Electromagnetic wave attenuation measurements in a ring-shaped inductively coupled air plasma

An aerocraft with the surface, inlet and radome covered large-area inductive coupled plasma (ICP) can attenuate its radar echo effectively. The shape, thickness, and electron density (Ne) distribution of ICP are critical to electromagnetic wave attenuation. In the paper, an air all-quartz ICP genera...

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Bibliographic Details
Published in:Journal of applied physics 2015-05, Vol.117 (20)
Main Authors: Xiaolong, Wei, Haojun, Xu, Jianhai, Li, Min, Lin, Chen, Su
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AIR
Air plasma
ANIONS
Applied physics
APPROXIMATIONS
ATTENUATION
COMPUTERIZED SIMULATION
DIFFUSION
Electromagnetic radiation
ELECTRON DENSITY
Electronegativity
GHZ RANGE
H-MODE PLASMA CONFINEMENT
Inductively coupled plasma
MAGNETIC FIELDS
MICROWAVE RADIATION
Negative ions
PLASMA
PLASMA DIAGNOSTICS
PLASMA SIMULATION
QUARTZ
Radar echoes
Radomes
Wave attenuation
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Summary:An aerocraft with the surface, inlet and radome covered large-area inductive coupled plasma (ICP) can attenuate its radar echo effectively. The shape, thickness, and electron density (Ne) distribution of ICP are critical to electromagnetic wave attenuation. In the paper, an air all-quartz ICP generator in size of 20 × 20 × 7 cm3 without magnetic confinement is designed. The discharge results show that the ICP is amorphous in E-mode and ring-shaped in H-mode. The structure of ICP stratifies into core region and edge halo in H-mode, and its width and thickness changes from power and pressure. Such phenomena are explained by the distribution of RF magnetic field, the diffusion of negative ions plasma and the variation of skin depth. In addition, the theoretical analysis shows that the Ne achieves nearly uniform within the electronegative core and sharply steepens in the edge. The Ne of core region is diagnosed by microwave interferometer under varied conditions (pressure in range of 10–50 Pa, power in 300–700 W). Furthermore, the electromagnetic wave attenuation measurements were carried out with the air ICP in the frequencies of 4–5 GHz. The results show that the interspaced ICP is still effective to wave attenuation, and the wave attenuation increases with the power and pressure. The measured attenuation is approximately in accordance with the calculation data of finite-different time-domain simulations.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4921533