Superconductor Manufacturing
VERTICAL INTEGRATION
Highfield Magnetics does not buy superconductor tape from the supply chain. We manufacture our own wire. This vertical integration was not originally planned — it became necessary when commercial REBCO tape suppliers could not meet the critical current density, dimensional tolerance, and substrate specifications required for the Iron Horse and ISO-1 product lines. Rather than accept compromised magnets, Highfield built a tape factory.
The REBCO coated conductor tape is 12mm wide and 0.1mm thick. The superconducting layer — rare earth barium copper oxide — is approximately 1 micron thick, deposited by pulsed laser deposition onto a multilayer buffer stack that sits on the substrate. The substrate is everything: it determines whether the tape survives the mechanical loads of a 100T magnet winding, whether it maintains dimensional stability during thermal cycling, and whether the buffer layer lattice-matches closely enough to grow a high-quality REBCO film.
SUBSTRATE: MS-19 TUNGSTEN-RHENIUM ALLOY
Supplied by Metallic Sciences Levitation Foundry
Standard commercial REBCO tape uses Hastelloy or stainless steel substrates — adequate for low-stress applications, insufficient for extreme-field magnets. Highfield's tape uses Metallic Sciences MS-19 tungsten-rhenium alloy substrate: a proprietary W-26Re composition developed specifically for this application. MS-19 offers tensile strength exceeding 2,000 MPa at 20K, coefficient of thermal expansion matched to the REBCO buffer stack to within 0.3 ppm/K, and surface roughness below 2 nm Ra after electropolishing — necessary for defect-free buffer layer nucleation. The substrate tape is drawn and rolled at the Metallic Sciences Levitation Foundry, which is co-located with Highfield's REBCO deposition line for substrate supply without atmospheric exposure between processes.
CRITICAL CURRENT PERFORMANCE
500 A/cm-width at 77K Self-Field
The production specification is 500 amperes per centimeter of tape width at 77K in self-field. In applied field environments (inside the magnet bore), critical current degrades with field angle — the REBCO layer exhibits strong c-axis pinning (field perpendicular to tape face) and weaker ab-plane performance (field parallel to face). Highfield's vortex pinning engineering introduces columnar defects via heavy-ion irradiation at specific crystal orientations, creating anisotropic pinning landscapes that flatten the angular dependence. The result: usable critical current at high field angles improves by 40% compared to non-engineered baseline tape.
PRODUCTION SCALE
200 km of Tape Per Year — Scaling to 2,000 km
Current annual production is 200 kilometers of tape per year, sufficient to supply internal magnet production and limited external sales. The compact fusion industry requires 100x this throughput within five years. Highfield's scale-up program (outlined in Field Dispatch // 005) runs three parallel tracks: deposition rate increase from 10 to 40 m/hour via advanced process control, substrate width expansion from 12mm to 100mm enabling slit-and-ship production of eight standard tapes per deposition run, and real-time X-ray diffraction analysis stations that catch crystallographic defects before they propagate through a kilometer of tape. The wire factory co-location with Metallic Sciences' Levitation Foundry is a structural advantage: substrate arrives warm and clean, enters deposition within minutes, eliminating the surface contamination that plagues supply-chain tape production.