WAKE-FIELD EXCITATION IN 2-COMPONENT AND 3-COMPONENT PLASMAS

Experiments on plasma wake fields are presented. Properties of wake fields in a two-component plasma are briefly reviewed and compared with the experiments of Nishida et al. [Phys. Rev. Lett. 66, 2328 (1991)]. Characteristics of wake fields in a three-component plasma that consists of positive ions, negative ions, and electrons are then described. These wake fields are created following the injection of either positive or negative ions into a plasma. The relationship between ion-acoustic fast modes and the wake field are investigated and the excitation mechanism is discussed. Critical negative-ion concentrations and modulation effects are examined. The excitation of the wake fields is interpreted using a fluid model.