Abstract
Superconducting magnets are an invaluable tool for scientific discovery, energy research, and medical diagnosis. To date, virtually all superconducting magnets have been made from two Nb-based low-temperature superconductors (Nb-Ti with a superconducting transition temperature Tc of 9.2 K and Nb3Sn with a Tc of 18.3 K). The 8.33 T Nb-Ti accelerator dipole magnets of the large hadron collider (LHC) at CERN enabled the discovery of the Higgs Boson and the ongoing search for physics beyond the standard model of high energy physics. The 12 T class Nb3Sn magnets are key to the International Thermonuclear Experimental Reactor (ITER) Tokamak and to the high-luminosity upgrade of the LHC that aims to increase the luminosity by a factor of 5–10. In this paper, we discuss opportunities with a high-temperature superconducting material Bi-2212 with a Tc of 80–92 K for building more powerful magnets for high energy circular colliders. The development of a superconducting accelerator magnet could not succeed without a parallel development of a high performance conductor. We will review triumphs of developing Bi-2212 round wires into a magnet grade conductor and technologies that enable them. Then, we will discuss the challenges associated with constructing a high-field accelerator magnet using Bi-2212 wires, especially those dipoles of 15–20 T class with a significant value for future physics colliders, potential technology paths forward, and progress made so far with subscale magnet development based on racetrack coils and a canted-cosine-theta magnet design that uniquely addresses the mechanical weaknesses of Bi-2212 cables. Additionally, a roadmap being implemented by the US Magnet Development Program for demonstrating high-field Bi-2212 accelerator dipole technologies is presented.
Highlights
High-field superconducting magnets are a key component in many scientific and medical instruments, including particle accelerators [1], fusion energy reactors [2], magnetic resonance imaging (MRI) scanners, ion beam cancer therapy devices [3], as well as thousands of nuclear magnetic resonance (NMR) spectrometers
We will discuss the challenges associated with constructing a high-field accelerator magnet using Bi-2212 wires, especially those dipoles of 15–20 T class with a significant value for future physics colliders, potential technology paths forward, and progress made so far with subscale magnet development based on racetrack coils and a canted-cosine-theta magnet design that uniquely addresses the mechanical weaknesses of Bi-2212 cables
The present paper focuses on Bi-2212, which, similar to Nb-Ti and Nb3 Sn, is produced in an isotropic, round, multifilamentary form [17] that can be wound or cabled into arbitrary geometries including Rutherford cables, a flat rectangular cable simple and cheap to produce and composed of wires twisted and transposed for stability and high-field quality
Summary
High-field superconducting magnets are a key component in many scientific and medical instruments, including particle accelerators [1], fusion energy reactors [2], magnetic resonance imaging (MRI) scanners, ion beam cancer therapy devices [3], as well as thousands of nuclear magnetic resonance (NMR) spectrometers. After three decades of arduous conductor development, three high-temperature superconducting (HTS) cuprates (REBa2 Cu3 Ox (REBCO) (RE = rare earth), (Bi, Pb) Sr2 Ca2 Cu3 Ox (Bi-2223), and Bi2 Sr2 CaCu2 Ox (Bi-2212)) have been commercially made into practical forms of metal/superconductor composite conductors in lengths suitable for making magnets. They have been demonstrated to have a high current-carrying capability with the whole wire current density JE exceeding 100 A/mm at 4.2 or 1.8 K above 23 T, where the Jc of Nb3 Sn wires ceases to be useful. The paper will conclude with a technical roadmap being implemented at the US Magnet Development Program (MDP) [20], and synergetic developments
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