Presentation Information
[WB7-03]Observation of delamination in the REBCO tapes used in the Resistive-Insulated-Nested-Coils (RINC)
*JUN LU1, Iain R Dixon1, Kwangmin Kim1, Yan Xin1, Hongyu Bai1 (1. National High Magnetic Field Laboratory (United States of America))
Keywords:
REBCO,Delamination,Magnetization,SEM,TEM
REBCO coated conductors have the potential to be widely used in ultrahigh field magnets for nuclear fusion, particle accelerators, NMR and MRI applications. It is well known, however, that they are not mechanically strong against delamination in the direction normal to its surface due to their intrinsic layered structures. For instance, severe degradation due to delamination was reported in epoxy impregnated coils in 2010. Since then, delamination has become one of the major design challenges of REBCO magnet coils.
As a part of the development of the 40 T all-superconducting magnet at the National High Magnetic Field Laboratory, USA , a dry-wound resistive-insulated-nested-coils was designed to reach 26 T using surface-treated stainless-steel tape as co-wind to control the turn-to-turn contact resistance. It was fabricated and tested in liquid helium bath. Two of the double pancake modules exhibited resistive transitions at a current significantly lower than the designed value. The postmortem inspection of the REBCO tapes by reel-to-reel magnetization tests at 77 K found sections of the conductor that have much lower critical current than the as-received values. Further investigations revealed that conductor delamination was the cause of the critical current degradation. In this presentation, the results of reel-to-reel magnetization, transport critical current test, and microanalysis of the delaminated REBCO tape will be shown. The implication of the delamination issue for future magnet designs will be discussed.
As a part of the development of the 40 T all-superconducting magnet at the National High Magnetic Field Laboratory, USA , a dry-wound resistive-insulated-nested-coils was designed to reach 26 T using surface-treated stainless-steel tape as co-wind to control the turn-to-turn contact resistance. It was fabricated and tested in liquid helium bath. Two of the double pancake modules exhibited resistive transitions at a current significantly lower than the designed value. The postmortem inspection of the REBCO tapes by reel-to-reel magnetization tests at 77 K found sections of the conductor that have much lower critical current than the as-received values. Further investigations revealed that conductor delamination was the cause of the critical current degradation. In this presentation, the results of reel-to-reel magnetization, transport critical current test, and microanalysis of the delaminated REBCO tape will be shown. The implication of the delamination issue for future magnet designs will be discussed.