Impact Energy and Angular Dependence of L X-ray Emission from a Thick Polycrystalline Tungsten Element Induced by 15-25 keV Electrons

The impact energy and angular dependence of L X-rays of a thick polycrystalline tungsten (W; atomic number, Z = 74) target induced by 15-25 keV electrons has been measured at different angles varying from 15 degrees to 75 degrees at intervals of 5 degrees using a Si PIN photodiode detector. The variation of measured relative intensity of L-l, L-alpha, L-beta and L-gamma characteristic lines as a function of incidence angle is found to be anisotropic and the measured variation compares well with the PENELOPE simulation results. The angular variation of intensity ratio of L-l/L-alpha and L-beta/L-alpha shows anisotropic distribution, whereas the angular variation of the L-gamma/L-alpha ratio exhibits almost isotropic distribution within the uncertainty of measurements. These measured ratios are found to be in good agreement with Monte Carlo (MC) calculations. The measured intensity ratios of L-beta/L-alpha and L-gamma/L-alpha at a given incidence angle show a linear dependence with impact energy and exhibit good agreement with simulation results; however, the measured intensity ratio of L-l/L-alpha shows a non-linear variation with the impact energy and yields poor agreement with theoretical calculations.