The design of a compact cryogen-free superconducting wavelength shifter for synchrotron radiation

A compact three-pole superconducting magnet with a warm bore for electron orbit has been designed to serve as a wavelength shifter for Taiwan synchrotron radiation light sources. The wavelength shifter will have a warm beam duct, which is 600 mm in length, 100 mm in width and 20 mm in high. Three pairs of racetrack superconducting coils were designed to create a central field and to adjust the integral field close to zero. A maximum magnetic field of 6.5 Tesla at the central pole will be generated. To avoid induced currents, all six coils are connected electrically in series and powered by a high current power supply. Two low current trim power supplies are used to adjust currents on the two side pairs of coils in order to eliminate the first and the second magnetic field integrals. The shape of pole pieces and superconducting coils are specially designed to minimize the higher harmonic terms of the magnetic field, especially the sextupole field component. Both the superconducting coils and the iron yokes are cooled by a single 1.5 W Gifford-McMahon cryo-cooler. The normal operation of the 6.5 T wavelength shifter will be cryogen free.