Measurement of the angular distribution of thick target bremsstrahlung produced by 10-25 keV electrons incident on Ti and Cu targets

Angular distributions of bremsstrahlung photons produced by 10-25 keV electrons incident on thick Ti (Z = 22) and Cu (Z = 29) targets using a Si-PIN photodiode detector have been measured and new results are reported. The incidence angle, defined as the angle between the direction of the incident electrons and the normal of the target surface, varied between 15° and 75°. The intensity of the bremsstrahlung radiation, differential in angle and energy, that is, the double differential bremsstrahlung yield, was obtained by varying the incidence angle, while the photon detector was kept fixed perpendicular to the electron beam direction in reflection geometry. The experimental bremsstrahlung yields were normalized so that the values measured at 45° coincide with the results of Monte Carlo simulations. For the other incidence angles, the measured yields are found to be in good agreement with simulation results, within the experimental uncertainties. Our results suggest that the bremsstrahlung radiation emerging from the considered electron-target collision reactions is anisotropic in general; a relatively larger anisotropy is observed for all energy photons produced by high-energy electrons compared to that by low energy electrons. Furthermore, there is an indication of a weak dependence of the angular variation of the bremsstrahlung yield on atomic number (Z) of the bombarded targets.