The development of superconducting magnet technology for tokamak magnets:R&D update and plan

A tokamak/fusion reactor is device, which initiates, confines and shapes the plasma using magnetic coils in a vacuum vessel, which isolates it from the outer environment. The toroidal field coils of tokamak generates steady magnetic field in toroidal direction to confine the plasma. The central solenoid of this device acts as primary, in which, the change in current induces a toroidal electric field required to initiate the plasma as secondary in the vacuum vessel. The poloidal field coils are used to shape the plasma. Presently, IPR is working with low temperature superconducting (LTS), NbTi based SST-1 tokamak. R&D activity has also been initiated for the development of high temperature superconductor (HTS) based conductor and coils for future fusion reactor, as the conventional LTS (Nb₃Sn and NbTi) cannot be used at higher magnetic field (>13 Tesla) due to their upper critical field limitations. The development of large volume superconducting coils for magnetic confinement of plasma was initiated long back at IPR for SST-1 tokamak with custom made NbTi Cable in Conduit Conductor (CICC) superconductor (SC). The TF coils of SST-1 operated up to 2.7 T, at the major radius of 1.1 m of the SST-1. The in-house conductor development technologies, right from SC strands to high current NbTi and Nb₃Sn CICC have been established afterwards for future tokamaks. The installation and performance testing of large volume cryostat, which can house large SC coil of cross-sectional area about 20 m2 for low temperature testing has also been completed. The significant progress has been made for the development of high temperature superconductor (HTS) based 1 kA cable, Nano-ohm class HTS-HTS tape joints , Nb₃Sn-NbTi CICC hybrid joints, Nb₃Sn coil, quench dynamics study in 2nd generation HTS tapes, sub-cooed LN2 system and 1.1 T compact HTS solenoid coil. The in-house development of intermediate temperature mono-filament MgB₂ wire, high current HTS cable and shaped coils are in progress. The detailed R&D programme encompassing the fabrication of LTS, HTS conductor, coils, test facility and the test results of conductors and coils along with the future plans will be elaborated in this presentation. (author)