An initial magnet experiment using high-temperature superconducting STAR® wires

Abstract

A dipole magnet generating 20 T and beyond will require high-temperature superconductors such as Bi2Sr2CaCu2O8-x and REBa2Cu3O7-x (RE = rare earth, REBCO). Symmetric tape round (STAR®) wires based on REBCO tapes are emerging as a potential conductor for such a magnet, demonstrating a whole-conductor current density of 580 A mm-2 at 20 T, 4.2 K, and at a bend radius of 15 mm. There are, however, few magnet developments using STAR® wires. Here we report a subscale canted cosθ dipole magnet as an initial experiment for two purposes: to evaluate the conductor performance in a magnet configuration and to start developing the magnet technology, leveraging the small bend radius afforded by STAR® wires. The magnet was wound with two STAR® wires, electrically in parallel and without transposition. We tested the magnet at 77 and 4.2 K. The magnet reached a peak current of 8.9 kA, 78% of the short-sample prediction at 4.2 K, and a whole-conductor current density of 1500 A mm-2. The experiment demonstrated a minimum viable concept for dipole magnet applications using STAR® wires. The results also allowed us to identify further development needs for STAR® conductors and associated magnet technology to enable high-field REBCO magnets.

A 6-around-1 cable using high-temperature superconducting STAR ® wires for magnet applications

“…Therefore, we explore concepts for a high-current and flexible cable using multiple star ® wires. One example is a ribbon cable using two wires [17]. The wires, however, are not transposed in a ribbon cable.…”

High critical current STAR® wires with REBCO tapes by advanced MOCVD

“…The magnet used two STAR ® wires, electrically in parallel in each layer, and the minimum bending radius was 15 mm at the pole region of the magnet. The magnet showed reproducible current-voltage transitions with a maximum transport current of 8500 A at 4.2 K, with no obvious wire degradation after winding, even at the 15 mm bend radius [8].…”

“…Recently, LBNL demonstrated a two-layer subscale CCT dipole magnet with three wire turns in each layer [8]. The magnet used two STAR ® wires, electrically in parallel in each layer, and the minimum bending radius was 15 mm at the pole region of the magnet.…”

An Initial Look at the Magnetic Design of a 150 mm Aperture High-Temperature Superconducting Magnet With a Dipole Field of 8 to 10 T

“…When the groove contains a single stack of wires, if Wire 1 at the bottom of the groove follows (2) with r 1 and θ 1 , then we have tan θ n / tan θ 1 = r n /r 1 for Wire n [29], [55].…”

“…The U.S. Magnet Development Program, in collaboration with conductor vendors, is working to generate a dipole field of 5 T [25]- [29].…”