Z箍缩动态黑腔阴影像诊断研究

Study of Z-pinch dynamic hohlraum shadowgraphy

为了获得填充泡沫的钨丝阵动态黑腔动力学演化图像,研究钨等离子体与泡沫柱的相互作用形式,在1MA脉冲功率装置上设计了四分幅紫外探针光(266nm)阴影成像系统,该系统时间分辨为2.5ns,静态空间分辨优于70μm,径向阴影图像展示了从固体丝膨胀消融到先驱等离子体与泡沫相互作用,从泡沫的箍缩到反弹膨胀的全过程.图像显示了在长约50ns时间内丝等离子体以"雨"的形式持续与泡沫相互作用,在整个箍缩阶段并未观察到等离子体壳层结构.定量分析表明泡沫柱的最小箍缩速度为1.0×106cm/s,最大箍缩速度为6.0×106cm/s,在轴上滞止的直径约为1mm.通过对数值模拟计算结果的讨论,明确了在Z箍缩等离子体状态下阴影成像结果主要反映了逆轫致吸收效应,与径向功率波形的时间关联给出了钨等离子体主体与泡沫柱相互作用时刻的图像.

In order to obtain the dynamic evolution image of tungsten array for foam padding, and to research the form of interaction between tungsten plasma and foam column, a shadow imaging system of four-frame ultraviolet probe laser （266 nm） is designed on 1 MA pulse power device. The time resolution of the system is 2.5 ns, and static space resolution is superior to 70 μm. The radial shadowgraphy image reveals the whole process from the melting and expansion of solid wire to the interaction between the precursor plasma and the foam, from the pinch to rebound inflation. The image shows the continuous interaction between tungsten plasma and foam in the form of Raining within a time of about 50 ns, the plasma shell structure is not found in the whole period of pinch. The quantitative analysis indicates that the minimum pinching speed of the foam column is 1.0×106 cm/s, and maximum pinching speed is 6.0×106 cm/s, and the axial stagnation diameter is about 1 mm. Shadowgram mainly shows the inverse bremsstrunlung effect of interaction between laser and plasma through simulation calculating, and main tungsten plasma interacting with foam column image is shown through synchronizing radial power profile.