“四靶串接”类氖锗软X光激光趋向饱和增益的理论研究

介绍了“四靶串接”设计思想,继对接方式之后,又提出了顺接方式来提高X光激光增益,使四靶总长度达到5.6cm。我们研制了程序系列来模拟这一实验,直接给出测点处的X光激光的强度。先用上轮“双靶对接”实验结果检验我们的程序系列,使得23.2nm激光线的结果与实验数据相符合,再用它模拟“四靶串接”实验。在实验之前,对各靶之间距离和角度,以及这些数据对实验结果的敏感程度作了预估,用以指导实验。实验结果证明理论模拟是正确的。23.2nm和23.6nm两条激光线已明显趋于饱和,其小讯号增益长度积GL分别达到18.3和17.6,有效GL分别达到16.4和15.7。X光激光的发散角已减小到3～4mrad,超过美国利弗莫尔实验室(LLNL)已发表的最好结果。

LASER IN NEON-LIKE GERMANIUM PLASMAS

In order to prevent the laser beam from being refracted out of lasing medium, we proposed and carried out a novel design named double -target opposing coupling early 1990. We developed opposing coupling idea and proposed following coupling idea for four -target series coupling experiments early 1991. The total length for four targets is up to 5.6cm. We have developed a series of codes, which can simulate the laser-produced plasma condition, population inversion, gain of laser lines , and propagation and amplification of laser lines in lasing medium. Before these four-target series coupling experiments, we adjusted some parameters in JB19 and ALPHA codes in order to match the results of last double -target opposing coupling experiments. The results of simulation for laser line of 23.2nm agree with those of the last round experiment. Then we simulate this round of experiment and get the parameters of the distance and angle between the targets in order to get best coupling. The results of the experiments show that the simulation is good. The gain length product(GL) of small signal is up to about 18 for both lines at 23.2 and 23.6 nm, and the effective GL is 16.4 and 15.7 for these two lines, respectively. These two lines are obviously tending to saturation. The divergence of laser beams reduces to 3 ~4 mrad.