Angular distribution of thick-target bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on Ag

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Experimental results are presented comparing the intensities of the bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on a thick Ag target, measured at forward angles in the range of 0\ifmmode^\circ\else\textdegree\fi{} to 55\ifmmode^\circ\else\textdegree\fi{}. When the data are corrected for attenuation due to photon absorption within the target, the results indicate that the detected radiation is distributed anisotropically only at photon energies $k$ that are approximately equal to the initial energy of the incident electrons ${E}_{0}$. The results of our experiments suggest that, as $k$/${E}_{0}$ \ensuremath{\rightarrow} 0, the detected radiation essentially becomes isotropic due primarily to the scattering of electrons within the target. A comparison to the theory of Kissel et al. [At. Data Nucl. Data Tables 28, 381 (1983)] suggests that the angular distribution of bremsstrahlung emitted by electrons incident on thick targets is similar to the angular distribution of bremsstrahlung emitted by electrons incident on free-atom targets only when $k$/${E}_{0}$ \ensuremath{\approx} 1. The experimental data also are in approximate agreement with the angular distribution predictions of the Monte Carlo program penelope.