Continuous plasma coherent emission is maintained by repetitive Langmuir collapse driven by the nonlinear evolution of a strong electron two-stream instability. The Langmuir waves are modulated by solitary waves in the linear stage and electrostatic whistler waves in the nonlinear stage. Modulational instability leads to Langmuir collapse and electron heating that fills in cavitons. The high pr...

Density filamentation has been observed in many beam-plasma simulations and experiments. Because current is a pure transverse mode, charge density cannot be produced directly by the process. To explain this phenomenon, several mechanisms are proposed such as coupling of Weibel instability to two-stream instability, Langmuir wave, differences thermal velocities between beam return currents, magn...

Title of Document: STUDY OF THE FEMTOSECOND DYNAMICS AND SPECTROSCOPY OF LASER IONIZED PLASMAS. JJennifer Anne Elle, Doctor of Philosophy, 2015 Directed By: Professor Howard Milchberg Department of Physics Ultra-short laser pulses are used to ionize gas in different configurations and study the plasma and ionization dynamics. The variation in non-linear index of refraction as a function of time...

It is well known that additional low-frequency waves arise when a second ion population is added to a plasma normally consisting of protons and electrons. Here, we investigate stationary structures streaming with a sub-fast speed in such a bi-ion plasma. It is shown that in addition to the usual “solitons”, which have already been described for a single-ion plasma, a new type of stationary stru...

Many kinetic plasma instabilities, in quite di erent physical systems, share a genuinely similar mathematical structure near isolated phase-space islands. For this reason, dynamical features such as faster-than-exponential growth of the instability, as well as nonlinear frequency sweeping, are found to be universal. Numerical f methods, which follow the evolution of the (nonlinear) perturbed di...

Plasma-wakefield excitation by positron beams is examined in a regime for which the plasma dynamics are highly nonlinear. Three dimensional particle-in-cell simulations and physical models are presented. In the nonlinear wake regime known as the blowout regime for electrons, positron wakes exhibit an analogous "suck-in" behavior. Although analogous, the two wakefield cases are quite different i...

Influence of formation of surface nano/ultrafine structure using deep rolling on plasma nitriding and tribological properties of the AISI 316L stainless steel was investigated. Initially, the deep rolling process was carried out on the bar-shaped specimens at 15 cycles with 0.2 mm/s longitudinal rate and 22.4 rpm bar rotation. Then, plasma nitriding treatment was applied on the as-received...

Title of Dissertation: HIGH POWER NONLINEAR PROPAGATION OF LASER PULSES IN TENUOUS GASES AND PLASMA CHANNELS Jianzhou Wu, Doctor of Philosophy, 2005 Dissertation Directed By: Professor Thomas M. Antonsen, Jr. Department of Physics The nonlinear propagation over long distances of moderate intensity laser pulses in tenuous gases is studied. The dynamics of these pulses will be affected by nonline...