Polarization control in an X-ray free-electron laser
Polarization control in an X-ray free-electron laser
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DOI：
10.1038/nphoton.2016.79
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发表时间：
2016-07-01
期刊：
影响因子：
35
通讯作者：
Nuhn, Heinz-Dieter
中科院分区：
文献类型：
--
作者：
Lutman, Alberto A.;MacArthur, James P.;Nuhn, Heinz-Dieter
X射线自由电子激光器是一种独特的高亮度相干辐射源。然而，现有的设备只提供线偏振光，排除了手性动力学的研究。一个被称为Delta波荡器的设备已经安装在直线加速器相干光源（LCLS）上，以提供可调谐的偏振。利用反向锥形平面波荡器线预聚束和束转向的新技术，在500- 1，200 eV处产生数百微焦耳的圆偏振X射线脉冲。这些X射线脉冲是几十飞秒长，在707 eV处具有0.98（+0.02）（-0.04）的圆偏振度，并且可以在能量上被扫描。我们还提出了一种新的双色X射线泵浦X射线探头的LCLS工作模式。支持Δ E/E = 2.4%的能量差，并且第二脉冲可以被调整到任何椭圆偏振。在这种模式下，可以修改两个脉冲的指向、定时、强度和波长。
X-ray free-electron lasers are unique sources of high-brightness coherent radiation. However, existing devices supply only linearly polarized light, precluding studies of chiral dynamics. A device called the Delta undulator has been installed at the Linac Coherent Light Source (LCLS) to provide tunable polarization. With a reverse tapered planar undulator line to pre-microbunch the beam and the novel technique of beam diverting, hundreds of microjoules of circularly polarized X-ray pulses are produced at 500-1,200 eV. These X-ray pulses are tens of femtoseconds long, have a degree of circular polarization of 0.98(+0.02)(-0.04) at 707 eV and may be scanned in energy. We also present a new two-colour X-ray pump-X-ray probe operating mode for the LCLS. Energy differences of Delta E/E = 2.4% are supported, and the second pulse can be adjusted to any elliptical polarization. In this mode, the pointing, timing, intensity and wavelength of the two pulses can be modified.