Some aspects of cable design for fast cycling superconducting synchrotron magnets

The world's experience in application and manufacturing of superconducting cables for fast cycling synchrotrons (operating frequency f = 1 Hz) is limited up to now to a hollow multifilament NbTi cable cooled with two-phase helium flow. The cable of 7 mm in diameter has critical current of 8400 A at B = 2.5 T and dB/dt = 4 T/s. The degradation of critical current does not exceed 10% up to dB/dt = 8 T/s. The cable was designed and has been used for the magnets of the Nuclotron superconducting synchrotron at JINR in Dubna. The recent R&D was motivated by the new project of a superconducting synchrotron SIS100 at GSI in Darmstadt. Besides the basic option, i.e., the present Nuclotron-type cable, other design options are proposed. Their suitability for application in the conditions specified for the SIS 100 are considered. The improved characteristics of the Nuclotron-type cable and the magnet coil parameters are also presented.