Shaped Pulse Laser-driven One-dimensional Compression Of The Ch Planar Target

One of the fascinating goals is to obtain pure fusion energy, for several decades a great number of scientists devote themselves into this area. Inertial confinement fusion (ICF) is an approach to controllable fusion. It is prospected to solve the problem of energy entirely. It must be overcome that the DT fuel is confined to high density by laser. High density and stable implosion requirements can be achieved by shaping the laser pulse.Taking into account the limitations of our laser facility, target making and diagnosis, and also for better understanding of physical process, compression of planar target other than spherical shell is studied, which can be used as a reference for implosion. So the simulation that the planar CH targets are compressed one dimensionally by shaping pulse has been done with MULTI code. The experiment has been carried out on Shenguang-II laser facility. It has been investigated that the effect of the pulse shape on compressed density of the planar CH target, laser imprinting, and Rayleigh-Taylor (RT) instability.This thesis is organized in six chapters. At first, we introduce briefly the concepts of ICF, review the progress on it.In chapterâ…¡, we analyze the principle of designing the laser pulse shape which is used to drive the implosion. According to the ninth laser beam of Shenguang-II, The simulation conditions of MULTI are decided. The one-dimensional (1D) compression of the single layer CH targets and the three layers targets driven by Multi-shaping pulses has been simulated. The simulation indicates that the compression driven by the rise-pulse is the best. If lowering the initial density of the CH targets, the density contrast driven by two different shaping pulses will be more notable. According to the simulation, we chose the pulse shape which will be used in experiment.In chapterâ…¢, we introduce the 1D compression experiment. By making use of the pinhole-assisted point projection radiograph system, we have gotten the radiographs of the single layer planar CH targets and the three layers planar CH targets driven by shaping pulse. After data processing, we have obtained the density distribution of the compressed CH targets. On the condition that the laser energy is the same, rise-pulse can compress the CH targets to higher density. We re-simulate the compression using the conditions of experiment. The simulation results do not agree well with experimental results. We also analyze the interfaces appearing in the side-on radiograph which relate to the 1D compression. Finally, we present some ideas for next experiment.In chapterâ…£, we introduce the investigation on laser imprinting and consequent instability growth. While the initial laser intensity is low, the laser imprinting and consequent RT instability growth is large. On the condition that the laser has the same energy, the modulation depth irradiated by the trapezoid-pulse is the least (modulation depth a = 4.5±1μm), the modulation depth irradiated by the no-picket rise-pulse is the largest (modulation depth a = 15±1μm). The intensity of the pick has large effect on the modulation depth caused by laser imprinting. In our experiment, while irradiated with a picket rise- pulse which picket intensity equal to the intensity of the main pulse, the modulation depth decrease from a =15±1μm (no picket) to a = 6±1μm. While the laser intensity is high enough, the non-local electron will affect the RT instability growth. In our experiment, when the laser intensity reaches 8×10¹³W/cm², the modulation caused by irradiating non-uniformly disappears.In chapterâ…¤, we introduce the high resolution imaging system using in accurate measurement of compression. Because of the low resolution of the pinhole radiograph system, the error of our data is big. So we have studied the high distinguish image system. Experimental results show that 1D KBA imaging system helps to increase the resolving power. The resolution (out-line) of the KBA is 2～3μm . On-line experiment reviewed, the resolution is 4.1μm. Furthermore, the grazing-incidence mirror of the imaging system is coated with narrow-band-high-reflection film, which can reduce the intensity of non-work light. So the Signal-to-Noise of the image will be better than that of the pinhole radiograph system.In chapterâ…¥, a conclusion and some ideas for next experiment are presented.