Electron series resonance plasma discharges: Unmagnetized and magnetized.

摘要

This thesis explores high frequency electron series resonance in unmagnetized and magnetized bounded plasmas. Special interest is focused on low temperature plasmas in planar systems as such are useful for material processing and fusion devices.; Chapter 1, Chapter 2 and Chapter 3 describe simulation studies of unmagnetized electron series resonance (ESR) sustained discharges with comparisons to theory and experiment. These plasmas have many desirable characteristics. The input resistance is small and the drive voltage and current are in phase. The drive voltage is small (∼T_e) and the time average plasma potential is low (∼10T_e). A strong kinetic phase space bunching process is shown to provide electrons of sufficient energy for ionization, which allows discharge operation at low neutral pressure and low electron temperatures. At low pressure, the ion flux to the wall has a narrow angular spread about the normal and the ion bombarding energy distribution has a sharp peak at the plasma potential. Scaling laws at fixed pressure are shown to hold when RF frequency is varied smoothly (“chirping”) demonstrating continuous density control.; Research on magnetized electron series resonance (MESR) discharges is described in Chapter 4, Chapter 5 and Chapter 6. The resonant frequency is derived from cold plasma theory and shows two resonant modes. Simulations verify these modes to be the natural oscillatory frequencies of weakly magnetized plasmas in a planar plasma diode. A global model is established for magnetized resonant discharges. The interrelations among the plasma parameters and the drive terms are formulated for both resonant modes. The initiation of a MESR discharge and its steady state properties are discussed and compared to the unmagnetized case. Weak lock-on of MESR frequency to the drive frequency is observed in simulation. Similar V − I characteristics as those in ESR are found both in theory and in simulation. Different from the ESR discharges, MESR discharges show strong bulk heating. The scaling laws from the analytical model are also tested by simulation. The results show that we may control the plasma discharge parameters by the applied magnetic field: its magnitude and tilted angle; two more external controls than the ESR discharges.