Trapezoidal Wire for the Hollow Superconducting Cable Designed for Fast Cycling Synchrotron Magnets

A new hollow high current cable was designed at JINR for the magnets of the GSI accelerator ring SIS 100. To increase both the structural current density and the operating current it was proposed to replace the superconducting wires with a round cross section (0.5 mm in diameter) by wires having a keystoned or trapezoidal (in the first approximation) cross section.Trapezoidal fine filament superconducting wire based on NbTi alloy, intended for operating at fields having sweep rate from 1 up to 4 T/s, has been developed and manufactured by Bochvar Institute (VNIINM). The wire with 10374 filaments and Cu/non Cu of 1.8 was fabricated by a single stacking method. Each filament was surrounded by a matrix of commercial MN‐5 alloy (Cu‐5wt.%Ni). The trapezoidal shape was formed by two steps drawing of a round 1.01 mm wire at a final stage of production. The optimized cross section is 0.73 × 1.08 mm at the medium line.The critical current density is more than 2700 A/mm2 at 5 T, 4.2 K. The current carrying capacity...