Statistical analysis of high power microwave surface flashover delay times in nitrogen with metallic field enhancements

Journal Article · Tue Nov 15 00:00:00 EST 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3662108· OSTI ID:22047093

Foster, Jonathan; Krompholz, Hermann; Neuber, Andreas ^[1]

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1. Center for Pulsed Power and Power Electronics, Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409-3102 (United States)

The physical mechanisms that contribute to atmospheric breakdown induced by high power microwaves (HPMs) are of particular interest for the further development of high power microwave systems and related technologies. For a system in which HPM is produced in a vacuum environment for the purpose of radiating into atmosphere, it is necessary to separate the atmospheric environment from the vacuum environment with a dielectric interface. Breakdown across this interface on the atmospheric side and plasma development to densities prohibiting further microwave propagation are of special interest. In this paper, the delay time between microwave application and plasma emergence is investigated. Various external parameters, such as UV illumination or the presence of small metallic points on the surface, provide sources for electron field emission and influence the delay time which yields crucial information on the breakdown mechanisms involved. Due to the inherent statistical appearance of initial electrons and the statistics of the charge carrier amplification mechanisms, the flashover delay times deviate by as much as {+-}50% from the average, for the investigated case of discharges in N{sub 2} at pressures of 60-140 Torr and a microwave frequency of 2.85 GHz with 3 {mu}s pulse duration, 50 ns pulse risetime, and MW/cm{sup 2} power densities. The statistical model described in this paper demonstrates how delay times for HPM surface flashover events can be effectively predicted for various conditions given sufficient knowledge about ionization rate coefficients as well as the production rate for breakdown initiating electrons.

• OSTI ID: 22047093
• Journal Information: Physics of Plasmas, Vol. 18, Issue 11; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHARGE CARRIERS
CHARGED-PARTICLE TRANSPORT
ELECTRONS
FIELD EMISSION
FLASHOVER
GHZ RANGE
HIGH-FREQUENCY DISCHARGES
INTERFACES
IONIZATION
MICROWAVE RADIATION
NITROGEN
PLASMA
PLASMA DENSITY
PLASMA PRESSURE
PULSES
TIME DELAY