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为研究激光等离子体冲击波力学效应受入射激光及环境因素的影响,利用波长1．06μm,脉冲能量320 mJ,脉宽10 ns的Nd;YAG激光作用在Al靶上,研究了冲量耦合系数(C_m)和离焦量(Z)之间的关系。实验发现在1．01×10~5 Pa情况下,初始时C_m随Z增大而增大,到Z=-12 mm附近达到最大值;而后C_m随Z增大而减小。在4000 Pa时,C_m随Z的变化关系与1．01×10~5 Pa时相似,但峰值位置后移。离焦量不同时,由于作用激光的功率密度不同而影响等离子体屏蔽效果;光斑大小不同将影响稀疏波作用,且离焦量正负不同时激光等离子体冲击波对靶的作用机制也明显不同,这些因素决定了离焦量对等离子体冲击波力学效应的影响。
In order to study the mechanical effects of laser shock wave by incident laser and environmental factors, Nd: YAG laser with wavelength of 1.06μm, pulse energy of 320 mJ and pulse width of 10 ns was used on Al target. Impulse coupling coefficient (C_m ) And the amount of defocus (Z). The experiment shows that in the case of 1.01 × 10 ~ 5 Pa, the initial C_m increases with increasing Z, reaches the maximum around Z = -12 mm; then C_m decreases with Z increasing. At 4000 Pa, the relationship between C_m and Z is similar to 1.01 × 10 ~ 5 Pa, but the peak position is shifted backward. When the defocus amount is different, the plasma shielding effect will be affected due to the different laser power densities; the different spot sizes will affect the effect of the sparse wave, and the mechanism of laser plasma shock wave on the target is obviously different when the defocus amount is different. These factors determine the effect of defocus on the plasma shock wave mechanical effects.