不可再生能源将在数十至数百年内耗竭，人类将会面临世界性的能源危机。受控核聚变是克服能源危机的理想的终极解决方案，而Z-pinch驱动的X射线惯性约束聚变正是实现可控核聚变的可能途径之一。相关研究发现，由大量(几百根)金属细丝(微米级)组成的圆筒状丝阵Z-pinch负载能够实现良好的能量转换效率和X射线辐射功率。但是丝阵Z-pinch负载还存在很多问题，尤其是丝阵Z-pinch的早期过程，对能量转换效率和X射线辐射功率有非常重要影响。本论文基于脉冲功率装置PPG-1对丝阵Z-pinch早期过程进行了X射线背光成像研究。设计了4种不同的背光成像光路布置，来获得不同的背光图像。利用已知厚度的阶梯光楔，测定电爆炸金属丝质量面密度的分布。以往的研究对丝阵Z-pinch背光图像主要是进行定性描述以及少量零星的定量结果。本文系统地提出丝阵Z-pinch早期过程背光图像的定量分析方法，包括基于图像灰度和基于图像对应的质量面密度的两种分析方法。对于不涉及质量密度的参数，两种方法得到的结果基本一致。基于阶梯光楔标定，得到了时间分辨的单丝电爆炸等离子体质量面密度的空间分布图，丝芯的剥离质量和质量剥离率，沿丝长度方向平均的质量面密度分布曲线。对平均质量面密度分布进行阿贝尔逆变换，得到了单丝电爆炸等离子体质量体密度径向分布。利用上述定量分析方法，对(单丝、双丝、平面四丝)丝阵Z-pinch早期过程的背光图像进行全面的分析。对于流经电流相近的单丝Z-pinch，同种材料的电爆丝直径越大，膨胀速度也越大；高电导率的电爆丝的膨胀率明显大于低电导率的电爆丝；首次测算得金、银、铜的主导不稳定性波长；基于实验得到的质量体密度径向分布曲线，确定了冷丝起始的单丝电爆炸模型中Spitzer电阻率的修正系数；通过实验和仿真相互印证，解释了质量体密度径向分布存在局部峰值的现象。基于双丝Z-pinch背光图像，首次观察到并详细描述了先驱等离子体柱的螺旋不稳定性结构，并发现同种材料的双丝直径越小，两丝的膨胀程度越接近。平面四丝Z-pinch的外侧丝膨胀率总是大于内侧丝膨胀率。首次在接近实际情况的大电流下研究了镀膜对电爆丝的影响。镀膜总体上可使电爆丝膨胀倍数增加，但增大倍数因材料而异。双丝Z-pinch的轴向背光图像的定量分析显示晕层等离子体的向心运动可分为先慢后快两个阶段。
Non-renewable energy will be depleted in the tens to hundreds of years, thus, mankind will face a worldwide energy crisis. Controlled nuclear fusion is an ideal and ultimate solution to overcome the energy crisis. Z-pinch-driven x-ray inertial confinement fusion is one of the possible approaches to achieve controlled nuclear fusion. Related studies have found that the cylindrical wire array Z-pinch load with large number (~100) of metal filaments (~μm) can achieve a good energy conversion efficiency and power of X-ray radiation. However, there are still many problems in the wire array Z-pinch load, especially the problems in the early stage of wire array Z-pinch, which have a very significant impact on the energy conversion efficiency and X-ray radiation power.In this paper, the early stage of wire array Z-pinch was investigated by x-ray backlighting using an X-pinch as the x-ray source. Based on the pulsed power generator PPG-I (400kA/500kV/100ns), four different backlighting arrangements were designed to obtain different backlight images. Plasma density distribution of electrical explosion of wire array Z-pinch was calibrated with a step wedge. Previous results from the backlight image of wire array Z-pinch are mostly qualitative and seldom quantitative. This dissertation proposed a quantitative method to analyze the backlight image of the early stage of wire array Z-pinch, including the method based on the grayscale and the method based on mass density corresponding to the grayscale. For the parameters do not involve mass density, the results obtained by these two methods are basically the same. Based on the calibration with the step wedge, the time-resolved three-dimensional pictures of mass density distribution of single-wire electrical explosion were obtained. With these pictures, the physical parameters such as the ablated mass, the mass ablation rate and the average areal mass density were determined. The radial distribution of the plasma mass density from single-wire explosion was obtained by Abel inversion of the areal mass density curve.The backlight images of wire array (single-wire, double wire, planar four-wire) Z-pinch in the early stage were analyzed with the quantitative analysis method mentioned above. For single-wire made from the same material, the wire with a larger diameter has a faster expansion speed, when the current is kept almost the same. Expansion rate of the highly conductive wire is much higher than that of the lowly conductive wire. The dominant wavelengths of plasma instability for gold, silver and copper were determined for the first time. Based on the radial distribution of the plasma mass density determined from the backlighting images, the correction was made on the Spitzer resistivity used in the numerical model of single-wire electrical explosion. The phenomenon of local peak in the radial distribution of the plasma mass density was explained.Based on the double-wire Z-pinch backlight images, the structure of spiral instability in the precursor plasma column was observed and described in detail for the first time. It was found that, for the wires made from the same material, the smaller the wire diameter is, the more uniformly the two-wire expand. For the planar four-wire Z-pinch，the expansion rate of the external wires is always higher than that of the inner wires. The experiments on the electrical explosion of the wires coated with Polyimide with a high current of 45kA/wire were carried for the first time to study the influence of the coating on the wire explosion. Generally speaking, wire coating could increase the expansion rate of the exploding wire, but the extent of this increase depends on the wire material. The axially backlighting images of double-wire Z-pinch show that the movement of the coronal plasma can be divided into two stages: slow stage and fast stage.
