High-frequency electron resonances and surface waves in unmagnetized bounded plasmas.

摘要

As all laboratory and industrial plasma devices have boundaries, understanding the plasma-wall interaction is critical. This thesis explores high frequency (beyond the ion plasma frequency) resonances and surface waves in unmagnetized bounded plasmas. Special emphasis is placed on low-temperature plasmas in planar systems as such are useful for materials processing.; Chapter 1, Chapter 2 and Chapter 3 conduct simulation studies of electron series resonance sustained discharges with comparisons to theory and experiment. These plasmas have many desirable characteristics (resistive V-I phase, frequency tunable density, low-temperature, low-pressure).; Surface wave plasmas are the natural extension to resonant plasmas and are promising for use in large-area plasma sources. Appropriate for large-area device modeling, an electromagnetic theory of surface wave propagation in a warm non-uniform plasma is developed and compared to previous theoretical work (Chapter 4 and Chapter 5). In Chapter 6, several PIC simulations are conducted to validate the electromagnetic theory. In Chapter 7, numerical techniques suitable for computing the wave dispersion and impedance in a large-area low-temperature plasma are developed.; Utilizing much of the research conducted here, Chapter 8 demonstrates a novel application of surface waves. Through a resonant wave-particle interaction (“Landau resonant heating”), the electron velocity distribution function is controllably modified by a standing surface wave excited with a distributed periodic electrode. Simulation results indicate this Landau resonant heating can be used to dramatically enhance important reactions in low-temperature low-pressure plasmas including electron-impact excitation and electron-impact ionization.; In conducting this research, an algorithm to effectively eliminate cache thrashing in a particle-in-cell simulation was developed, resulting in a 40 to 70 percent performance gain on typical workstations. The algorithm is described in Chapter 9. Also several implicit methods for solving the Maxwell equations were developed with superior noise and stability properties compared to the standard explicit leap-frog finite-difference-time-domain algorithm (Chapter 10).