发表机构
HUN-REN Wigner Research Centre for Physics（匈牙利科学院维格纳物理研究中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究用符号回归从纹影图像中提取等离子体通道参数，获得高精度解析公式，并验证了通道半径与激光能量的幂律关系，为AWAKE实验提供轻量级评估方法。
AI 中文摘要
AWAKE等离子体尾场加速实验的等离子体通道由10米长蒸气源中的铷蒸气激光电离产生。验证通道的性质——完全电离核心的半径及其边界鞘层的宽度——对于确保高质量尾场至关重要，同时验证电离脉冲传播的数值模型也很重要。近共振纹影成像可以检测低密度蒸气中的等离子体通道，但不存在直接从图像获取通道参数的逆变换方法。我们使用符号回归来寻找连接纹影信号可测量性质与等离子体轮廓参数的紧凑解析公式。利用三种不同等离子体边缘轮廓族生成的模拟信号数据库，我们获得了带有一个和两个拟合常数的公式，用于预测等效通道半径，精度优于相机像素尺寸的两倍，以及用于预测鞘层宽度的公式。用这些公式重新评估之前的测量结果，我们证实了通道半径与电离激光脉冲能量之间理论上预测的幂律关系。这些公式可通过在一组适度的新样本上重新拟合常数来适应新的实验条件，为使用深度神经网络进行评估提供了一种轻量级、可解释的替代方案。
英文摘要
The plasma channel of the AWAKE plasma wakefield acceleration experiment is created by laser ionization of rubidium vapor in a 10~m long vapor source. Verifying the properties of the channel --- the radius of its fully ionized core and the width of its boundary sheath --- that are vital for ensuring good-quality wakefields is important as is validating numerical models of ionizing pulse propagation. Near-resonant schlieren imaging can detect the plasma channel in the low-density vapor, but there is no direct inversion to obtain channel parameters from the images. We use symbolic regression to find compact analytical formulas that connect measurable properties of the schlieren signal to plasma profile parameters. Using databases of simulated signals generated with three different plasma edge-profile families, we obtain formulas with one and two fitting constants to predict the equivalent channel radius with an accuracy below twice the camera pixel size and formulas to predict the sheath width. Re-evaluating previous measurements with these formulas, we confirm a theoretically predicted power-law relationship between the channel radius and the energy of the ionizing laser pulse. The formulas can be adapted to new experimental conditions by refitting the constants on a modest set of new samples, providing a lightweight, interpretable alternative to evaluation with deep neural networks.
Comments15 pages, 7 figures
