Emission of Characteristic L and K Radiation from Thick Tungsten Targets

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Abstract
A method is proposed for calculating L and Kphoton emission from thick tungsten targets bombarded by electrons accelerated by potentials of 12–300 kV. Electron energy losses, electron backscatter losses, and photon attenuation in the target are included. Agreement with measured K emission is obtained using the Arthurs‐Moiseiwitsch ionization cross sections and an expression of the form CZ (E 0 −k) 1− exp (−3k/E K ) (k/E 0 ) 1/3 1− exp (−E 0 /E K ) to describe the bremsstrahlung energy distribution. Satisfactory agreement with L‐emission measurements is obtained using the Mott‐Massey cross‐section formula with constants BLi =4 ELi , b L I =0.25×1.6, b L II =0.25×2.75, and b L III =0.25×4.2. Indirect radiation contributes 54–82% of the total K emission and 5–8% of the total L emission. The Webster‐Clark empirical relation Ii=Ci (U 0−1) n i agrees with calculation for U 0<3, with CK =5.1×1011 photon/sec mA sr, nK =1.67, CL =2.6×1011 photon/sec mA sr, and nL =1.5.

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