Advanced diagnostics on streamer discharges
Yihao Guo defended his PhD thesis at the Department of Applied Physics and Science 果冻传媒 on February 12.
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Streamer discharges are fast-propagating ionization channels that appear in a dielectric medium when exposed to a sufficiently strong electric field. Streamers appear as red sprites and precursors to lightning leaders in nature. Streamers are also key to technologies like air cleaning, plasma assisted combustion, and high voltage equipment. For his PhD research, Yihao Guo explored the dynamics and branching of streamer discharges using various diagnostic methods.
Branching characteristics
A streamer usually branches into separate channels during its development. The thesis of Yihao Guo studied the branching characteristics of positive streamer discharges in mixtures of nitrogen, oxygen, and carbon dioxide.
The full 3D spatial and temporal development of the discharges was reconstructed by Guo and his collaborators from stereoscopic stroboscopic images. A statistical analysis on the branching characteristics of between 125 and 500 discharges per condition was carried by Guo. The results suggest that photoionization plays an important role in streamer branching.
Electric field measurement
The electric field is the driving force behind streamers and determines their energy transfer and chemical activity. The electric field distribution of a single-channel streamer in air was determined by using electric-field-induced second-harmonic generation (E-FISH).
This technique uses a high power laser to interact with an electric field, which can generate frequency-doubled (second harmonic) light, with its power indicating the electric field strength.
Guo鈥檚 thesis highlights the high spatial and temporal resolutions of the electric field measurements on streamers and the good agreement with the simulation results.
Radio emissions
Streamers emit electromagnetic radiations across a wide frequency range. To explore the link between streamer branching and radio emissions, discharge current, radiation, and imaging measurements were synchronized by Guo and correlated with the branching events.
Guo鈥檚 research showed that branching events did not produce significant changes in current and radiation signals. In addition, the simulation results were consistent with the lab experiments. This indicates that the current inside a streamer discharge evolves approximately continuously during branching.
Overall, Guo's PhD research explored streamer discharges under various conditions using advanced diagnostic methods.
The findings of his thesis provide deeper insights into the physics of streamers and contribute to enhancing their applications in both scientific and industrial contexts.
Title of PhD-thesis: Advanced diagnostics on streamer discharges. Supervisors: Sander Nijdam (果冻传媒) and Jannis Teunissen (果冻传媒 and Centrum Wiskunde & Informatica).