Novel schemes for generating ultralow emittance electron beams have been developed in past years and promise compact particle sources with excellent beam quality suitable for future high-energy physics experiments and free-electron lasers. Current methods for the characterization of low emittance electron beams such as pepperpot measurements or beam focus scanning are limited in their capability to resolve emittances in the sub 0.1 mm mrad regime. Here we propose a novel, highly sensitive method for the single shot characterization of the beam waist and emittance using interfering laser beams. In this scheme, two laser pulses are focused under an angle creating a gratinglike interference pattern. When the electron beam interacts with the structured laser field, the phase space of the electron beam becomes modulated by the laser ponderomotive force and results in a modulated beam profile after further electron beam phase advance, which allows for the characterization of ultralow emittance beams. 2D PIC simulations show the effectiveness of the technique for normalized emittances in the range of ${\epsilon }_n=[0.01,1]\mathrm{mm}\mathrm{mrad}$.

中文翻译：

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利用结构化光场表征超低发射电子束

过去几年中已经开发出了产生超低发射电子束的新方案，这些方案有望提供具有优异束质量的紧凑粒子源，适用于未来的高能物理实验和自由电子激光器。当前用于表征低发射率电子束的方法（例如胡椒锅测量或束聚焦扫描）在分辨小于0.1 mm mrad范围内的发射率方面能力有限。在这里，我们提出了一种新颖的，高度灵敏的方法，用于使用干涉激光束来表征束腰和发射度。在该方案中，两个激光脉冲以一定角度聚焦，从而形成光栅状干涉图样。当电子束与结构化激光场相互作用时，电子束的相空间在激光质动力作用下被调制，并在进一步推进电子束相位之后产生调制的束轮廓，从而可以表征超低发射束。二维PIC模拟显示了该技术在200-600 nm范围内对归一化发射率的有效性${\epsilon }_{ñ}=[0.01，\mathrm{1个}]\mathrm{毫米}\mathrm{姆拉德}$。