Title: Simulation of a non-equilibrium helium plasma bullet emerging into oxygen at high pressure (250–760 Torr) and interacting with a substrate

Abstract

A two-dimensional computational study of a plasma bullet emanating from a helium gas jet in oxygen ambient at high pressure (250–760 Torr) was performed, with emphasis on the bullet interaction with a substrate. Power was applied in the form of a trapezoidal +5 kV pulse lasting 150 ns. A neutral gas transport model was employed to predict the concentration distributions of helium and oxygen in the system. These were then used in a plasma dynamics model to investigate the characteristics of the plasma bullet during its propagation and interaction with a substrate. Upon ignition, the discharge first propagated as a surface wave along the inner wall of the containing tube, and then exited the tube with a well-defined ionization front (streamer or plasma bullet). The plasma bullet evolved from a hollow (donut-shaped) feature to one where the maximum of ionization was on axis. The bullet propagated in the gap between the tube exit and the substrate with an average speed of ~2 × 10⁵ m/s. Upon encountering a metal substrate, the bullet formed a conductive channel to the substrate. Upon encountering a dielectric substrate, the bullet turned into an ionization wave propagating radially along the substrate surface. For a conductivemore » substrate, the radial species fluxes to the surface peaked on the symmetry axis. For a dielectric substrate, a ring-shaped flux distribution was observed. The “footprint” of plasma-surface interaction increased either by decreasing the gap between tube exit and substrate, decreasing the relative permittivity of an insulating substrate, or decreasing pressure. As the system pressure was lowered from 760 to 250 Torr, the discharge was initiated earlier, and the plasma bullet propagation speed increased. A reverse electric field developed during the late stages of the ramp-down of the pulse, which accelerated electrons forming a brief backward discharge.« less

Authors:

Yan, Wen ^[1]; Economou, Demetre J. ^[2]

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+ Show Author Affiliations

1. Dalian Nationalities Univ., Dalian (China). School of Physics and Materials Engineering; Univ. of Houston, Houston, TX (United States). Plasma Processing Lab., Dept. of Chemical and Biomolecular Engineering
2. Univ. of Houston, Houston, TX (United States). Plasma Processing Lab., Dept. of Chemical and Biomolecular Engineering

Publication Date:

Tue Sep 27 00:00:00 EDT 2016

Research Org.:

Univ. of Houston, Houston, TX (United States). Plasma Processing Lab., Dept. of Chemical and Biomolecular Engineering

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES); National Natural Science Foundation of China (NSFC)

OSTI Identifier:

1468932

Alternate Identifier(s):

OSTI ID: 1326868

Grant/Contract Number:  

SC0001939

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 120; Journal Issue: 12; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY