Slices and Ellipse Geometry

We discuss the new problems emerging in charged beam transport for SASE FEL dynamics. The optimization of the magnetic transport system for future devices requires new concepts associated with the slice emittance and the slice phase space distribution. We study the problem of electron beam slice matching and guiding in transport devices for SASE FEL emission discussing matching criteria and how the associated design of the electron transport line may affect the FEL output performances. We analyze different matching strategies by studying the relevant effect on the FEL output characteristics.