Presheath instability in two ion species multi-dipole weakly collisional plasma

Summary form only given, as follows. Ion-ion two stream instability was observed in the presheath of two ion species plasma. The noise was picked by an antenna close to the boundary of the plasma in an Argon-Helium plasma. The Helium was kept at a pressure of 1 mTorr and Argon was added at increments. The instability amplitude was found to increase closer to the presheath-sheath boundary. The amplitude depended on the concentration of the two species in the plasma. For 8% Argon by pressure, the amplitude reached a maximum. The frequency of the turbulence increased from 1.5 to 1.9 MHz as the distance from the boundary increased at the condition of maximum amplitude (by concentration).