Date of Award
Master of Science (MS)
Electrical & Computer Engineering
Shirshak K. Dhali
While generating a plasma under laboratory conditions, any attempt to scale the pressure and volume leads to instabilities due to the build-up of localized space-charge. This poses a challenge in the design of the discharge chamber, type of excitation field, and the type of gas that is used in the discharge. This work investigates a spatially and temporally varying electric field to control the formation of space-charge in large-volume (greater than 5 mm in the smallest dimension) near atmospheric pressure. The simulations show that in a space-charge dominated transport, the charged species disperse both in azimuthal and radial directions in cylindrical geometries. This leads to stable discharges due to better control over the space charge. In this approach, multiple conformal electrodes along the length of the cylindrical discharge chamber are excited with phase-shifted sinusoidal voltage. This causes a rotating electric field, which disperses the space-charge to prevent instabilities from developing. The phase-shifted waveforms are obtained by programming an FPGA. The digital waveform generated by the FPGA is then converted to an analog signal and is amplified to a voltage above a kV. The phase staggered high voltage is applied to a custom chamber with eight electrodes. The chamber was constructed with 3-D printing to accommodate the subtle feature required for a miniature discharge chamber. This thesis describes the design and implementation of a novel discharge chamber and the associated power system.
"Hardware Development for the Generation of Large-Volume High Pressure Plasma By Spatiotemporal Control of Space Charge"
(2020). Master of Science (MS), Thesis, Electrical/Computer Engineering, Old Dominion University, DOI: 10.25777/ns6y-5v12