Ha. Leupold et al., AXIALLY POLARIZED WIGGLER RADIATION FROM A TOROIDAL ELECTRON-BEAM SOURCE, IEEE transactions on magnetics, 34(4), 1998, pp. 1405-1407
Recent work has described wigglers in which the radiating electron bea
m circulates azimuthally within a toroidal tube where a surrounding pe
rmanent magnet structure keeps the beam on a mean circular path and si
multaneously provides the field periodicity for wiggler action.(1,2) B
oth the mean field and the periodic one are in the axial direction so
that the resulting synchrotron and wiggler radiations are both polariz
ed in the principal toroidal plane, The present work analyzes a struct
ure in which the synchrotron and wiggler polarizations are mutually or
thogonal so that one or the other can be easily eliminated to provide
essentially monochromatic radiation. This is accomplished by an azimut
hally periodic arrangement of magic ring sections that form a toroidal
tube. These are oriented with their axial field components constant a
nd equal and their radial components equal but alternating radially ou
tward and inward in direction. The constant axial field holds the elec
tron beam in a circular path while the alternating radial field provid
es the wiggler action. The wiggler radiation has n times the frequency
of the synchrotron radiation where n is the number of azimuthal perio
ds per circuit.