Acoustic Confinement and Characterization of a Microwave Plasma
- Author(s): Pree, Seth
- Advisor(s): Putterman, Seth J
- et al.
High amplitude acoustic fields are used to confine, characterize, and manipulate collisional plasmas with temperatures of a few thousand Kelvin. This dissertation describes the theory, experimental techniques, and apparatus necessary both to generate high amplitude sound in a few thousand Kelvin plasma and to use that sound field to manipulate the plasma within a resonant acoustic cavity. The acoustic field in a spherically symmetric oscillating plasma has been measured to have a Mach number of .03, which is sufficient to cause acoustic radiation pressure effects to confine the plasma to the center of its container. This field also generates convection in the conducting gas, which we study by measuring its effect on the acoustic spectrum, watching the convection occur on high speed video, and by measuring the microwave signal reflected off of the convecting plasma. I also discuss how the varying electrical conductivity due to a high amplitude acoustic field in a plasma may enable a new type of 3D thermoacoustic oscillation.