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To explore the limits of layer wound (RE)Ba 2 Cu 3 O 7-x (REBCO, RE = Rare Earth) coils in a high magnetic field environment > 30 T, a series of small insert coils have been built and characterized in background fields. One of the coils repeatedly reached 35.4 T using a single ~100 m length of REBCO tape wet wound with epoxy and nested in a 31 T background magnet. The coil was quenched safely several times without degradation. Contributing to the success of this coil was the introduction of a thin polyester film that surrounded the conductor. This approach introduces a weak circumferential plane in the coil pack that prevents conductor delamination that has caused degradation of several epoxy impregnated coils previously made by this and other groups.The cuprate based high temperature superconductor (RE)Ba 2 Cu 3 O 7-x (REBCO, RE = Rare Earth), has the capability to substantially transform the technology of high field magnet systems. So far, the low temperature superconductors Nb-Ti and Nb 3 Sn have been used for virtually all superconducting high field magnets. Their maximum field, however, is limited by their upper critical fields (H c2 ) of about 15 T for Nb-Ti and 30 T for Nb 3 Sn, which limits their highest practical field to about 23.5 T 1 . This limit is imposed by the rapid decrease in critical current density J c as H c2 is approached. By contrast, REBCO has an H c2 that exceeds 100 T at 4.2 K, removing the H c2 and J c limit that restricts usage of Nb 3 Sn in highfield magnet systems. One of the goals at the NHMFL is to develop the necessary technology for the next generation of high-field magnets including Nuclear Magnetic Resonance (NMR) quality magnets. To reduce the number of resistive joints and achieve the required field homogeneity for NMR, layer-winding

We present very high field angle dependent critical current density (J c ) data for three recently obtained YBa 2 Cu 3 O 7−x (YBCO) coated conductors used in the construction of high field solenoids. We find that strongly correlated pins, such as BaZrO 3 (BZO) nanorods, while yielding strong c-axis peaks at 77 K, produce almost no measurable contribution at 4 K. Raising the field from <5 to 30 T at 4 K causes a marked transition from a Ginzburg-Landau-like J c (θ ) at low fields to a marked cusp-like behavior at high fields. Transmission electron micrographs show that all samples contain a high density of stacking faults which strengthen the plane correlated pinning parallel to the ab planes produced by the intrinsic ab-plane pinning of the Cu-O charge reservoir layers.