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针对间接驱动装置中球形腔结构及其光路排布,并基于光谱角色散、连续相位板(CPP)和偏振控制板联用的束匀滑方案,建立了球形腔内激光束的传输模型。由于球形腔和光路排布的高度球对称性,在对激光束经过注入孔的传输特性进行分析时,选取注入孔所在平面作为观察面,并主要对其“堵孔”问题进行分析;在对腔内的传输及腔壁的辐照特性进行分析时,选取了一系列同心球面作为观察面,以分析其均匀性。计算结果表明当不同入射角度的激光集束采用相同的CPP设计时,随集束入射角度的增大,在注入孔处,激光的注入率降低,更易导致“堵孔”现象,但激光集束在腔内的交叉重叠会逐渐减少,其在腔壁上的光斑均匀性有所改善,且整体光斑的占空比较有所提高,更利于靶丸均匀辐照。当不同入射角度的激光集束采用不同的CPP来优化光斑时,在注入孔的“堵孔”问题得到改善,而腔壁的占空比有所降低。在实际工作中,应综合考虑注入孔的注入率和堵孔问题、腔内的交叉、腔壁上的光斑均匀性及占空比,对球形腔中集束的入射角度进行合理设计。
Aiming at the spherical cavity structure and its light path arrangement in the indirect driving device, the transmission model of the laser beam in the spherical cavity was established based on the beam smoothing scheme of spectral dispersion, continuous phase plate (CPP) and polarization control plate. Due to the highly spherical symmetry of the spherical cavity and the optical path, the plane of the injection hole is selected as the observation surface when analyzing the transmission characteristics of the laser beam passing through the injection hole, and the problem of “plugging holes” is mainly analyzed. In the analysis of the transmission in the cavity and the radiation characteristics of the cavity wall, a series of concentric spherical surfaces were selected as observation surfaces to analyze their uniformity. The results show that when the laser beams with different incident angles adopt the same CPP design, the laser injection rate decreases with the increase of incident angle of the laser beam, which is more likely to result in the phenomenon of The intracavity cross overlap will gradually decrease, the uniformity of the spot on the cavity wall will be improved, and the overall spot duty cycle has been improved, which is more conducive to uniform irradiation of the target. When different CPPs are used to optimize the laser spot at different angles of incidence, the “plugging hole” problem in the injection hole is improved and the duty cycle of the cavity wall is reduced. In practical work, the injection rate and plugging holes of the injection hole, the cross in the cavity, the uniformity of the spot on the cavity wall and the duty ratio should be considered in order to rationally design the incident angle of the bundle in the spherical cavity.