毛细管放电69.8nm激光强度空间分布特性研究

报道了毛细管放电69.8 nm软X射线激光的光强分布特性. 实验中所用毛细管长度为35 cm, 放电主脉冲电流幅值为11.5 kA, 放电初始气压为14-16 Pa. 测得的光斑强度分布由两部分构成, 在中心有一个占光强绝大部分的主峰, 其发散角约为0.4 mrad, 边缘还有两个小的离轴峰, 峰-峰发散角约为1.5 mrad. 理论上采用几何光学近似的方法对其光强分布进行计算, 光斑如此小的发散角主峰的出现, 可能主要是由于毛细管放电过程中电子密度在轴心处具有轻微凹陷造成的.

Intensity distribution of 69.8 nm laser pumped by capillary discharge

In this paper, intensity distribution of 69.8 nm soft X-ray laser pumped by capillary discharge is studied theoretically and experimentally. In experiment, a main current of 11.5 kA is chosen to generate the plasma in a 35 cm long capillary filling with Ar at pressures in a range of 14-16 Pa. The intensity distribution is characterized by two different components. There is a big peak in the center of the intensity distribution profile, and its full width at half maximum divergence is about 0.4 mrad. There are also two small off-axis peaks on the either side of the center peak, and the peak-to-peak divergence is about 1.5 mrad. In theory, three different distributions of electron density are used to study the propagation of Ne-like Ar 69.8 nm laser in a cylindrical plasma column. The spatial intensity distribution for the 69.8 nm laser beam is calculated with the geometrical optics approximation. The results show that the center peak, which has such a small divergence, could be attributed to the slight depression of electron density on the axis.