Development of the strong electromagnet wiggler

A description is given of the design approach used for a permanent magnet-assisted electromagnet under development as part of the Induction Linac Free-Electron-Laser program. A single-period schematic of the wiggler is described. This device is an iron-core, DC electromagnet in which poles of identical magnetic scalar potential are attached to large iron plates. These scalar potential busses are bridged by iron plates around which the large primary coils are wound. Smaller trim coils that provide the magnetic-field taper are placed at the base of the poles. Permanent-magnet material, magnetized in a direction opposite to that of the field created by coils, is placed between the poles. The magnetic scalar potential of the poles can be elevated to the desired point while delaying the onset of magnetic saturation in the iron. Data are presented from a seven-period prototype wiggler that has been designed, fabricated and tested.