A method was developed with laser-irradiated Au planar foils to characterize the focal spot of UV laser beams on a target at full energy from soft x-ray emission. A pinhole camera with a back-thinned charge-coupled device detector and filtration with thin Be and Al foil filters provides images of the x-ray emission at photon energies <2 keV. This method requires a careful measurement of the relationship between the applied UV fluence and the x-ray signal, which can be described by a power-law dependence. The measured exponent γ ∼ 2 provides a dynamic range of ∼25 for the inferred UV fluence. UV fluence profiles of selected beams were measured for 100-ps and 1-ns laser pulses and were compared to directly measured profiles from an UV equivalent-target-plane diagnostic. The inferred spot size and super-Gaussian order from the x-ray technique agree within several percent with the values measured with the direct UV measurements.

中文翻译：

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从 OMEGA 上的软 X 射线针孔相机测量推断出的紫外线通量焦斑轮廓

开发了一种方法，使用激光照射的 Au 平面箔来表征紫外激光束在软 X 射线发射的全能量下在目标上的焦斑。带有背面变薄的电荷耦合器件检测器和用薄 Be 和 Al 箔过滤器过滤的针孔相机可提供光子能量 <2 keV 的 X 射线发射图像。这种方法需要仔细测量应用的 UV 能量密度和 X 射线信号之间的关系，这可以用幂律相关性来描述。测得的指数 γ ∼ 2 为推断的 UV 通量提供了 ∼25 的动态范围。针对 100 ps 和 1 ns 激光脉冲测量选定光束的 UV 能量密度分布，并将其与来自 UV 等效目标平面诊断的直接测量分布进行比较。