Self-amplified spontaneous emission (SASE) free electron laser (FEL) devices have disclosed an unexpected interplay between the laser intensity growth and regions of the electron bunch of the order of the coherence length. They are usually identified with the bunch slice and contribute to the laser dynamics with their own characteristics. The dynamical effects inducing geometrical and phase space misalignment of bunch slice in X-ray operating FELs can be traced back to a plethora of phenomena, both in the Linac accelerating section or inside the beam transport optic magnet. They are responsible for spoiling of the beam projected qualities and, if not corrected properly, induce an increase of the saturation length and a decreasing of the output power. We discuss the inclusion of these effects in models employing scaling formulae.

中文翻译：

---

切片集体动力学、预计发射率恶化和自由电子激光性能的不利影响

自放大自发发射 (SASE) 自由电子激光 (FEL) 器件揭示了激光强度增长与相干长度数量级的电子束区域之间的意外相互作用。它们通常被识别为束切片，并以其自身的特性为激光动力学做出贡献。在 X 射线操作的 FEL 中引起束切片的几何和相空间错位的动力学效应可以追溯到直线加速器加速部分或光束传输光学磁体内部的大量现象。它们负责破坏光束投影质量，如果没有正确校正，则会导致饱和长度增加和输出功率降低。我们讨论了在使用缩放公式的模型中包含这些影响。