Magnetic reconnection (MR) is a universal physical process in plasma, in which the stored magnetic energy is converted into high-velocity flows and energetic particles. It is believed that MR plays an important role in many plasma phenomena such as solar fare, gamma-ray burst, fusion plasma instabilities, etc.. The process of MR has been studied in detail by dedicated magnetic-driven experiments. Here, we report the measurements of magnetic reconnection driven by Shenguang II lasers and Gekko XVII lasers. A collimated plasma jet is observed along the direction perpendicular to the reconnection plane with the optical probing. The present jet is very different from traditional magnetic reconnection outflows as known in the two-dimensional reconnection plane. In our experiment, by changing the delay of optical probing beam, we measure the temporal evolution of jet from 0.5 ns to 2.5 ns and its velocity around 400 km/s is deduced. Highcollimated jet is also confirmed by its strong X-ray radiation recorded by an X-ray pinhole camera. With the help of optical interferograms we calculate the jet configuration and its density distribution by using Abel inverting technique. A magnetic spectrometer with an energy range from hundred eV up to one MeV is installed in front of the jet, in the direction perpendicular to the reconnection plane, to measure the accelerated electrons. Two cases are considered for checking the acceleration of electrons. The results show that more accelerated electrons can be found in the reconnection case than in the case without reconnection. We propose that the formation and collimation of the plasma jet, and the electron energy spectrum may be possible directly influenced by the reconnection electric field, which is very important for understanding the energy conversion in the process of MR and establishment of the theoretical model. Finally the electron energy spectra of three different materials Al, Ta and Au are also shown in our work. The results indicate that the higher atomic number material can obtain a better signal-noise ratio, which provides some helpful references for our future work.

利用“神光Ⅱ”激光装置的两束激光烧蚀半圆柱壳层靶产生了高速等离子体喷流。喷流的参数由光学和X射线诊断测量。喷流是准直的,在真空中传播。一维流体力学模拟被用来间接地计算喷流的速度。喷流的准直可能来源于高Z等离子体的辐射冷却。由于和年轻恒星喷流具有某些几何相似性,实验室喷流对于在实验室中模拟年轻恒星喷流具有潜在应用。

在超短超强激光与固体薄膜靶相互作用研究中, 实验上首次观测到了沿靶面方向发射的高能超热电子束。该电子束只有在等离子体电子密度标长较短的条件下才会出现。理论模拟表明, 靶表面电磁场的约束作用是产生此电子束的主要原因。这一结果有助于加深对激光惯性约束聚变快点火实验中的锥靶物理过程的理解, 并有潜在的应用前景。

对超强飞秒激光在空气中传输形成等离子体通道进行了系统研究。空气中长等离子体通道的形成主要是由于光学克尔自聚焦效应，等离子体散焦作用和光束衍射之间达到了动态平衡，使超强飞秒激光脉冲在空气中形成数百米长甚至千米量级长度的等离子体通道。我们发展了通道的四种主要诊断方法：声学诊断、荧光探测、电阻率测量和横截面成像方法，这几种方法各有优势，可以互为补充．研究了通道同时伴随的三次谐波辐射，三次谐波具有与基频激光相似的变化规律。从应用角度出发，我们对通道内细丝进行了优化控制，对通道寿命的延长进行了研究，使通道寿命达到了微秒量级。改变激光脉冲的初始啁啾，得到了更远距离处的稳定成丝分布，和最优化的超连续光谱产生，此外，还介绍了激光诱导高压放电的应用研究。