Two-stage FEL (Free Electron Laser) program

A review of a two-stage free electron laser research program is presented. The work includes cavity and wiggler magnet design, a study of methods for minimizing electron energy spread at high first stage intensity, and calculations of second stage gain. A quasioptical cavity is proposed to contain the first-stage long-wavelength radiation while permitting transmission of second-stage short-wavelength radiation. A permanent magnet helical wiggler will be used to produce the long-wavelength radiation. At high first stage intensities (approx. 10 to the 8th power W sq cm) the energy spread produced in the wiggler will be > 10%. For the experiment being proposed the beam line and electron collector must be modified to accept this spread. Companion papers in this volume give additional details of the cavity design and minimization of energy spread.