Progress on the conductor for the superconducting toroids of the ATLAS experiment

The production of the conductor for the superconducting toroids of the Atla s experiment at LHC (CERN) is under way, The conductor is obtained by coext ruding a big Rutherford cable with very pure aluminum, All toroids, one Bar rel Toroid (BT) and two End Cap Toroids (ECT), require a conductor with a c ritical current of about 60 kA at 5 T, 4.2 K and a RRR in-excess of 800 (at zero field), together with a very good bonding between cable and aluminum: 20 MPa for the BT and 15 MPa for the ECT, So far four long lengths, approx imately 7 km out of the 90 km of the total need, have been successfully pro duced, thus demonstrating the feasibility of the process. The paper describ es the results of the R&D phases and the results obtained in this first pro duction. The critical current degradation due to cabling and coextrusion wa s found quite moderate (7-8 % in total), despite the low copper content of the strands (Cu:NbTi = 1.09-1.18). The bonding was also very good with valu es well in excess of the specification. A special control system based on c ontinuous ultrasonic inspection was used in the coextrusion line to monitor the bonding quality in real time during production.