强激光加载下金属材料微喷诊断实验研究进展

强激光加载下金属材料产生的微喷射现象及其内在的机理分析是冲击压缩科学与工程领域研究的前沿问题,相关研究对于认识材料在极端载荷条件下的动力学行为具有重要意义。近年来国内外科学家们基于各大激光装置开展了大量微喷射诊断实验研究,在喷射物性质、金属界面不稳定性增长以及微喷混合问题等方面取得了一系列重要进展。通过回顾微喷静态和动态诊断实验的研究历程,对微喷诊断实验研究方法的重要应用作了详细介绍,同时对微喷产生的主要作用机制、影响因素以及微喷混合等问题进行回顾、梳理和总结。根据当前国内外微喷诊断实验发展趋势,归纳总结目前微喷诊断实验研究结果中仍存在的不足,并对微喷射实验研究未来发展方向进行展望。     

SILEX-1装置上等离子体尾场加速电子初步实验

激光等离子体加速电子机制可以产生准单能的高能电子束, 近年来成为国际上的研究热点. 中国工程物理研究院激光装置已经能够达到286TW的输出功率, 为国内在该领域的研究提供了实验条件. 文章介绍了在SILEX-1装置上开展的激光等离子体加速电子的初步实验, 并对测得结果进行讨论, 为下一步实验的进行提供了准备条件.     

Deuterium cluster jet produced at moderate backing pressures

A deuterium cluster jet produced in the supersonic expansion into vacuum of deuterium gas at liquid nitrogen temperature and moderate backing pressures are studied by Rayleigh scattering techniques. The experimental results show that deuterium clusters can be created at moderate gas backing pressures ranging from 8 to 23 bar, and a maximum average cluster size of 350 atoms per cluster is estimated. The temporal evolution of the cluster jet generated at the backing pressure of 20 bar demonstrates a two-plateau structure. The possible mechanism responsible for this structure is discussed. The former plateau with higher average atom and cluster densities is more suitable for the general laser-cluster interaction experiments.     

Self-Injection and Acceleration of Monoenergetic Electron Beams from Laser Wakefield Accelerators in a Highly Relativistic Regime

Self-injection and acceleration of monoenergetic electron beams from laser wakefield accelerators are first investigated in the highly relativistic regime, using 100 TW class, 27 fs laser pulses. Quasi-monoenergetic multi- bunched beams with energies as high as multi-hundredMeV are observed with simultaneous measurements of side-scattering emissions that indicate the formation of self-channelfing and self-injection of electrons into a plasma wake, referred to as a ＇bubble＇. The three-dimensional particle-in-cell simulations confirmed multiple self-injection of electron bunches into the bubble and their beam acceleration with gradient of 1.5 GeV/cm.     

气体靶密度的数值计算与实验研究

 采用了1维简单模型来模拟气体靶的空间密度分布情况，并且该计算值得到了实验的验证。使用M-Z干涉仪诊断锥型喷嘴喷射的气体靶密度分布，得到了不同压力和不同延时下的干涉图样。自行编写了实验数据处理程序，得到了不同情况下气体密度的空间分布。在相互作用实验中，由气体分子密度随压力的变化，可以确定合适的压力，以获得预期的气体靶密度；由气体分子密度随时间的变化，可以确定激光与气体的作用时刻。     

激光驱动气库靶对铝的准等熵压缩实验研究

利用激光驱动气库材料形成的等离子体射流对材料进行斜波加载, 可以获得高应变率的准等熵压缩. 在神光III 原型高功率激光装置上开展了激光驱动铝材料的准等熵压缩实验, 成像型速度干涉仪VISAR记录到样品自由面连续、光滑的速度历史, 采用反积分法得到60 GPa以上的峰值压强, 加载上升沿约10 ns,应变率可达10⁸ s ^-1, 并且观察到了压缩波在样品后表面的反射效应.     

Characterization of relativistic electrons generated by a cone guiding laser pulse

We demonstrated the interaction of a gold cone target with a femto second(fs) laser pulse above the relativistic intensity of 1.37×10 18 μm 2 W/cm 2.Relativistic electrons with energy above 2 MeV were observed.A 25%-40% increase of the electron temperature is achieved compared to the case when a plane gold target is used.The electron temperature increase results from the guiding of the laser beam at the tip and the intense quasistatic magnetic field in the cone geometry.The behavior of the relativistic electrons is verified in our 2D-PIC simulations.     

超强超短脉冲激光诱发大尺度氘团簇聚变

 利用低温脉冲气阀获得了平均含有3×103氘原子的氘团簇。在飞秒激光装置上实现了氘团簇聚变，每发中子产额为1×10³。中子产额对激光功率密度敏感，保持激光能量不变，随着激光焦斑的变大，DD聚变中子产额逐渐增加，最大值出现在激光焦斑为470 mm时;继续增大激光焦斑，没有观察到中子信号。实验结果还表明激光氘团簇聚变发生的区域主要是激光辐照的等离子体热区，此区域内邻近氘团簇库仑爆炸发射的高能氘离子碰撞引发聚变反应。     

Growth of deuterium clusters in a gas jet and ion energy spectrum of clusters in ultra-short laser field

Large deuterium clusters are generated using a cryogenic pulse valve with a cone nozzle (21 mm long, 4° open angle). Rayleigh scattering experiment is carried out to obtain the scaling relation between scattering signal SR and backing pressure P0. A method using the Coulomb explosion model is proposed to verify that the clusters continue to grow after their leaving the nozzle. Our experiments suggest a tentatively optimized position for laser cluster interaction.     

SILEX-I装置上激光-团簇聚变实验中子产额测量

 超短超强脉冲激光与CD4团簇相互作用可以产生高能量的氘离子,从而产生DD聚变中子,这种团簇聚变中子源有着非常广阔的应用前景。在SILEX-I 100 TW飞秒激光装置上,超短超强脉冲激光与CD₄团簇相互作用实现了DD核聚变。团簇聚变的中子产额是实验中最为重要的物理量,在实验中采用高灵敏的中子探测器对团簇聚变产生的中子进行了测量,在现有实验条件下测得中子产额为10³。