Effects of a hybrid superconducting three-pole wiggler on the stored beam at the SAGA-LS storage ring

Practical effects of a hybrid three-pole wiggler on the beam was investigated at 1.4 GeV storage ring of Saga light source in the viewpoint of evaluation of the applicability of the wiggler on actual storage ring. The wiggler was developed to generate hard X-rays up to 40 keV approximately. The magnet system consisted of three isolated poles—a superconducting main pole and two normal-conducting side poles. To suppress the increase in the second magnetic field integral caused by the isolated pole structure, thick field clamps that generate a negative field for the main pole were located at both ends of the main pole. This isolated pole structure with field clamps generated an unusual field distribution. The practical effects of the wiggler field on the storage ring (e.g., the focusing force, the sextupole strength, radiation power and the beam emittance ) were investigated by performing measurements. The results agreed roughly with practical field calculation model, which was corrected by result of the magnetic field measurement. Practical multipole effects were relatively tolerable or controllable. In addition, the employment of the field clamps and the normal-conducting side pole, which contributed to the decrease of peak field of the side poles, brought about reduction of beam effects due to curvature distribution at the side poles.