Bulletin of the American Physical Society
71st Annual Gaseous Electronics Conference
Volume 63, Number 10
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session KW2: Glows: Dc, Pulsed, Microwave, other |
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Chair: David Staack, Texas A&M University Room: Oregon Convention Center A105 |
Wednesday, November 7, 2018 2:00PM - 2:15PM |
KW2.00001: Locally-enhanced generation of plasma by magnetic resonance of double-split-ring resonators Akinori Iwai, Yoshihiro Nakamura, Yuki Kabe, Osamu Sakai We performed experiments of plasma discharge with a set of double-split-ring resonators (DSRRs) in the rectangular waveguide for 2.45-GHz waves, where their magnetic resonance takes place around the microwave frequency. When high-power waves enter plasmas, inherent nonlinearity of plasma clearly emerges. Electron density directly affects the intensity of a nonlinear current. Our group has studied low-pressure plasma excited by microwaves combined with DSRRs, and proposed a scheme of efficient penetration of high-power microwaves into overdense plasmas by negative-refractive index because DSRRs show negative permeability based on the magnetic resonance. We experimentally observed strongly-enhanced second-harmonic waves with DSRRs [1] and explained this nonlinearity is induced the local connection between plasma and DSRRs [2]. In this report, we show a further expanded phenomenon based on the magnetic resonance associated with this nonlinearity, i.e., the non-uniform generation of plasma around DSRRs and clarify this non-uniform profile, with locally-enhanced electron energy and density, is caused by the resonance. [1] A. Iwai, Y. Nakamura and O. Sakai, Phys. Rev. E, 92 (2015) 033105. [2] A. Iwai, Y. Nakamura, A. Bambina, and O. Sakai, Appl. Phys. Express, 8 (2015) 056201. [Preview Abstract] |
Wednesday, November 7, 2018 2:15PM - 2:45PM |
KW2.00002: Plasma-fluid and plasma-surface interactions of nanosecond pulsed plasmas Invited Speaker: David Pai Interactions with fluids and surfaces are key avenues for improving the effectiveness of nanosecond pulsed plasmas for atmospheric-pressure applications in materials science, among other areas. To investigate such interactions, we combine space- and time-resolved optical diagnostics: emission microspectroscopy of plasmas, in-situ Raman microspectroscopy of surfaces, and particle image velocimetry of fluid flow. The first part of the talk will concern nanosecond repetitively pulsed (NRP) microplasmas generated in air at atmospheric pressure, which achieve arc-like levels of ionization while maintaining a strong degree of non-equilibrium. In the presence of a metal substrate biased to high dc voltage, the microplasma generates an electrohydrodynamic (EHD) flow between itself and the substrate. Ions generated by the microplasma create an immediate acceleration of the fluid, followed by the development of plume-like convective flow. The relative importance of the thermal versus EHD character of the plume is adjustable in a straightforward fashion. The second part of the talk will cover NRP discharges in atmospheric air generated using a surface discharge geometry. We will focus on how the presence of the plasma affects the properties of various propagating surfaces such as dielectric films and semiconductors, with an emphasis on transient changes during plasma-surface interaction. [Preview Abstract] |
Wednesday, November 7, 2018 2:45PM - 3:00PM |
KW2.00003: Abstract Withdrawn
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Wednesday, November 7, 2018 3:00PM - 3:15PM |
KW2.00004: A novel linear microwave plasma source using circular TE$_{\mathrm{11}}$ mode and comparison with co-axial TEM mode Ju-Hong Cha, Ho-Jun Lee For conventional linear microwave plasma sources with co-axial TEM waveguide, the wave electric field is directed perpendicular to the quartz window surface. There is a relatively large resistive loss on the window, and the electron loss increases due to the field direction. To improve performances of linear microwave plasma sources, a novel linear microwave plasma source suitable for deposition and etching processes has been developed. In the proposed plasma source, circular TE$_{\mathrm{11}}$ mode was used for plasma generation. After mode conversion from rectangular TE$_{\mathrm{10}}$ to circular TE$_{\mathrm{11}}$, 2.45 GHz microwave power is transferred to the plasma through the continuous line slot antenna along the wave propagation direction. The direction of radiated electric field was made to be almost parallel to the quartz window to reduce the electron loss. Properties of the plasma source are investigated by fluid simulation and home-made single Langmuir probe, which confirmed that proposed source has better plasma generation efficiency compared with the conventional source. For 300mTorr Ar plasma with 0.6kW microwave power, plasma density improvement about 200{\%} was achieved. In addition, it was observed that the position of the maximum electron density is shifted away from the window surface. [Preview Abstract] |
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