End effects of a bifilar magnetic wiggler

J. Fajans
1984 Journal of Applied Physics  
The magnetic field at the entrance of a wiggler magnet in a Free Electron Laser (FIl,) determines the character of the electron orbits and influences the FEL gain. To obtain the desired adiabatic entrance conditions, it is necessary to investigate different methods of connecting leads to the wiggler as well as methods of gradually reducing the wiggler field. The field of a current driven, finite length bifilar helical wiggler magnet is derived and is used to investigate the magnetic field end
more » ... rturbations. For a limited range of wiggler parameters, flaring the wiggler end produces an adiabatic entrance region. Alternately, gradually terminating the wiggler current at the wiggler entrance is shown to produce an adiabatic entrance for a larger range of parameters.
doi:10.1063/1.332846 fatcat:xu2arjkp3rgjbc5jvnr3fjqriu