Speaker
Description
Next-step US spherical tokamak test facilities and/or compact stellarators configured as fusion pilot plants (FPP) to support fusion commercialization are recommended options by multiple recent consensus studies. The goal for a FPP is to make 50-100 MW net electricity power plants with either extended long pulses or steady state options. Significant HTS conductor and coil technology efforts are underway by privately funded startups with the goal to demonstrate HTS maturity for commercial fusion. Test results, however, indicate critical issues remain to meet performance goals, and demonstrate coil operation repeatability and reliability. To this end, exploring and enabling multiple viable conductors is critical for enabling next generation fusion magnets beyond ITER with advances in conductor materials, coil manufacturing, and HTS quench sensing. To validate the low AC loss characteristics of commercial Bi-2212 conductors made in the USA, a simpler ohmic heating (OH) coil module is developed for next step compact tokamak devices.
The primary goal for this project is to build and test a Bi-2212 prototype coil designed by Princeton Plasma Physics Laboratory (PPPL) aiming for a spherical tokamak (ST) ohmic heating central solenoid (CS) fast ramp operation. For a ST pilot plant, one of the superconducting magnet challenges is the tight space constraint in a center column where the in-board toroidal field (TF) coil bundle and the OH coil are assembled inside a center cryostat and a structural casing where plasma facing components are attached. To this end, a model coil design based on high current density Rutherford cables consisting of 17 strand Bi-2212 wires previously used and tested in HEP was developed for ST fusion. Recent evaluations of Bi-2212 wires have shown that Bi-2212 conductors have orders of magnitude lower AC losses compared to REBCO coated conductors, very comparable to ITER Nb3Sn wires. This makes Bi-2212 wires suitable and potentially the only viable high field option for a fast ramp, high field solenoid for compact ST operation. This is significant because most recent studies in support of private fusion have shown promising results of net fusion gain by operating a pulsed tokamak machine.
