Rapidly-cycling superconducting accelerator magnets for fair at GSI

The demand for high beam intensities leads to the requirement of rapidly-cycling magnets for synchrotrons. An example is FAIR (Facility for Antiproton and Ion Research) at GSI, which will consist of two superconducting synchrotrons (SIS 100 and SIS300) in one tunnel and several storage rings. The high field ramp rate (up to 4 T/s) and the repetition frequency of up to 1 Hz require R&D for the superconducting magnets of these rings. Persistent currents in the superconductor and eddy currents in wire, cable, iron and vacuum chamber reduce the field quality and generate AC losses at cryogenic temperatures. A magnet lifetime of 20 years is desired, resulting in up to 2ldr10⁸ magnet cycles. Therefore, special attention has to be paid to magnet material fatigue problems. R&D work is being done, in collaboration with many institutions. Model dipoles were built and tested. The results of the R&D are reported. Full length dipoles for SIS 100 are under construction.