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Rapid Formation of Distributed Plasm...

Xiang, Xun.

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Rapid Formation of Distributed Plasma Discharges using X-Band Microwaves.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Rapid Formation of Distributed Plasma Discharges using X-Band Microwaves./
Author:	Xiang, Xun.
Description:	143 p.
Notes:	Source: Dissertation Abstracts International, Volume: 77-10(E), Section: B.
Contained By:	Dissertation Abstracts International77-10B(E).
Subject:	Plasma physics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10119517
ISBN:	9781339807515

Rapid Formation of Distributed Plasma Discharges using X-Band Microwaves.
Xiang, Xun.

Rapid Formation of Distributed Plasma Discharges using X-Band Microwaves. - 143 p.

Source: Dissertation Abstracts International, Volume: 77-10(E), Section: B.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2016.

Observations of rapidly formed (<300 ns) distributed plasma discharges using high power X-band microwaves are presented. A cylindrical stainless steel chamber (15.2 cm long, 14.6 cm diameter) enclosed with polycarbonate windows (0.953 cm) was used to observe microwave breakdown in argon and neon gas mixtures from 50 to 250 torr. The chamber was illuminated by the output of a 16.2 kW, 800 ns pulse-width, 9.382 GHz magnetron with a 43 repetitive rate through an X-band waveguide pressed against the first polycarbonate window. Fast (50 ns) time-scale optical images of the plasma revealed the plasma formation and decay processes, as well as the plasma patterns for different plasma formation conditions. CST simulations were conducted to compare the electric field distribution inside the discharge chamber with the plasma patterns in the images. VUV (Vacuum Ultra-Violet) radiation was supported as the mechanism to enhance the plasma expansion and assist the formation of the plasma side lobes. Reflection Measurements showed 63% reflected power once plasma was formed, and a small amount of argon in neon shortened the breakdown time, verifying that the Penning effect lowers the breakdown threshold. Mixer measurements were taken, combined with a 1-D 6-region microwave plasma model to estimate the maximum effective plasma density as 2.2x1012 cm-3 with a corresponding maximum effective electron temperature of 2.5 eV in pure neon plasma at 100 torr under a Maxwellian distribution assumption. Optical emission spectroscopy (OES) assisted by the SPECAIR model determined the gas temperature in the microwave plasma as 350 +/- 50 K. OES line ratio measurements provided plasma parameters including time-evolved metastable and resonance densities, effective electron temperatures, electron densities for plasmas formed at 100 torr in pure neon and Ne/Ar (99:1) mixture gases. The comparison of time-evolved neon metastable and resonance densities in pure neon and Ne/Ar (99:1) mixture plasmas verified the Penning effect theory. Argon lines analysis showed that the effective electron temperature was likely to be a two-temperature combination. Neon lines analysis concluded the low-energy electrons had a maximum electron temperature of 2.3 eV at early times. Electron density estimates resulted in values comparable to 10 12 cm -3.

ISBN: 9781339807515Subjects--Topical Terms:

3175417
Plasma physics.

Rapid Formation of Distributed Plasma Discharges using X-Band Microwaves.
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245 1 0 $a Rapid Formation of Distributed Plasma Discharges using X-Band Microwaves.
300 $a 143 p.
500 $a Source: Dissertation Abstracts International, Volume: 77-10(E), Section: B.
500 $a Advisers: John E. Scharer; John Booske.
502 $a Thesis (Ph.D.)--The University of Wisconsin - Madison, 2016.
520 $a Observations of rapidly formed (<300 ns) distributed plasma discharges using high power X-band microwaves are presented. A cylindrical stainless steel chamber (15.2 cm long, 14.6 cm diameter) enclosed with polycarbonate windows (0.953 cm) was used to observe microwave breakdown in argon and neon gas mixtures from 50 to 250 torr. The chamber was illuminated by the output of a 16.2 kW, 800 ns pulse-width, 9.382 GHz magnetron with a 43 repetitive rate through an X-band waveguide pressed against the first polycarbonate window. Fast (50 ns) time-scale optical images of the plasma revealed the plasma formation and decay processes, as well as the plasma patterns for different plasma formation conditions. CST simulations were conducted to compare the electric field distribution inside the discharge chamber with the plasma patterns in the images. VUV (Vacuum Ultra-Violet) radiation was supported as the mechanism to enhance the plasma expansion and assist the formation of the plasma side lobes. Reflection Measurements showed 63% reflected power once plasma was formed, and a small amount of argon in neon shortened the breakdown time, verifying that the Penning effect lowers the breakdown threshold. Mixer measurements were taken, combined with a 1-D 6-region microwave plasma model to estimate the maximum effective plasma density as 2.2x1012 cm-3 with a corresponding maximum effective electron temperature of 2.5 eV in pure neon plasma at 100 torr under a Maxwellian distribution assumption. Optical emission spectroscopy (OES) assisted by the SPECAIR model determined the gas temperature in the microwave plasma as 350 +/- 50 K. OES line ratio measurements provided plasma parameters including time-evolved metastable and resonance densities, effective electron temperatures, electron densities for plasmas formed at 100 torr in pure neon and Ne/Ar (99:1) mixture gases. The comparison of time-evolved neon metastable and resonance densities in pure neon and Ne/Ar (99:1) mixture plasmas verified the Penning effect theory. Argon lines analysis showed that the effective electron temperature was likely to be a two-temperature combination. Neon lines analysis concluded the low-energy electrons had a maximum electron temperature of 2.3 eV at early times. Electron density estimates resulted in values comparable to 10 12 cm -3.
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