The model of the influence of the electron refluxing on the electron transport and Kα emission

Abstract

AbstractIn our previous research (Zhao et al., 2016), we focus on the transport processes from hot electrons to Kα X-ray emission in a copper foil and nanobrush target when the electron refluxing effect is not taken into account. In this work, considering the refluxing effect, the transport of hot electrons in a solid target is studied by adding the electric fields both at the front and rear surfaces of the target with Monte Carlo code Geant4. Simulation results show that the electron refluxing has an important influence on Kα photon yield and the size of Kα radiation source. Kα yield from the 10-μm-thick target with the electron refluxing effect is 2.7–3.7 times more than that without the refluxing for the electron temperatures from 0.4 to 1.4 MeV. The laser-to-Kα photon energy conversion efficiency ${\rm \eta} _{L \to K_{\rm \alpha}} $ with the refluxing effect is always higher than that without the refluxing, and both of them decrease gradually with laser strength Iλ2. Considering the electron refluxing effect or not, the variations of Kα yield with the target thickness d are very different. A critical thickness of the target dc (~30 μm) is achieved to confirm whether the refluxing effect is valid for the target. For the target with the thickness d less than dc, the refluxing effect can enhance Kα yield with several times, while for the target with the thickness d larger than dc, the refluxing effect is not so effective. The full-width at half-maximum increases from 23 to 56 µm after including the refluxing effect by the electron beam with the radius of 10 µm and the temperature of 400 keV.