Laser-heated capillary discharge waveguides are novel, low plasma density guiding structures able to guide intense laser pulses over many diffraction lengths and have recently enabled the acceleration of electrons to 7.8 GeV by using a laser-plasma accelerator (LPA). These devices represent an improvement over conventional capillary discharge waveguides, as the channel matched spot size and plasma density can be tuned independently of the capillary radius. This has allowed the guiding of petawatt-scale pulses focused to small spot sizes within large diameter capillaries, preventing laser damage of the capillary structure. High performance channel-guided LPAs require control of matched spot size and density, which experiments and simulations reported here show can be tuned over a wide range via initial discharge and laser parameters. In this paper, measurements of the matched spot size and plasma density in laser-heated capillary discharges are presented, which are found to be in excellent agreement with simulations performed using the MHD code MARPLE. Strategies for optimizing accelerator performance are identified based on these results.

中文翻译：

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激光加热毛细管放电波导作为激光等离子体加速的可调结构

激光加热毛细管放电波导是一种新颖的低等离子体密度引导结构，能够在许多衍射长度上引导强激光脉冲，并且最近通过使用激光等离子体加速器 (LPA) 能够将电子加速到 7.8 GeV。这些设备代表了对传统毛细管放电波导的改进，因为通道匹配的光斑尺寸和等离子体密度可以独立于毛细管半径进行调整。这允许将拍瓦级脉冲引导到大直径毛细管内的小光斑尺寸，防止激光损坏毛细管结构。高性能通道引导 LPA 需要控制匹配的光斑尺寸和密度，这里报告的实验和模拟表明，可以通过初始放电和激光参数在很宽的范围内进行调整。在本文中，介绍了激光加热毛细管放电中匹配光斑尺寸和等离子体密度的测量值，发现这些测量值与使用 MHD 代码 MARPLE 进行的模拟非常吻合。根据这些结果确定优化加速器性能的策略。