The magnetic and diagnostics systems for the Advanced Photon Source self-amplified spontaneously emitting FEL

A self-amplified spontaneously emitting (SASE) free-electron laser (FEL) fo r the visible-to-ultraviolet spectral range is under construction at the Ad vanced Photon Source at Argonne National Laboratory. The amplifier part of the FEL consists of twelve identical 2.7-m-long sections. Each section incl udes a 2.4-m-long, 33-mm-period hybrid undulator, a quadrupole lens, and a set of electron beam and radiation diagnostics equipment. The undulators wi ll operate at a fixed magnetic gap (approx. 9.3 mm) with K = 3.1. The elect ron beam position will be monitored using capacitive beam position monitors , YAG scintillators with imaging optics, and secondary emission detectors. The spatial distribution of the photon beam will be monitored by position s ensitive detectors equipped with narrow-band tilters. A high-resolution spe ctrograph will be used to observe the spectral distribution of the FEL radi ation. (C) 1999 Elsevier Science B.V. All rights reserved.