Development of an electromagnetic helical microwiggler with permanent magnets

An electromagnetic helical microwiggler with three poles per period, employing permanent magnets to suppress leakage flux in the vicinity of the gap, has been developed. The wiggler is embedded in a double-walled vacuum chamber with a water jacket for heat removal. The field profile consists of a 30-period-long uniform-field section terminated at both ends with 5-period-long tapered fields. A peak on-axis field of 3.0 kG was achieved with a period of 7.9 mm and a gap diameter of 4.6 mm. An optimal sorting technique was applied to the permanent magnets to minimize variations in the peak field amplitude. Based on measurements of the test wiggler, rms amplitude variations of 1.4% and 2.6% in, respectively, the horizontal and vertical field amplitudes were attained.