For purpose of the electromagnetic pulse (EMP) protection research, a double-layer barrier of cylindrical plasma array was designed, and its protective performance to 6GHz high-power microwave (HPM) was conducted experimentally. Combining the distribution of the discharge plasma array, the shielding effectiveness of the double-layer plasma on 6GHz HPM pulse was studied. The main research contents and conclusions are as follows: The transmission energy of HPM decreased as the increase of plasma electron density, indicating an improved protection effect, with both double-layer and single-layer plasma array. Besides, the results showed that the transmission attenuation of HPM in double-layer structure was greater than that in single-layer structure because of the interlayer reflection. In addition, an interesting phenomenon was discovered during the experiment, which was that the boundary plasma units had a significant impact on the HPM transmission. The shielding effect of HPM was better with opening seven plasma units than that with opening whole plasma array. Finally, the spectral characteristics and transmission coefficients of the HPM were presented by Fourier transform, and the results of the protective performance were consistent with the above-mentioned time-domain analysis. The experiment results in this paper are of great significance in protecting against HPM based on plasma.
The transmission of High-Power Microwave (HPM) with a frequency of 1 GHz in a plasma double-line induced by intense femtosecond laser pulses is discussed by CST software. The influence of plasma electron density and collision frequency on HPM transmission performance is analyzed especially. The simulation results indicate that, the influence of plasma electron density on the transmission performance of HPM along the double-line is slight when the electron density is in the range of 1015 cm-3 ~1017 cm-3. It can also be obtained that the incident EM wave can propagate around the plasma double-line rather than in the over-dense plasma. We also discover that the attenuation value of the EM wave increases significantly with increasing the plasma collision frequency. Meanwhile, the attenuation value of the EM along the plasma transmission line can be calculated at approximately 0.94 dB/m and 1.56 dB/m when the plasma collision frequencies are 6×109 Hz and 1.5×1011 Hz, respectively. As can be seen, it is not necessary to increase the electron density of femtosecond laser plasma for achieving a high HPM transmission performance in the future applications.
Based on one-dimensional photonic crystals (1D PCs), we studied an innovative multispectral compatible stealth material for visible light, infrared, and 1.06-μm laser. The fabricated PCs had advantages of different colors, low emissivity in the atmospheric windows, and low reflectance at 1.06-μm waveband. According to some relevant experiments, the prepared films possessed colors of yellow, green, and blue, which could be used to simulate the color of the desert, woodland, and ocean, respectively. The infrared stealth performance of films showed that the thermal radiation in the atmospheric windows of 3 to 5 μm and 8 to 14 μm could be reduced effectively. In addition, the films’ reflectance spectra measured by spectrometer indicate that the reflectance at 1.06 μm is below 20%, which, in practice, could enormously reduce the echo power of incident lasers.
As a kind of special electromagnetic medium, femtosecond laser plasma has the potential of transmitting the electromagnetic wave. In this paper, a theoretical study on 6 GHz EM wave guiding performance of the plasma filament is carried out with the software XFDTD. Then, an experimental setup for the interaction between the EM wave and the plasma filaments is established. Based on the data measured by oscilloscope, the transmission properties of the EM wave along the filament are obtained. The results show the electric field is enhanced out of the waveguide with the plasma filament. The guiding performance of the plasma filament on the TE polarization wave is better than that on the TM one, which is consistent with the experimental results. For TE polarization wave, the plasma filament can reduce the transmission pulse energy greatly and the attenuation is up to 3.5 dB in the experiment. The research results show that the laser plasma filament can provide efficient transmission of the EM wave energy.
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