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The tubular technique for economical production of Nb3Sn material with large numbers of subelements is being explored further by Supergenics I LLC and Hyper Tech Research Inc. The number of subelements has been raised to 271 (246 + 25) by increasing the size at which the restacking is carried out. The product exhibited no fabrication problems and was drawn down and tested at a wire diameter of 0.42 mm, where the subelements are 18 mum in diameter. Heat treatment of a 271 subelement restack has been varied and a pre heat treatment of 48 h at 575degC followed by long times at 635degC has been shown to be advantageous. Restacks with 217 subelements have been subjected to both compositional and heat treatment changes and the best results, closely approaching those found on PIT materials, have been found on samples given 500 h at 625degC.
Date of Publication: June 2009