Investigation of 15 to 24 MW Resistive Insert Magnets Built Into a 20 T $var\noth\ing$ 440 mm Room-Temperature Bore Superconducting Outsert Magnet

The Tsukuba Magnet Laboratory and the High Field Laboratory for Superconducting Materials collaborated on developing the next-generation 50 T-class hybrid magnet. One of the properties to be incorporated into this next-generation hybrid magnet is energy-saving operation in generating a high-strength magnetic field. This report presents the estimated performance of this hybrid magnet, on the basis of a 20 T Ø440 mm room temperature bore for the superconducting outsert magnet, DC power of 15-24 MW for a three-layered Bitter resistive insert magnet, and a Ø32 mm room-temperature bore for the resistive insert magnet. Cu-Zr (Cu-Ag) alloy is assumed material to be used for the outermost layer (inner two layers) of the Bitter magnet. The estimation indicates that the hybrid magnet generates magnetic fields beyond 47.9 T (49.1 T) for a resistive insert magnet operation power of 15 MW (24 MW) in a 20 T background magnetic field, where the upper-limit design stress on the innermost Bitter coils is tentatively assumed to be 800 MPa. An ultimate tensile strength exceeding 1140 MPa with a conductivity of 72% International Annealed Copper Standard (IACS) for a Cu-Ag alloy plate would be necessary to meet the design stress of 800 MPa. Using this material, we could make the 15 MW water-cooled resistive insert magnet (WM) for this energy-saving, compact hybrid magnet that generates magnetic fields of 47 T and beyond. For a moderated upper-limit design stress of 760 MPa, the corresponding magnetic fields of the hybrid magnet are 47.5 and 48.5 T.