We propose a new filter method to generate electron beams of high polarization from bubble and blow-out wakefield accelerators. The mechanism is based on the idea to identify all electron-beam subsets with low-polarization and to filter them out by an X-shaped slit placed right behind the plasma accelerator. To find these subsets we investigate the dependence between the initial azimuthal angle and the spin of single electrons during the trapping process. This dependence shows that transverse electron spins preserve their orientation during injection if they are initially aligned parallel or anti-parallel to the local magnetic field. We derive a precise correlation of the local beam polarization as a function of the coordinate and the electron phase angle. Three-dimensional particle-in-cell simulations, incorporating classical spin dynamics, show that the beam polarization can be increased from 35 injected beam flux, which can be strongly restricted in pursuit of high polarization, is no longer limited in our approach. This idea marks an efficient and simple strategy to generate energetic polarized electron beams based on wakefield acceleration.

中文翻译：

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自旋滤波器，用于等离子体尾波场中的极化电子加速

我们提出了一种新的滤波方法，可以从气泡和吹出的尾波场加速器产生高极化电子束。该机制基于这样的想法：识别所有具有低极化的电子束子集，并通过位于等离子加速器正后方的X形缝隙将其过滤掉。为了找到这些子集，我们研究了在捕获过程中初始方位角与单个电子的自旋之间的依赖性。这种依赖性表明，如果横向电子自旋最初与局部磁场平行或反平行排列，则在注入过程中将保持其方向。我们得出了局部束极化与坐标和电子相角的函数的精确相关关系。包含经典自旋动力学的三维单元粒子模拟，结果表明，可以从35个注入束通量中增加束偏振，这在追求高偏振时可以受到严格限制，在我们的方法中不再受到限制。这个想法标志着一种基于尾场加速度产生高能极化电子束的有效而简单的策略。