数千电子伏特(Multi-keV)量级的X射线背光成像是高能密度等离子体物理实验中常用的一种诊断技术。在神光II激光装置上, 研究了纳秒激光驱动钛4.7 keV波段及氯2.7 keV波段背光面源的性能。研究结果表明, 氯背光能谱以类He线及类H线为主, 其中2.7 keV波段的类He-α线最强; 在当前神光II激光加载能力下, 氯背光面源相对强度超过钛背光面源一个量级, 因此, 可选用氯He-α线的X光探针进行背光诊断。

液氘在高压下有丰富的电学光学性质。利用反射率和相对介电函数关系并从广义极化角度出发初步建立了计算低Z材料电导率的简易模型; 在神光-Ⅱ装置上利用第九路激光冲击加载液氘材料并测量了其在强激光冲击下的高压状态参数和反射率。结合上述理论模型和实验, 研究了高压下液氘的电离度和电导率。结果表明, 液氘在约70 GPa时的电导率约为2.87×105 (Ω·m)-1, 已呈现出较为明显的金属电导特性。显然, 冲击加载下液氘从绝缘分子态开始电离并向金属氘转变发生在更低的压强。

利用神光Ⅱ装置上搭建的用于激光冲击波实验的温度诊断系统(该系统包括高时空分辨的扫描高温计和谱时分辨的扫描高温计)，以强激光加载铝材料冲击温度的测量，获得了铝材料冲击高温辐射发光谱的高时空分辨信号图像，结合灰体辐射理论模型，计算得到了冲击波速度19.06 km/s时铝材料的冲击温度达2.95 eV，该温度与SESAME库中冲击温度接近。研究结果表明采用该测温系统能够有效诊断金属材料的冲击温度，为后续进一步获取金属材料冲击温度数据奠定了基础。

High-power laser induced shocks were used to study spall fracture of polycrystalline aluminum at strain rates more than 106/s at “Shenguang-Ⅱ” laser facility.The free surface velocity histories of shock-loaded samples,150 μm thick and with initial temperature from 293 K to 873 K,were recorded using velocity interferometer system for any reflector(VISAR).From the free surface velocity profile ,spall strength and yield stress are calculated,which shows that spall strength declines while yield strength increases with initial temperature increasing.The loaded samples were recovered for metallographic analysis through Laser Scanning Confocal Microscopy.It is found that there are more micro-voids and more bigger voids near the spall plane.Meanwhile,the grain size increases with temperature slowly except the sharp change at 893K(near melting point).Besides,the fracture mechanisms change from mainly intergranular fracture to transgranular fracture with initial temperature increasing.

To probe the electron density distribution of the plasma,double-frequency grating shearing interferometry based on the soft X-ray laser technology is developed.The 13.9 nm Ni-like Ag soft X-ray laser is used as a probe to make attempt on the diagnosis of laser produced plasma from a planar gold wafer target.Clear interference fringes image is achieved,which fully demonstrates the practicability of this technology.However,there are some problems such as the unclear target surface in the image.Analysis indicates the main reasons of these problems and a reasonable solution is proposed to improve this technology.

An experimental research platform is built on Shenguang II high power laser facility for obtaining the equation of state of liquid deuterium which has ability to control the temperature in a range of 12–300 K with an accuracy of ±0.03 K in 80 min. By optimizing the coating processing and cleaning the target, we solve the problems that the residual reflection is too high and serious frosting takes place on the window of the target at low temperature, then we obtain the experimental image with a good signal-to-noise ratio. By using the impedance matching method and velocity interferometer system for any reflector, experimental Hugoniot data of liquid deuterium are obtained at a pressure of about 60 GPa under the output condition of 3ω, 3 ns, 1200 J on Shenguang II high power laser, which agrees well with the other published data in the same pressure regime and provides a good foundation for the next experimental study of liquid deuterium equation in 100 GPa pressure regime.

在神光-Ⅱ装置上利用强激光加载铝材料进行高应变率(高于106s-1)层裂实验,研究不同初始温度下高纯铝材料的动态损伤特性.采用任意反射面速度干涉仪测量样品自由面速度剖面,由自由面速度剖面计算纯铝样品层裂强度与屈服应力.结果表明:随着温度升高,材料层裂强度减小,屈服应力增大.对激光加载前后样品进行金相分析,观察不同初始温度下纯铝材料的微介观结构变化及其损伤特性.结果表明:随着温度升高,样品晶粒尺度缓慢增大,但在873 K(近熔点)时晶粒尺度急剧增加;层裂面附近小孔洞数目较多,孔洞尺寸也较大,而远离层裂面处,孔洞数目相对较少,且尺寸也较小;材料的断裂方式随温度升高由沿晶断裂为主逐渐变为穿晶断裂为主.

针对高温稠密激光等离子体临界密度附近电子密度的诊断需求,发展了基于软X射线激光的软X射线双频光栅干涉诊断技术.利用波长13.9 nm的类镍银软X射线激光作为探针,掠入射式的双频光栅作为分光干涉元件,对激光辐照金平面靶产生的等离子体进行诊断尝试.实验获得了清晰的干涉条纹图像,充分表明该技术的实用性.但结果中存在靶面不清晰等问题,为此,提出了初步的解决方案.

It is important to diagnose electron density of a plasma irradiated by lasers for inertial confinement fusion, in high energy density physics and related fields, especially for measuring high-Z plasma near the interface. Use of soft X-ray laser as a probe is an important method in diagnosis of plasma electron density distribution. However, it is difficult to carry out the research in high-Z laser plasma, because of the problem of excessive plasma spontaneous radiation. In view of the characteristics of soft X-ray laser, several specific experimental techniques have been developed. By using these techniques, which can greatly suppress effects of spontaneous radiation, diagnosis of high-Z plasma with soft X-ray laser probe method becomes possible. As a typical example, an experiment of diagnosing gold plasma is performed and clear images are obtained, indicating that the techniques are effective and feasible.