Seed electron production from O{sup -} ions under high-power microwave excitation
- Center for Pulsed Power and Power Electronics, Departments of Electrical and Computer Engineering and Physics, Texas Tech University, MS 43102, Lubbock, Texas 79409 (United States)
Surface and volume breakdown formation during pulsed high-power microwave (HPM) excitation can severely limit the power densities which can be transmitted into an atmospheric medium. Recent studies in this area have focused on developing models which accurately predict flashover formation at either dielectric/air interfaces or in the gas volume directly adjacent to these interfaces. These models are typically validated through comparison with experimentally gathered data. With respect to HPM surface flashover, experiments in the S-band at 5 MW power levels have reported on the contributing factors to flashover development including the effects of gas type, pressure, and relative humidity. A Monte Carlo-type electron motion simulation code, MC, has been developed to calculate the increasing electron density during flashover formation in this case. Results from the MC code have exhibited a quantitative agreement with experimental data over a wide range of atmospheric conditions. A critical parameter to flashover development is the stochastic process involving the appearance of initiatory or ''seed'' electrons, as seen by the reduction in flashover delay time by approximately 10-20% in the presence of external ultraviolet illumination. While the current version of the MC code seeds the flashover location with electron densities on the order of background ion densities produced by cosmic radiation, it fails to incorporate the field-assisted collisional detachment processes which are often assumed to be the primary origin of these electrons on the time scales of interest. Investigation of these processes and development of more accurate seeding in the MC code is a key step toward predicting HPM flashover over a wide range of parameters, particularly in the presence of highly electronegative gases such as SF{sub 6} or O{sub 2}, in which there is an absence of free electrons with zero applied field.
- OSTI ID:
- 21133986
- Journal Information:
- Journal of Applied Physics, Vol. 103, Issue 6; Other Information: DOI: 10.1063/1.2841504; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
AIR
COSMIC RADIATION
DIELECTRIC MATERIALS
ELECTRON DENSITY
ELECTRONS
EXCITATION
FLASHOVER
HIGH-FREQUENCY DISCHARGES
HUMIDITY
ION DENSITY
MICROWAVE RADIATION
MONTE CARLO METHOD
OXYGEN
PLASMA DENSITY
PLASMA SIMULATION
POWER DENSITY
STOCHASTIC PROCESSES
SULFUR FLUORIDES
TIME DELAY
ULTRAVIOLET RADIATION