Effect of a high-frequency field on the reflection of ion acoustic waves from the sheath at a grid

Experiments are described which show that the reflection coefficient for ion acoustic waves (IAW) from the sheath at a grid is affected by an HF electric field with a frequency f/sub HF/f/sub pi/, the energy distribution of the ions passing through the grid develops a hot tail and the reflected wave suffers enhanced Landau damping. If Phi /sub 0/>or approximately=k/sub B/T/sub e//e and f/sub HF/>