van Rens J F M, Verhoeven W, Franssen J G H, Lassise A C, Stragier X F D, Kieft E R, Mutsaers P H A, Luiten O J
Department of Applied Physics, Coherence and Quantum Technology Group, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
Department of Applied Physics, Coherence and Quantum Technology Group, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
Ultramicroscopy. 2018 Jan;184(Pt B):77-89. doi: 10.1016/j.ultramic.2017.10.004. Epub 2017 Oct 12.
We present a theoretical description of resonant radiofrequency (RF) deflecting cavities in TM mode as dynamic optical elements for ultrafast electron microscopy. We first derive the optical transfer matrix of an ideal pillbox cavity and use a Courant-Snyder formalism to calculate the 6D phase space propagation of a Gaussian electron distribution through the cavity. We derive closed, analytic expressions for the increase in transverse emittance and energy spread of the electron distribution. We demonstrate that for the special case of a beam focused in the center of the cavity, the low emittance and low energy spread of a high quality beam can be maintained, which allows high-repetition rate, ultrafast electron microscopy with 100 fs temporal resolution combined with the atomic resolution of a high-end TEM. This is confirmed by charged particle tracking simulations using a realistic cavity geometry, including fringe fields at the cavity entrance and exit apertures.
我们提出了一种关于TM模式下共振射频（RF）偏转腔的理论描述，该腔作为超快电子显微镜的动态光学元件。我们首先推导了理想药盒形腔的光学传递矩阵，并使用柯朗 - 西奈形式来计算高斯电子分布通过该腔的六维相空间传播。我们推导了电子分布横向发射度和能量展宽增加的封闭解析表达式。我们证明，对于聚焦在腔中心的光束的特殊情况，可以保持高质量光束的低发射度和低能量展宽，这使得能够实现具有100 fs时间分辨率的高重复率超快电子显微镜，同时具备高端透射电子显微镜的原子分辨率。使用包括腔入口和出口孔径处边缘场的实际腔几何结构进行的带电粒子跟踪模拟证实了这一点。
