Optics of beam recirculation in the CEBAF CW linac

The use of recirculation in linear accelerator designs requires beam transport systems that will not degrade beam quality. A design for the transport lines to be used during recirculation in the CEBAF accelerator is presented. These beam lines are designed to avoid beam degradation through synchrotron radiation excitation or betatron motion mismatch, are insensitive to errors commonly encountered during beam transport, and are optimized for electron beams with energies of 0.5 to 6.0 GeV. Optically, they are linearly isochronous second order achromats based on a missing magnet FODO structure. Lattice specifications and results of analytic estimates and numerical simulations of the performance of the beam transport system are given