Nonlinear Fluid and Kinetic Effects in Nonneutral Plasmas

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This award supports a program of experiments, theory, and simulations on a range of fundamental nonlinear processes in plasmas. The studies will focus on problems for which precise experimental tests of theory can be obtained. Experiments will be performed on non-neutral plasmas, plasmas that contain a mixture of free electrons, ions, and uncharged species, using an electron trap and an ion trap with a broad range of operating regimes and diagnostics. The simplicity of these systems allows a depth of understanding and a precision of comparison between theory and experiment that is rarely possible otherwise. The award will support training of a graduate student, and results of the research will have broader applications to natural and engineered plasma systems, including space plasmas and fusion plasmas for power generation.The project is an integrated study of nonlinear plasma processes including wave-wave interactions; particle, heat, and momentum transport caused by applied electric and magnetic field perturbations; and effects associated with nonlinear particle trapping in both waves and applied fields. Ongoing experiments have observed nonlinear wave instabilities with features that are consistent with a new kinetic particle theory of nonlinear particle detrapping and retrapping in the wave troughs. These experiments, along with accompanying theory and simulations, will be extended in order to consider this trapped particle mechanism in the context of other waves, including nonneutral ion acoustic waves in mixed H-electron plasmas, and electron acoustic waves. New experiments on negative ion-electron nonneutral plasmas will also be pursued, making connections to nonlinear processes of importance in quasi-neutral plasmas and in plasmas used in anti-hydrogen production. A major focus will be on the interplay between effects of convective fluid nonlinearity versus kinetic trapped particle nonlinearity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.