A recent experiment on the Shenguang III laser facility has applied open-end gold hohlraums with two gas pressures to study the movement of a plasma bubble. Under a laser intensity and width close to those of an ignition main pulse, the bubbles possess radial scales from several hundred to one thousand micrometers. An x-ray framing camera is used to measure the N-band x-ray images generated from the gold bubble plasma at different moments, from which the edge positions of the expanding bubbles are accurately acquired. The experimental results are simulated by an optimized two-dimensional radiation hydrodynamic code. Based on the classical average atom (AA) model, two phenomenological coefficients Cer and Cop are introduced into the code to correct the bubble evolution. Cer artificially redistributes the energies between radiation and matter, and Cop correlatively adjusts the plasma opacity. The bubble movement simulated by the novel phenomenological model agrees better with the measured result than that by the AA model. This work plays a critical role in our code improvements and advances the reliability of the hohlraum design.
神光III激光装置上的一项近期实验采用了具有两种充气压力的开端金黑腔，以研究等离子体泡的运动。在接近点火主脉冲的激光强度与脉宽条件下，这些等离子体泡的径向尺度可达数百至一千微米。实验中使用X射线条纹相机在不同时刻测量金等离子体泡产生的N带X射线图像，并据此精确获取了膨胀等离子体泡的边界位置。实验结果通过一个二维辐射流体力学程序进行了模拟。基于经典平均原子（AA）模型，在该程序中引入了两个唯象系数Cer和Cop以修正等离子体泡的演化过程。其中，Cer人为地重新分配辐射与物质之间的能量，而Cop则相应调整等离子体的不透明度。采用这一新型唯象模型所模拟的等离子体泡运动与实测结果相比，较AA模型具有更好的一致性。这项工作对我们程序的改进起到了关键作用，并提升了黑腔设计的可靠性。