Plasma Generation in a Non-Self-Sustaining Low-Pressure Discharge Supported by Electron Injection

The conditions of plasma generation in a low-pressure gas-discharge gap with injection of a flux of primary electrons is considered. It is shown that the formation of a potential hump, considered in the classical Langmuir model, with maximum above the anode potential, is not obligatory. At low ionization levels, plasma is formed due to ion capture in the potential well created by the injected electron flux, and its potential is lower than the cathode potential. At some intermediate ionization level the generated plasma can have a potential higher than the cathode potential, but lower than the anode potential. In this case, in the near-anode region of the gap, plasma is formed thanks to filling by ions of the potential well, and in the near-cathode region thanks to mutual compensation of the charges of the two particle fluxes: the primary electrons and the generated ions.