DEVELOPMENT OF A FOCUSING WIGGLER MAGNET WITH PARABOLIC POLE FACES

A focusing wiggler magnet which consists of permanent magnets with par abolic pole faces has been developed. A magnet with parabolic pole fac es gives an additional sextupole contribution to the conventional wigg ler field, and generates a focusing force in both directions on an ele ctron beam. Furthermore, it can give the FEL resonance properties as w ell as a helical wiggler. The shape of the magnet pole faces has been optimized using the TOSCA code. The alloy Nd-Fe-B was chosen as the ma gnetic material for a peak field of more than 0.43 T with a gap of 23 mm on the wiggler axis. Magnetic field errors could be substantially r educed using thin iron shimming plates attached to the permanent magne ts. The results of the magnetic field measurements are in good agreeme nt with the values obtained by TOSCA. Numerical simulation of the elec tron trajectory using a measured magnetic field is performed and it ve rified that the wiggler with parabolic pole faces has enough focusing force in the x direction in addition to the y direction.