The interaction of high-power short lasers with solid density targets is an important application of modern solid state lasers. However, uncertainties in measurements due to lack of information on the laser pedestal-to-peak contrast limits the validity of many conclusions. We show that X-ray spectral measurements can provide a straightforward way for accessing the laser pedestal-to-peak contrast. The experiments use silicon targets and relativistic laser intensities of 3 × 10²⁰ W/cm² with a pulse duration of 1 ps. By not using or using a plasma mirror we compare low and high contrast measurements of the Ly-α line and its satellites to show that these lines are an effective laser contrast diagnostic. This diagnostic has potential to reduce uncertainty in future laser-solid interaction studies.

高功率短激光器与固体密度靶的相互作用是现代固态激光器的重要应用。但是，由于缺乏有关激光峰峰值对比信息的测量不确定性限制了许多结论的有效性。我们表明，X射线光谱测量可以提供一种直接的方法来访问激光的峰峰值对比度。实验使用硅靶材和相对论激光强度为3×10 ²⁰  W / cm ²脉冲持续时间为1 ps。通过不使用或不使用等离子镜，我们比较了Ly-α线及其卫星的低对比度和高对比度测量结果，以显示这些线是有效的激光对比度诊断工具。这种诊断方法有可能减少未来激光与固体相互作用研究的不确定性。