A Short-Period High-Field Undulator Study

With the intention to develop a technology suitable for a 2.4 m magnetic length, superconducting undulator with 0.8 T on the beam and a 15 mm period for the IXS beam line at the Advanced Photon Source at the Argonne National Lab, USA, a 0.6-m Nb₃Sn undulator demonstration magnet is under development at the NHMFL. The intent is to investigate the applicability of Nb₃Sn superconductor, in combination with soft magnetic materials, for a 15 mm period planar superconducting undulator. The demonstration requirements include a peak undulator magnetic field of at least 0.8 T and a vertical stay-clear aperture for the beam of at least 7 mm. In concept, the beam tube will be thermally isolated from the windings and operated at LN₂ temperature to promote system reliability. Liquid helium and nitrogen reservoirs provide conduction cooling and the former also acts as a basic structural element. A brief description of a design is presented. A comparative study of fully and partly iron yokes and their effect on the required current density is performed. The results have implications for the yoke assembly procedure. Finally, a new yoke-winding geometry is presented