Ion Acceleration by Beating Electrostatic Waves: Theory, Experiments and Relevance to Spacecraft Propulsion

A recently discovered ion acceleration mechanism, which appears to oc-cur naturally in Earth's ionosphere, holds promise as an effective means to energize ions for applications in thermonuclear fusion and space plasma pro-pulsion. Unlike previously known mechanisms for energizing plasmas with electrostatic (ES) waves, and which accelerate only ions whose initial veloci-ties are above a certain threshold (close to the wave's phase velocity), the new acceleration mechanism involving pairs of beating ES waves is non-resonant and can accelerate ions with arbitrarily small initial velocities. This offers a more effective way to couple energy to plasmas. I will discuss the fundamen-tals of the nonlinear dynamics of a single magnetized ion interacting with a pair of beating ES waves and show that there exists necessary and sufficient conditions for the phenomenon to occur. I will then present recent results from a dedicated experiment in my lab in which laser-induced fluorescence (LIF) measurements of ion energies have provided the first laboratory observa-tion of this acceleration mechanism. The talk will conclude with a few ideas on how the fundamental insight can be applied to develop novel plasma pro-pulsion concepts.
Dr. Edgar Choueiri is Professor of Mechanical & Aerospace Engineering and Director of the Program in Engr. Physics and of the Electric Propulsion & Plasma Dynamics Lab. at Princeton University where he also received his PhD in Aerospace Engineering/Plasma Science. Prof. Choueiri has published more than 140 journal articles and conference papers on plasma thrusters, plasma and space physics, instabilities and turbulence in collisional plasmas, plasma accelerator modeling, and applied math. Prof. Choueiri has given 55 invited seminars. He served as Chair of the American Institute of Aeronautics and Astronautics' Electric Propulsion Technical Committee for which he received AIAA's distinguished service award. He was one of the twelve founding members of the Lebanese Academy of Sciences (ASL) and in June of 2008, he was elected President of ASL.