OPERATION LIMITS OF THE EURATOM LCT COIL AT HE-II TEMPERATURE

Within the framework of the IEA 'Large Coil Task' (LCT), on behalf of the European Union the Forschungszentrum Karlsruhe (FZK) constructed a D-shaped toroidal field coil using a forced flow cooled NbTi conducto r. The excellent performance and additional mechanical support structu re promised to achieve the outermost boundary operation limit for a la rge forced flow cooled magnet (20 kA at about 11 T). The TOSKA facilit y was modified for operation of forced flow He II. After a cool down t ime of about 290 h, the coil was operated at 3.6 K first to compare th e results with those obtained in ISMTF at ORNL. The coil showed a spon taneous quench of the high field pancake at 16.4 kA in full agreement with the critical current data measured at short sample strands. After cooldown to 1.8 K, the coil was ramped up with its current sharing re gion clearly visible on the resistive voltage. The quench started in t he high field pancake as expected, the inlet temperature was 1.89 K, t he current 19.45 kA, corresponding to a maximum magnetic field of 10.7 7 T. Comparison with single strand data extrapolated from 4.2 K measur ements showed no degradation. (C) 1998 Elsevier Science Ltd. All right s reserved.