Development of a hybrid helical microwiggler with four poles per period

A compact strong test hybrid helical microwiggler has been designed and developed with ten periods, each with length 10 mm and four poles, and gap diameter of 5 mm. One period is constructed with four segments. Each segment has a thickness of 2.5 mm and consists of pentagonal permanent magnets and permendur poles. Each segment is stacked along the wiggler axis and is rotated by an angle of 90(degree) to the adjacent segment. The outer width is only 72 mm. The wiggler is divided into two sections where two kinds of permanent magnet - one with apex angle of 90(degree) and one with 120(degree) - were installed in order to find out the effect of geometrical size for the field. Peak fields of 0.360 and 0.381 T were achieved with small rms variations of about 1.1% and 0.6%, respectively, depending on the geometrical size of the permanent magnet.