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 coils, characteristic bore 2/spl divide/3 m, will be manufactured jointly by the four ITER partners. The coils will require a total of 26 tonnes of Nb/sub 3/Sn 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 1t 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(noncopper) in the range 550-700 A/mm/sup 2/ at 12 T and 4.2 K, with hysteresis losses from 200 to 600 mJ/cc(nonCu) for +/- 3 T cycle. Unit lengths >1.5 km are required with diameters about 0.8 mm. 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.<>