Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy.
Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy.
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DOI：
10.1063/1.4913585
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发表时间：
2015-03
期刊：
影响因子：
--
通讯作者：
Ullom JN
中科院分区：
文献类型：
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作者：
Miaja-Avila L;O'Neil GC;Uhlig J;Cromer CL;Dowell ML;Jimenez R;Hoover AS;Silverman KL;Ullom JN
我们描述了一种用于超快x射线吸收光谱的激光驱动x射线等离子体源。该源由1 kHz、20 W的飞秒脉冲红外激光器和水靶组成。我们提出的X射线光谱作为激光能量和脉冲持续时间的函数。此外，我们调查等离子体温度和光子通量，因为我们改变激光能量。我们通过使用多毛细管光学器件聚焦产生的X射线，获得了75 μm FWHM X射线斑点尺寸，包含106个光子/s。由于X射线吸收光谱的获取需要对来自>107个激光脉冲的测量进行平均，因此我们还提供了关于源稳定性的数据，包括X射线产额和X射线光谱形状的单脉冲测量。在单脉冲测量中，X射线通量的测量标准偏差为8%，其中激光指向是可变性的主要原因。此外，我们表明，从单脉冲的X射线光谱形状的变化是低的，从而证明从不同的激光脉冲到一个单一的光谱中获得的X射线的组合。最后，我们显示了一个静态的草酸铁溶液的X-射线吸收光谱检测的微量热计阵列。总之，我们的研究结果表明，这种基于水射流的等离子体源是一个合适的候选人，基于实验室的时间分辨X射线吸收光谱实验。
We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.