利用有限元方法数值模拟了单晶硅(Si)、铜(Cu)、钨(W)、氧化铍(BeO)等镜体材料的热畸变特性.结果表明:当入射激光功率为2 kW、镜面反射率为93%、光斑直径为17 mm、激光照射时间为10 s时,四种材料基板的中心最大热变形分别为0.984,3.32,1.55,1.88 μm.相比之下,Si镜的热变形最小,是比较理想的镜体材料;Cu镜的热变形最大;W和BeO两种材料的镜热变形介于Si镜和Cu镜之间,具有较高的强度和硬度,抗破坏能力较强.

The thermal distortions of mirror substrates with such materials as silicon, copper, tungsten and beryllium oxide are calculated and analyzed by use of finite element methods. The results show that when the power of input laser with the diameter of 17 cm gets up to 2 kW, and the reflectivity of the mirrors is 93%, the central maximum thermal distortions of the mirror substrates are separately 0.984 μm, 3.32 μm, 1.55 μm and 1.88 μm, respectively, under the radiation time of 10 seconds. By comparison, the thermal distortion of silicon substrate is the smallest, which would be a kind of more promising material for mirror substrates. And the thermal deformation of Cu substrate is the largest, while those of W and BeO are between Si and Cu. But the materials of W and BeO have high force intensity, flexural rigidity, and great anti-destructive capability.