| "Inertial Confinement Fusion" (ICF) is one of the ways to realize the controlled thermonuclear fusion, and it plays a significant role in all fields from scientific research, industrial applications to solving the energy crisis. The materials generated by implosion move to the heart of the target to release thermonuclear plasma's energy, Inertial Confinement Fusion derived by laser use the laser, or the X-ray source generated by interaction of laser and material as the driver, compressed the main fuel (Deuterium-Tritium) to high-density and high-temperature to achieve the ignition conditions. Prior to the dispersion, the nuclear fuel has a full thermonuclear burning, releasing a large number of fusion energy.Rayleigh - Taylor Instability occurred between the layers of different densities, if the acceleration from the light material to the weight material, when a small disturbance occurred the in the interface, which usually is a small perturbation of the planar uniformity of the laser , or the surface roughness of the target, Rayleigh - Taylor Instability will be developed. In time it occurred mainly in the accelerated phase and deceleration phase of Inertial Confinement Fusion. In space, it occurred between the layers of different densities. To the spherical target of Deuterium-Tritium as an example, Rayleigh - Taylor Instability mainly occurred between the ablation layer and the Deuterium-Tritium ice layer, the Deuterium-Tritium ice layer and Deuterium-Tritium gas layer. With the development of Rayleigh - Taylor Instability, it will enlarge the roughness of target's surface, with the result that the uniform compression of the spherical target has been damaged by Rayleigh - Taylor Instability, would seriously have affected the final ignition of Inertial Confinement Fusion, so the research of Rayleigh - Taylor Instability has become a key issue of Inertial Confinement Fusion. In addition, for the experimental research of Rayleigh - Taylor Instability, if you want to find the physical laws of Rayleigh - Taylor Instability, the data-processing of the experimental image would be needed, on the other hand, the data-processing is able to give a meaningful feedback to the physical experiment on Rayleigh -Taylor Instability. In this paper, focusing on laser-driven Inertial Confinement Fusion, we discussed on the principles and mechanisms of 7 - Taylor Instability, carried out the corresponding physical experimental study, and completed the data processing and analysis of experimental image. As follows:1: On the high-power laser devices of ShenGuang II, we got the static and dynamic experimental images of the Rayleigh - Taylor Instability. First, we obtained a clear static image of Al target(the amplitude of 18 micron, the period of 50 micron, sine wave modulation); Second, through the pinhole, we obtained the dynamic images of Al target(0.6～0.8 micron-amplitude, 49.5 micro- period, sinusoidal modulation), measured by the Face-on way; Third, through the point projection, we obtained the dynamic images of CH target(2.2～2.75 micron-amplitude, 75micro-period, sinusoidal modulation), measured by the Side-on way.2: Under the optical arrangement of point projection, we got the Modulation Transfer Function (MTF) of the imaging system. According to the knife-edge image, we obtain the Edge Spread Function (ETF), then with the principle of differential, the Line Spread Function (LSF) curve would be got, for Discrete Fourier Transform (DFT) of the LSF curve, we could obtain the MTF curve with frequency of knife-edge experimental image, which do a favor to complete the experimental data-amendment of the imaging system.3: For the experimental image of R-T hydrodynamic instability obtained with the X-Ray probe passing through the modulated target, the FFT method was applied to smooth it first (removing the high-frequency noise), after considering the non-uniformity of the backlighting, the X-Ray intense distribution permeating the target can be presented. With the physical model of the R-T hydrodynamic instability, the temporal evolvement of the R-T instability's increasing factor can be given finally, in order to lay the foundation of dealing with the dynamic experimental data.4: Some of the laws over time of the Rayleigh - Taylor Instability have been got by completing data processing of the experimental dynamic image. For the experimental images measured under the Face-on Optical arrangement, the experimental data was smoothed by the FFT method to remove the high-frequency noise after considering the non-uniformity of the backlight. After discounting the effect of by self-luminous of Al, the intensity distribution can then be extracted. With the physical model of the R-T growth for the backlit contrast (the peak-to-valley modulation), the temporal evolvement of the RT growth factor and the optical depth was obtained finally from the 4.75keV X-Ray Ti backlight irradiated by the ninth beam of the ShenGuang II facility. The conclusion that Rayleigh - Taylor Instability went into the non-linear stage on 2.2ns has been come by the Fourier analysis of Optical thickness. For the experimental images measured under the Side-on Optical arrangement, the experimental data was smoothed by the above-mentioned method, the boundary of the image between light and shade determined by means of taking 5% of intensity values. Through fitting the curve of laser-accelerated distance, that the acceleration of the target equals 69.8μm/(ns)~2 comes into conclusion. |
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