基于神光Ⅱ升级装置,研究了纳秒/皮秒双束激光联合驱动双层靶的伽马(γ)辐射特征。利用ns束激光与CH薄膜靶相互作用,产生大尺度近临界密度等离子体,然后将ps束激光作用在该等离子体上,产生高能电子,高能电子穿过2 mm厚的Au靶,通过轫致辐射产生γ射线。对不同方向的γ辐射能谱和靶室外的γ辐射剂量分布进行实验测量,发现γ辐射集中在激光前冲方向,具有较小的发散角,而且在该方向上高能段的γ辐射较强。这说明双层靶的设计可以提高ps束激光与等离子体的能量耦合效率,提高高能电子温度,增加高能电子数目,有利于高能段γ辐射在ps束激光的前冲方向集中。另外,在靶室外距离靶点1.25 m处测到的50 keV以上γ辐射的单发次最大剂量为277 μGy。本研究结果对γ辐射的防护和应用具有参考价值。

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.

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.

The fabrication of metal film steps used in equation of state experiment targets was investigated. The metal film step of hundreds of microns width was cut by picosecond laser processing technology. The factors of generating heat effect in the processing were analyzed. The processing parameters were as follows: power 0.5 W, pulse width 10 ps, wavelength 355 nm, and scanning speed 100 mm/s. Two metal films of 400 and 120 microns width were obtained in the experiment. The measurement results show that the width of metal film can be precisely controlled and the quality of metal film surface before and after cutting was the same.

介绍了激光状态方程靶中金属薄膜台阶的切割方法。采用皮秒激光加工技术切割了宽度百μm量级的金属薄膜台阶, 研究了金属薄膜台阶宽度控制的方法, 讨论了切割过程中产生热效应的因素, 优化了激光加工参数。实验加工中, 采用加工的参数: 功率为0.5 W, 脉宽10 ps, 波长355 nm, 扫描速率为100 mm/s, 获得了宽度400 μm和120 μm的金属薄膜。测量结果表明, 金属薄膜的宽度能精确控制, 切割后金属薄膜表面质量能保持切割前的质量。

Direct-drive and indirect-drive inertial confinement fusion (ICF) targets use temporally shaped drive pulses to optimize target performance. The timing of multiple shock waves is crucial to the performance of ICF ignition targets. Velocity interferometer system for any reflector (VISAR) is the principal diagnostic tool for shock-timing experiments. We present velocity measurements from the shock waves in polystyrene targets driven by two 200-ps pulses separated by 1–2 ns. These pulses drive two shock waves that coalescence in the target. Coalescence time and transit times are observed by VISAR.