REBCO Coated Conductor Development for Mass Productive Process Using IBAD and Hot-wall PLD

Nov. 29 16:40-17:05

*Yasuhiro Iijima1, M. Ohsugi1, K. Kakimoto1, S. Muto1, W. Hirata1, S. Fujita1, N. Nakamura1, S. Hanyu1, M. Daibo1
Fujikura Ltd.1

REBCO coated conductors by IBAD/PLD process have excellent and uniform in-field Jc properties with robust mechanical strain strength. They are suitable to varied field magnets especially for high field applications and implemented in the practical inner magnet coils for high-end NMR systems, which strongly requires good transporting and dimensional uniformity in long piece length. Moreover, tremendous REBCO conductor demands emerged recently for “compact” nuclear fusion prototype research which requires quite high in-field Ic even at 20 K, 20 T, within affordable cost and Ic variations. This talk describes current status and perspectives of REBCO coated conductor by mass productive PLD process at Fujikura Ltd. Pulsed-laser-deposition (PLD) is a non-equilibrium vapor process characterized to have high growth rate with quite largely supersaturated conditions though it has also excellent controllability of varied deposition conditions for complexed multi-element oxide films as REBCO. It allows to control high density crystalline dislocations and small-size secondary phase particles to a certain extent, dispersed inside good textured REBCO films growing at very high rates. It is so suitable to obtain desired flux pinning centers and in-field transporting current without severe degradation of matrix superconductivity and processing throughput. These PLD advantages should be guaranteed if the most severe parameter of substrate temperature were enough controlled during long length contentious depositions. Fujikura group had designed and developed “Hot-Wall Type” reel-to-reel PLD apparatuses, which realized quite robust and reproducible temperature uniformity by furnace like heating system. We succeeded to commercialization of long length and uniform REBCO wires including BaHfO3 doped artificial pinning type lineups, preserving deposition conditions within narrower windows by Hot wall PLD. It was also important to choose RE elements of Gd, or Eu, that the crystalline growth stability was so excellent that good c-axis aligned high quality thick films were reproducibly obtained by hot-wall PLD. Recent results of high field transporting characteristics for production wires would be presented. There are also some controversy for neutron radiation damage come from very large cross section of low energy (~1 eV) thermal neutron capture of Gd or Eu. But recent simulations suggested it would be not so severe matter because main radiation damage at fusion magnets should come from high energy (> 0.1 MeV) neutron bombardment, though sufficient experimental confirmations are not completed yet [1]. We are currently continuing to develop productivity and quality control of those wires toward large capacity and long piece length industrialization. We also completed line up of tape-width from 2 to 12 mm with commercial level quality, replying to the demand of narrow wide wires for loss reduction or field accuracy, etc. A part of this work is based on results obtained from a project subsidized by the New Energy and Industrial Technology Development Organization (NEDO). A part of this work was also performed at the High Field Laboratory for Superconducting Materials, IMR, Tohoku University.

References [1] W. Iliffe: “Radiation Damage of Superconducting Materials for Fusion Application,” Thesis for Ph. D., Univ. of Oxford, 2021

Keywords: BMO Doped REBCO, Coated Conductors, Hot-Wall PLD