FIELD DESIGN STUDIES OF A PLANAR HYBRID PERMANENT MAGNET UNDULATOR WITH STRONG PLANAR PERMANENT-MAGNET FOCUSING/

Undulators for Free Electron Laser (FEL) amplifiers driven by multi-Ge V electron beams generally require superimposed focusing substantially stronger than that provided by their natural focusing fields. In rece nt years a wide variety of focusing schemes and configurations have be en proposed for undulators of this class, ranging from conventional cu rrent-driven quadrupoles external to the undulator magnets to permanen t magnet (PM) lattices inserted into, or adjacent to, the insertion de vice gap. In this paper we present design studies of the field structu re of a flexible hybrid/PM undulator with superimposed planar PM focus ing proposed for a 1.5 Angstrom Linac Coherent Light Source (LCLS) und ulator driven by an electron beam with a 1 mm mrad normalized emittanc e. Attainable field parameters, tuning modes, and trajectory performan ce of the proposed structure are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.