Modeling x-ray emission in a high voltage vacuum gap including secondary electron emission

Summary form only given. In a high voltage vacuum electron device, two key factors influence the behavior of the high voltage gap: x-ray photons and secondary electrons generated by impact of primary beam electrons at collector surfaces. When the electrons hit the surfaces such as collector, drift tube, and anode, x-ray photons and secondary electrons are created. The created x-ray photons interact with the surfaces, inducing electron emission by the Einstein photoelectric effect. The secondary electrons, which are created by the electron impact, impact nearby surfaces, resulting in generation of x-ray photons and secondary electrons. The electrons created by these mechanisms can change the behavior of gap with the change of current, as well as ionizing any residual background gas. One of the issues here is that the ratio of this photoelectric current due to primary beam x-rays to primary beam current is of the magnitude of ~10^-4; i.e. insufficient to account for the deficit in the gap current (Latham, 2006). The secondary electrons play an important role in generating additional electrons, because the secondary electrons generate soft x-rays (less than 0.5 keV) upon impact with the anode or collector surfaces. The yield of photoelectrons per incident photon is 10^-6 for photon energies greater than 10 kV and -0.1 for photon energies less than 0.5 kV. Our model includes the generation of x-rays by the primary and secondary currents, as well as the photo-emission of the secondary electrons. We investigate the relationship between secondary electron emission and x-ray emission quantitatively.