Two-Stream Instability with a Growth Rate Insensitive to Collisions in a Dissipative Plasma Jet*

The electron-ion two-stream instability (Buneman instability) is conventionally considered as a collisionless instability with the presumption that collisions inhibit this instability. We propose here a collisional two-fluid model which involves a low-frequency two-stream instability that is indifferent to collisions. This model likely explains previously observed localized dimming of visible light and a simultaneous, localized burst of EUV radiation from a collisional, current-carrying laboratory plasma jet the cross-section of which is constricted by a kink-instigated Rayleigh-Taylor instability. Despite the collision frequency greatly exceeding the growth rate of the instability, the instability can still cause an exponential growth of electron velocity and a rapid depletion of particle density. Nevertheless, high collisionality has an important effect as it enables the development of a double layer when the cross section of the plasma jet is constricted. Numerical solution of the model shows good agreement with experimental observations.