Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--Brigham Young University. Dept. of Chemistry and Biochemistry, 2004. / Includes bibliographical references.

Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 85-86). Also available in electronic format on the Internet.

published_or_final_version / Chemistry / Master / Master of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Inductively Coupled Plasma (ICP) facilities create high enthalpy ows to recreate atmospheric entry conditions. Although no condition has been duplicated exactly in a ground test facility, it is important to characterize the condition to understand how close a facility can come to doing so. An ICP facility was constructed at the University of Vermont for aerospace material testing in 2010. The current setup can operate using air, carbon dioxide, nitrogen, and argon to test samples in a chamber. In this work we investigate di erent ways to increase measured heat ux and expand our facility to operate supersonically. To do so, a water cooled injection system was designed to overcome failure points of the prior system. An investigation of heat ux methods that provide a baseline for the facility were also examined and tested. A nozzle con guration was also developed with an overall goal of increasing the plasma ow to reach sonic and supersonic velocities, allowing it to be compared with the existing subsonic system. An iterative approach was taken to develop a nozzle design that is robust enough to handle the harsh environment, yet adaptable to the pre-existing facility components. The current design uses interchangeable sonic and supersonic nozzles which also allow for appropriate plasma gas expansion. Data are taken through retractable and goose-neck probe sample holders during testing. Heat ux can be determined by use of a Gardon gage, slug calorimeter, and water cooled calorimeter. Total and static pressure are determined from a pitot tube and pressure tap, which are then manipulated into a velocity measurement. A comparison between subsonic and supersonic operation is then made with these data. Existing literature uses correlations between jet diameter and velocity gradients to determine the e ective heat ux. This investigation found that the experimental and theoretical heat ux results scale correctly according to the correlations.

No description available.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

The kinetic effects in an inductively coupled plasma (ICP) due to thermal motion of particles modified by self-consistent magnetic fields are studied by using a particle-in-cell (PIC) simulation. In the low pressure, low frequency regime, electron mean free paths are large relative to device size and the trajectories are strongly curved by the induced radio frequency (RF) magnetic field. This causes problems for linear theories, which ignore the influence of the magnetic field on the particles, and are therefore unable to recover effects accumulated along each nonlinear path.<p>The tools to perform high-performance parallel PIC simulations of inductively coupled plasmas were developed to allow rapid scanning of a broad range of the input parameters, such as wave amplitude, frequency, and plasma temperature. Different behavioural regimes are identified by observing the resultant variations in the skin depth, surface impedance, and ponderomotive force (PMF). At low electron-neutral collision rates, these are shown to include the local collisionless regime, the anomalous skin effect regime, and the nonlinear regime.<p>The local collisionless regime occurs at high driving frequencies and is characterized by plasma behaviour independent of both the driving frequency and amplitude: a short skin depth, low energy absorption, and strong PMF. The anomalous skin effect regime occurs at low frequencies and low amplitudes: the plasma varies with driving frequency, but not driving amplitude, the skin depth increases with frequency, the plasma is much more absorptive in the anomalous regime than in the local regime, and the PMF increases with frequency. The nonlinear regime occurs at low frequencies and high amplitudes: the plasma varies with driving amplitude, but not frequency, the skin depth decreases with amplitude, there is low energy absorption, and the PMF increases with wave amplitude.<p>The simulation runs in four modes: linear collisionless, linear collisional, nonlinear collisionless, and nonlinear collisional. The linear modes, in which the particles ignore the magnetic field, are used to validate the results against theory, while the nonlinear modes are used to test actual plasma behaviour. In linear collisionless mode, the plasma was found to exhibit only the local collisionless and anomalous skin effect regimes, as expected by theories. In nonlinear collisionless mode, the plasma exhibits the nonlinear regime in addition to the regimes found in linear mode. Finally, the nonlinear regime disappears in nonlinear collisionless mode because the curved paths caused by the magnetic field are disrupted by collisions.<p>Finally, the regime boundaries are investigated as a function of temperature. Since the plasma properties vary continuously, a boundary exists where two regimes share the same characteristics. From linear theories, it is known that the division between the local collisionless and anomalous skin effect regimes moves to higher frequencies as the plasma temperature is increased. When nonlinear fields are present, this still occurs, but in conjunction with the boundary between the local collisionless and nonlinear regimes moving to higher wave amplitudes. Temperature also effects the boundary between the anomalous skin effect and nonlinear regimes, causing the minimum frequency of the anomalous skin effect regime to be reduced at low wave amplitudes.

No description available.