{0ex}}976\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{g}∕{\mathrm{cm}}^{2}$. The target thicknesses range from thin enough for single collision conditions to apply to thick enough for the yield to be dominated by multiple interactions. The results for all thicknesses are found to be in very good agreement with the predictions of PENELOPE, a Monte Carlo program which is based on ordinary bremsstrahlung and does not include any contribution from polarization bremsstrahlung. Absolute doubly differential cross sections are computed for the thinnest targets. The results are compared with two theoretical free atom cross section models, one for ordinary bremsstrahlung only and the second, the stripping approximation, for total bremsstrahlung including a contribution from polarization bremsstrahlung. The results agree with the predictions of ordinary bremsstrahlung for radiated photon energies from $5\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}53\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ and do not agree with the predictions of the stripping approximation. The conclusion, in contrast with recent free gas atom results, is that the absolute yields from solid films are well described by ordinary bremsstrahlung and do not require any additional polarizational bremsstrahlung contribution.