ANALYSIS OF THE SUPERCONDUCTING WIGGLER MAGNETS FOR THE ATF HARMONIC-GENERATION FEL EXPERIMENT

In this paper, we consider the superconducting wiggler magnet under co nstruction for the High Gain Harmonic Generation experiment (HGHG) at the Accelerator Test Facility (ATF) at BNL. This wiggler consists of a n energy modulation section, a dispersion magnet and a radiator sectio n. We present an analysis of the dispersion magnet and of the end effe cts in the other wiggler sections. The purpose of the dispersion magne t is to convert energy modulation of the electron beam into spatial bu nching. For the dispersion magnet, we discuss the physical requirement s, analyze the magnetic design, determine the focussing properties, an d consider the effect of departures from ideal behavior on the FEL gai n. In the modulator and radiator wigglers we analyze the effects due t o the ends of the wiggler and discuss their correction. In addition, t he localized field produced by a trim coil for horizontal beam steerin g is investigated.