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APPLIED SUPERCONDUCTIVITY 2009Critical current measurements on Bi-2212High critical temperature superconductors (HTS) open extremelyinteresting perspectives for high magnetic field applicationssuch as high field magnets for NMR or SMES,nuclear fusion, or future colliders. The demand is high for25−50 T magnets which is beyond the possibilities offeredby low critical temperature superconductors, i.e. Nb 3 Sn.The possibility of precisely measuring the rather elevatedcritical currents of superconductors in a high magnetic fieldenvironment is crucial for the development of HTS magnets.(length 30 mm) can be seen in figure 1. The results havebeen checked by performing cross characterizations at theSACM, CEA Saclay.Complete characterization of Bi-2212 and YBaCuO wiresand tapes at high magnetic fields and low temperatures(from 4.2 to 80 K) can be performed using this new VTI,which will be a very useful tool for the studies of HTS inthe frame of the SUPER-SMES project.Interest for Bi-2212 round wire for high magnetic field applicationsincreased recently due to the wires outstandingperformance concerning their intrinsic transport properties.The critical current density is higher than 1000 MA/m 2at 4.2 K and 45 T. Equally the second generation (2G)of YBaCuO coated HTS conductors, show very promisingperformances in terms of critical currents under very highmagnetic fields. In addition, their mechanical properties areexcellent for the ion beam assisted deposition (IBAD) route.The mechanical performances are of great importance forvery high field magnets. Significant progress has also beenachieved in terms of lengths, to the point where it it is nowpossible fabricate HTS magnets. The possibility to operateat higher temperatures than 4.2 K improves considerablythe stability of the magnet due to the rapid increase of thespecific heat at higher temperatures. The stability is one ofthe limitations of LTS magnets in term stored magnetic energyper unit mass. On the other hand the protection of themagnet is much more difficult since the propagation velocitiesare low, leading to a difficult detection of any quench.HTS magnet protection has been identified as an issue fortheir development.The HTS wires (BiSrCaCuO PIT or YBaCuO coated conductor)are produced by Nexans or other providers (suchas OST). The typical cross section of the tapes is 4 ×0.1/0.2 mm 2 and a diameter of 1 mm for the round wires.The critical current is of the order of ∼ 500 A in theself-field at 4.2 K. In the frame of the ANR “SUPERSMES” contract, a new Variable Temperature Insert hasbeen built in collaboration between LNCMI and the NéelInstitute. The available space has been optimized to maximizethe sample length: a 34 mm long sample can betested in the 39 mm diameter field bore. An investigationof the sample anisotropy is possible, since the sample canbe rotated through 90 ◦ . Critical currents are measured atthe LNCMI under fields up to 20 T. The sample holderhas been designed to enable measurements on a VAMASlikecoil sample. Preliminary measurements performed onBi-2212 VAMAS sample (length 1 m) and short samplesFigure 150: (a) Transport I c versus magnetic field at differenttemperatures in parallel orientation for a VAMAS Bi-2212 tape.(b) Transport I c versus magnetic field at different temperatures inparallel orientation for a short Bi-2212 sample.E. Mossang, F. Debray, J.P. Domps, S. DufresnesP. Brosse-Maron, O. Exshaw, P. Gandit, L. Porcar, P. Tixador (Institut Néel, CNRS, Grenoble, France), J.M. Rey(DSM-DAPNIA-SACM, CEA Saclay, France)104