Development of a novel joint-less double aperture REBCO magnet with an innovative excitation circuit for stable magnetic field generation

Abstract

Second-generation high-temperature superconducting (2G-HTS) magnets operating in persistent current mode (PCM) effectively address the challenge of magnetic field stability. This paper introduces a novel joint-less double aperture (JDA) REBa₂Cu₃O_7−δ (REBCO, RE: rare earth) magnet, designed to overcome the limitations posed by joint resistance in traditional 2G-HTS magnets. A single slit REBCO tape is innovatively wound into double-pancake (DP) coils on both sides and placed in spaced apertures within the magnet. This closed-loop design generates two stable magnetic fields while effectively preventing tape twisting between the DP coils. Furthermore, a new portable excitation circuit is proposed for the JDA REBCO magnet, utilizing pulsed magnetic fields generated by the copper coil, which eliminates the need for current leads, electrodes, and persistent current switches (PCSs), significantly reducing system complexity. Initially, a traditional PCS was used to charge the JDA REBCO magnet to 40 A at 77 K, generating a magnetic field of 60.6 mT at the center of one of the DP coil apertures. The magnet was then successfully excited using a pulse circuit after about 200 cycles. A comparative analysis with the PCS results showed that the current induced by the pulse circuit was approximately 40 A. The stability of the magnetic field within one DP coil of the JDA REBCO magnet was monitored for 107 h, with a magnetic field drift rate of approximately 0.86 ppm/h. The closed-loop advantage of the JDA REBCO magnet, combined with the portable pulsed excitation circuit, demonstrates the promising potential for applications in double aperture magnetic resonance imaging (MRI) equipment, particle accelerators, and other advanced technologies.