Study On The Simulation Experiment Of Stimulated Raman Scatteriing Of High-power Laser Beam In Long Path

Inertial confinement fusion(ICF) provides a new scheme to solve the human energy crisis. To realise the ICF, technical indicators of ICF become increasingly higher including diameter, light intensity and flux are with increasing installation size. Enormous scale of apparatus leads to the long distance transmission in air, which excites stimulated rotational Raman scattering(SRRS). SRRS will consume the energy of main beam, reduce beam power density and increase the beam divergence angle, which may result in the failure of fusion ignition. So the study of the SRRS mechanism of generation factors and amplification is of great significance for ICF.In this investigation, we study the SRRS theoretically and experimentally. Firstly, we establish the SRRS physical model numerically and calculate the SRRS parameters of 1 w and 3 w pulses respectively, like threshold and its increasing law of high power laser in air, as well as the generation factor. Secondly, in order to test the correctness of the theoretical model, we build the stimulated vibration Raman scattering(SVRS) experimental platform with high-pressure hydrogen as the active medium to simulate the SRRS of high power laser in air. Although SVRS and SRRS have different transition levels, the physical process of can be described in the same model. The feasibility of this simulation is proved by the experimental SVRS threshold and transformation efficiency and the veracity of numerical model is verified experimentally. Finally, inadequacy of the experiment and the following improvement are analyzed. To verify the impact of the spatial characteristics on the stimulated Raman scattering, we design an experiment scheme to test effect of near field laser beam on SVRS with high pressure hydrogen as the medium. Experimental scheme based on the hundred Joule laser system in Harbin Institute of Technology(HIT). By using the parameter of the hundred Joule laser system, we calculate the impact of the spatial distribution on SVRS and achieve the near-field change led by SRRS of non-uniform distribution of beam. The change regulation of the beam near field and flux regulation of Stokes under different light conversion efficiency is achieved.