Development of a 7 tesla superconducting wiggler

A 7 T three poles superconducting wiggler has been constructed to be used as a light source in AURORA-2D, a 700 MeV compact SR ring. The wiggler is cooled by compact Gifford-McMahon cryocoolers without liquid helium. The main components of the wiggler are three pairs of racetrack superconducting coils in an iron yoke, bismuth based oxide superconducting current lead unit and Gifford-McMahon cryocoolers. The coils generate a magnetic field of 7 T in a 40 mm coil gap within 360 seconds. The magnetic field period along the electron beam of the SR ring is 342 mm. The magnetic field integral is less than 4/spl times/10/sup -4/ Tm. The coils and the yoke are cooled by a Gifford-McMahon cryocooler with Joule-Thomson valve. The current lead unit and the thermal shield plate are cooled by separate Gifford-McMahon cryocoolers without Joule-Thomson valves. The current lead unit is designed to be easily removed for maintenance. The performance test in AURORA-2D was successfully completed. The maximum beam current was 19 mA at 700 MeV.