R&D Of Liquid Helium Inner Cooling Superconducting Cable For Hiaf Fast-pulsed Magnet

Fast-pulsed superconducting magnet will be used in HIAF(High Intensity heavy ion Accelerator Facility), which is a large research infrastructure proposed by IMP(Institute of Modern Physics). BRing is the booster of this facility for speeding particles. For the superconducting magnets of BRing will be operated at fast-pulsed cycled mode, it must employ cable to wind the coils so that the coil turns can be reduced and the inductance can be decreased. By comparing the behaviors of several superconducting cables, the liquid helium inner cooling superconducting cable is selected for the HIAF fast-pulsed magnets. R&D of the cable is the foundation of the HIAF fast-pulsed magnets because its performance directly determines the magnets’ behavior.The liquid helium inner cooling superconducting cable consists of dozens of superconducting strands wrapped around a Cu-Ni tube. A thin nichrome wire is spirally wound with strain around the strands for fixing. Kapton tapes and fiberglass tapes are wrapped at the outermost layer for insulation. Cooling by forced flow liquid helium, less liquid helium is required compared with bath cooling. When the cable is subjected to the changes of the magnetic field or operating current, the AC losses will be dissipated. The formulas for losses calculation are derived through theoretical analysis. The superconducting wire is the substance for current carrying, so its performance largely dictates the cable’s behavior. In order to attain higher critical current and lower AC losses, we have developed three kinds of superconducting wires. After comparing their critical currents and AC losses by test, the best one will be chosen. The study of the cable operating stability is another important content in this paper. We obtain the maximum currents below which the cable is stable at any operating condition according to different stabilization theories. The stability margin of the HIAF cable is computed with THEA code and the quench behavior of the cable is also simulated.A 200 meters liquid helium inner cooling superconducting cable has been successfully fabricated in China for the first time. Technical details of the cable fabrication are presented in this paper and the specifications of each procedure are also given. Both critical current and hysteresis loss of the wire have been studied. The critical current of the wire has reached the design goal while the loss is higher than the calculated. The critical current of the cable is also measured by a simple test machine developed at IMP. The test results indicate that the cable satisfies the operation requirement with an exciting current up to 15 k A at the magnetic field of 3 T.