Blocks-in-Conduit: REBCO Cable for a 20T@20K Toroid for Compact Fusion Tokamaks

Abstract

Blocks-in-Conduit is a novel approach to cable, coil, and splice technologies with unique benefits for a high-current-density toroid D winding to operate at 20 T, 20 K. Blocks of REBCO tape are cabled in conduit, with a thin-wall center-tube spring that provides transposition, stress management at the cable level, and cross-flow cooling of a thick-coil toroid winding. The coil technology utilizes a co-wound armor structure that integrates stress management and cross-flow cooling and bypasses coil stress to protect the BIC. An interleaved splice joint enables low-resistance demountable splices of the windings. These provisions yield maximum current density in the winding pack, maximum stability of the REBCO tape blocks, and minimum conductor cost for a tokamak toroid.

Experimental study of stability, quench propagation and detection methods on 15 kA sub-scale HTS fusion conductors in SULTAN

“…This is clearly seen for the operation at 9 kA for voltages above 0.2 V. This discrepancy should be primarily caused by the QPV, which is assumed to be constant in the assessment, whereas it decreases substantially in the SULTAN measurements once the propagating front exits the HFZ of ∼0.5 m length (see related discussion in [39]). Note that the measured voltage at higher currents has an offset at zero time corresponding to the contribution from the resistive zone that reached the peak temperature of ∼40 K, which is not included in equation (6).…”

“…The operating current has a strong impact on the measured curves, resulting in a counterintuitive trend of the maximum temperature decrease with the increasing current for a given value of the total voltage. However, it can be understood from the terms comprising equation (6), which actually indicates at the maximum temperature being inversely proportional to the quench integral, i.e. T max ∼ V/ ( I 2 t ) .…”

“…Recent advances in the technology of high-temperature superconductors (HTS), such as an increased critical current density and higher production yield, have finally turned the possibility for HTS-based fusion magnets into a practical matter. From a variety of high-current HTS conductor designs proposed for fusion magnets, relevant demonstrations have already been performed on certain twisted stacked-tape concepts [1,2], while other twisted stacked-tape variants [3][4][5][6] as well as conductor on round core (CORC) conductors [7] are yet to be tested. Simplified concepts based on a straight stack of tapes are also considered for coil windings operated in stationary mode [8][9][10].…”

Winding angle optimization and testing of small-scale, non-planar, high-temperature superconducting stellarator coils

“…Considerable efforts have been made to construct planar ReBCO coils for tokamak experiments [15][16][17], which are the most developed fusion concept. ReBCO is considered in the design of the central solenoid for the European DEMO reactor [18].…”

High-current, double-sided REBCO tapes by advanced MOCVD

“…Many designs of high-field magnets for particle accelerators and compact fusion reactors require bundled RE-Ba 2 Cu 3 O 7−δ (REBCO) tape strands [1][2][3][4][5][6]. For instance, over 200 tape strands are required for high current cables for compact fusion magnets to achieve high dipole fields [7]. Consequently, the cost of REBCO tapes dominates the cost of high-field magnets.…”