Conceptual Design of a HTS Dipole Insert Based on Bi2212 Rutherford Cable

Abstract

The U.S. Magnet Development Program (US-MDP) is aimed at developing high-field accelerator magnets with magnetic fields beyond the limits of Nb3Sn technology. Recent progress with composite wires and Rutherford cables based on the first generation high-temperature superconductor Bi2Sr2CaCu2O8−x (Bi2212) allows considering them for this purpose. However, Bi2212 wires and cables are sensitive to transverse stresses and strains, which are large in high-field accelerator magnets. This requires magnet designs with stress management concepts to control azimuthal and radial strains in the coil windings and prevent the degradation of the current carrying capability of Bi2212 conductor or even its permanent damage. This paper describes a novel stress management approach, which was developed at Fermilab for high-field large-aperture Nb3Sn accelerator magnets, and is now being applied to high-field dipole inserts based on Bi2212 Rutherford cables. The insert conceptual design and main parameters, including the superconducting wire and cable, as well as the coil stress management structure, key technological steps and approaches, test configurations and their target parameters, are presented and discussed.

Quench Detection and Protection for High-Temperature Superconductor Accelerator Magnets

“…Once a resistive zone appears, the current flow redistributes outwards from this zone, becoming asymmetric with respect to the conductor central axis. If the HTS conductor is a multi-strand cable (of Rutherford [14,32], Roebel [33,34], CORC ® [35,36], twisted stack [37] or other type), then the redistribution is generally also a function of inter-strand resistance, and a complex current flow pattern may form as a result. It should be noted that in the case of good current sharing (i.e., very low inter-strand resistance), current inhomogeneity is expected to be most apparent at a As magnet inductance L scales with the magnet size, τ e can be reduced either by increasing R mag (t) by some active means, such as the use of protection heaters [30] or induced coupling losses [31], or by increasing R dump .…”

“…Since their initial discovery in 1986, high-temperature superconductors [1] have made a long way toward practical use in applications, such as record-field solenoids [2][3][4], energy storage [5], fault current limiters [6][7][8] and transmission lines [9,10]. More demanding applications, such as high-field magnets for particle accelerators, are presently on the horizon [11][12][13][14][15], where HTS conductors will operate close to their stress limits, and will have to satisfy necessary mechanical, electromagnetic and thermal stability criteria. One key aspect of a safe and reliable operation of any accelerator magnet is the ability to sustain and mitigate spontaneous quenching-a phenomenon where one or several superconducting strands suddenly transition into a normal state.…”

Development of a 120-mm Aperture Nb3Sn Dipole Coil With Stress Management

“…The SMCT coil is a new concept which was proposed at Fermilab for high-field and/or large-aperture accelerator magnets based on low-temperature and high-temperature superconductors [10], [11]. The SM structure is used to reduce large coil deformations under the Lorentz forces and, thus, the excessively high stresses in the coil and a separation of pole turns at high fields.…”

Using additive manufacturing technologies in high-field accelerator magnet coils

“…The SMCT coil winding will start shortly after parts post-processing. Parts for the Bi2212 insert coil [12] to be produced using AM technology are now being designed and optimized using practice plastic parts.…”