Probe diagnostics of nuclear-excited plasma of uranium hexafluoride

The use of the probe diagnostics for determining the parameters of the plasma formed by nuclear fission fragments has been considered for reactor power levels of $100$–$1000$ kW. The current-voltage characteristics of plane and spherical probes have been measured in plasmas of helium and uranium hexafluoride at a pressure of several hundred torrs. The electron concentration is determined from a linear portion of the electron branch, whereas the concentration of positive ions is found from the saturation current according to the technique employing portions of the ion branch with large negative potentials of the probe. Kinetic models of the helium and uranium hexafluoride plasmas have been proposed, and a numerical analysis of the ionic composition of the plasma has been performed. The electron concentration in the helium plasma is determined by the ionization rate and the rate of dissociative recombination with helium ions. The electron concentration in the uranium hexafluoride plasma is determined by the ionization rate and the rate of electron attachment to uranium hexafluoride molecules. The experimental and calculated concentrations of ions and electrons are in satisfactory agreement.