Quantitative agreement between dynamical rocking curves in ultrafast electron diffraction for x-ray lasers
Quantitative agreement between dynamical rocking curves in ultrafast electron diffraction for x-ray lasers
复制标题
DOI：
10.1016/j.ultramic.2021.113211
复制
发表时间：
2021-02-11
期刊：
影响因子：
2.2
通讯作者：
Weathersby, S.
中科院分区：
文献类型：
--
作者：
Malin, L. E.;Graves, W. S.;Weathersby, S.
通过薄图案化硅膜的电子衍射可用于在电子分布中产生复杂的空间调制。通过精确地改变诸如晶体取向和晶片厚度等参数，可以控制衍射平面中的反射强度，并且通过放置孔径来阻挡除了一个点之外的所有点，我们可以用图案化膜的不同部分形成图像，就像显微镜中的明场成像一样。然后，图案化的电子束可以用于控制随后的X射线发射的相位和幅度，从而实现新颖的相干X射线方法。电子本身也可以用于飞秒时间分辨衍射和显微镜。作为图案化光束的第一步，我们通过实验和模拟证明了准确预测和控制衍射光斑强度的能力。我们模拟MeV的透射电子衍射图案使用多层面方法的各种结晶取向的单晶Si（001）膜附近的正常束。由此产生的布拉格反射的强度图进行比较，在SLAC的加速器结构测试区超快电子衍射（ASTA UED）设施获得的实验结果。此外，初始电荷的非弹性和弹性散射的分数与膜的吸收一起被估计沿着，以确定在Si（001）膜的图案化版本中将看到的对比度。
Electron diffraction through a thin patterned silicon membrane can be used to create complex spatial modulations in electron distributions. By precisely varying parameters such as crystallographic orientation and wafer thickness, the intensity of reflections in the diffraction plane can be controlled and by placing an aperture to block all but one spot, we can form an image with different parts of the patterned membrane, as is done for bright-field imaging in microscopy. The patterned electron beams can then be used to control phase and amplitude of subsequent x-ray emission, enabling novel coherent x-ray methods. The electrons themselves can also be used for femtosecond time resolved diffraction and microscopy. As a first step toward patterned beams, we demonstrate experimentally and through simulation the ability to accurately predict and control diffraction spot intensities. We simulate MeV transmission electron diffraction patterns using the multislice method for various crystallographic orientations of a single crystal Si(001) membrane near beam normal. The resulting intensity maps of the Bragg reflections are compared to experimental results obtained at the Accelerator Structure Test Area Ultrafast Electron Diffraction (ASTA UED) facility at SLAC. Furthermore, the fraction of inelastic and elastic scattering of the initial charge is estimated along with the absorption of the membrane to determine the contrast that would be seen in a patterned version of the Si(001) membrane.