两级喇曼压缩系统配偏振干涉仪诊断等离子体电子密度

Plasma electron density diagnosis by Nomarski interferometer with Raman compression cascade system

在星光Ⅱ铷玻璃激光装置上,采用两级喇曼压缩系统产生的波长为308nm的紫外光作为探针束,配合Nomarski偏振干涉仪对金平面靶冕区激光等离子体进行诊断。308nm光具有波长短、亮度高、脉冲时间短、相干性好的优点,作为探针束诊断冕区产生的等离子体电子密度,可以与高功率激光装置打靶激光同步,实现有效地脉冲压缩,同时避免等离子体中谐波分量的干扰。实验获得了308nm紫外探针光偏振干涉条纹图,在研究Abel反演算法的基础上,利用自行研制的基于Windows操作系统的实验数据处理软件,对实验数据进行了处理和分析,得到了冕区等离子体电子密度的空间分布。结果表明两级喇曼压缩系统配偏振干涉能有效抑制主束谐波影响,以更高时间分辨测量等离子体的更高密度区域。

Nomarski interferometer is an effective measurement to diagnose the electron density of laser-produced plasma. Using Raman compression cascade system with 1054 nm incident light, a probe beam that has a 308 nm wavelength, 28 ps pulse duration and 1 mJ energy was obtained. The probe beam was applied in the polarization interferometry to measure the electron density of Au plasmas produced by 527 nm main beam at Xingguang-II facility. The measured interferograms were analyzed to obtain the two-dimension profile of electron density. The result shows that with the aid of the probe beam, the electron density can be probed with a much higher temporal resolution and the disturbance of harmonic can be effectively avoided.