Instabilities in dusty negative ion plasmas

Summary form only given. Recently there has been interest in the properties of dusty negative ion plasmas, including dust charging and collective behavior. Electronegative dusty plasmas are of interest from the perspective of both basic physics and applications. Because the addition of negative ions to a dusty plasma can change the dust charge state, and add new sources of free energy such as ion currents, such plasmas could provide useful tools with which to study the physics of dust wave instabilities. Moreover, electronegative dusty plasmas can occur in industrial processing plasma devices, where the control of dust is an issue. Here, the behavior of the dust acoustic instability in a collisional, dusty negative ion plasma is considered using kinetic theory, for parameters that may be representative of possible laboratory dusty plasmas. First, the case of an unmagnetized plasma is considered, where the dust is negatively charged and the ion drift speeds are comparable to their thermal speeds. It is found that as the negative ion concentration epsiv increases, the direction of propagation of the unstable waves reverses; for large enough epsiv the instability is quenched. In addition, at certain negative ion concentrations, unstable waves can propagate in opposite directions (due to dissipative instability at long wavelengths, and kinetic instability at short wavelengths). Next, the analysis is extended to consider the effects of an external magnetic field, for parameters such that the ions and electrons are magnetized, but the charged dust grains are unmagnetized.