Orbits and fields in the helical wiggler

The ''helical wiggler'' is a device in which relativistic electrons pass through a transverse magnetic field whose direction revolves with distance along the beam axis. In this paper we discuss the electron orbits in this device. The field patterns and necessary current distributions are established. Finally, the question is treated as to whether this device can be incorporated into a storage ring without destroying the circulating beam. It is concluded that there is reason to expect satisfactory performance from helical wigglers in storage rings