We measured the parameter reproducibility and radial electron density profile of capillary discharge waveguides with diameters of 650 $\mathrm{\mu} \mathrm{m}$ to 2 mm and lengths of 9 to 40 cm. To the best of the authors’ knowledge, 40 cm is the longest discharge capillary plasma waveguide to date. This length is important for $\ge$ 10 GeV electron energy gain in a single laser-driven plasma wakefield acceleration stage. Evaluation of waveguide parameter variations showed that their focusing strength was stable and reproducible to $<0.2$ % and their average on-axis plasma electron density to $<1$ %. These variations explain only a small fraction of laser-driven plasma wakefield acceleration electron bunch variations observed in experiments to date. Measurements of laser pulse centroid oscillations revealed that the radial channel profile rises faster than parabolic and is in excellent agreement with magnetohydrodynamic simulation results. We show that the effects of non-parabolic contributions on Gaussian pulse propagation were negligible when the pulse was approximately matched to the channel. However, they affected pulse propagation for a non-matched configuration in which the waveguide was used as a plasma telescope to change the focused laser pulse spot size.

中文翻译：

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长度可达 40 cm 的毛细管放电等离子体波导的径向密度分布和稳定性

我们测量了直径为 650 的毛细管放电波导的参数再现性和径向电子密度分布 $\mathrm{\mu} \mathrm{m}$ 至 2 毫米，长度为 9 至 40 厘米。据作者所知，40 cm 是迄今为止最长的放电毛细管等离子体波导。这个长度很重要 $\ge$ 在单个激光驱动的等离子体尾场加速阶段中获得 10 GeV 的电子能量增益。对波导参数变化的评估表明，它们的聚焦强度稳定且可重现 $<0.2$ % 和它们的平均轴上等离子体电子密度 $<1$ %。这些变化仅解释了迄今为止在实验中观察到的激光驱动等离子体尾场加速电子束变化的一小部分。激光脉冲质心振荡的测量表明，径向通道轮廓比抛物线上升得更快，并且与磁流体动力学模拟结果非常吻合。我们表明，当脉冲与通道近似匹配时，非抛物线贡献对高斯脉冲传播的影响可以忽略不计。然而，它们影响了非匹配配置的脉冲传播，其中波导被用作等离子体望远镜以改变聚焦的激光脉冲光斑尺寸。