STRAND PRODUCTION AND BENCHMARK TESTING FOR THE ITER MODEL COILS

As part of the technology demonstration for the main features of the ITER Tokamak superconducting coils, two model roils, characteristic bore 2 divided by 3m, will be manufactured jointly by the four ITER partners (EC, JA, RF, US), The coils will require a total of 26 tonnes of Nb3Sn strand, supplied equally by each of the partners. The procurement of the strand is proceeding in stages, with performance and continuous quality demonstrated first on about It from each party underway since Sept, 93 and due for completion by Oct, 94. The strand uses both the bronze and internal tin routes, achieving jc(non copper) in the range 550-700 A/mm(2) 12T and 4.2K, with hysteresis losses from 200 to 600 mJ/cc(nonCu) for +/- 3T cycle. Unit lengths >1.5km are required with diameters about 0.8mm. The status and parameters achieved in the production is reported. One of the first steps in confirming the strand quality has been to establish consistent testing procedures through a benchmark activity using strand exchange between all parties. The first block of testing was completed in May 94 and a second round is now underway. The results of the two rounds and the steps taken to standardise the testing are described.