Ion velocity distribution function in intrinsic gas plasma under conditions when the main process is resonance recharging. Experiment

For the first time, the ion distribution function over energies and directions of the motion for $\rm He^+$ in $\rm He$ and $\rm Ar^+$ in $\rm Ar$ has been measured at the arbitrary value of the electric field by the method of the plane one-sided probe. The experiment is carried out under conditions when the ion velocity acquired at the mean free path is on the order of and larger than the average thermal velocity of atoms and resonance recharging is the dominating process in plasma. The obtained results make it possible to conclude that, in independent gas discharge plasma, even at moderate fields where $E/P = 10$–$20$ V/(cm Torr), the ion distribution function can have noticeable anisotropy and can strongly differ from the Maxwellian distribution.