Costs of high-field superconducting strands for particle accelerator magnets

The costs of superconducting magnet strands are compared by calculating a 'production scaling factor' P that relates purchase data to the cost of raw materials. Using a consistent method, we normalize for different conductor geometries and strand diameters to arrive at cost indices in $ kg(-1), $ m(-1), and $ kA(-1) m(-1). Analyses of Nb47Ti conductors taken from the past 25 years of high-field magnet projects reveal that the price of raw materials and, to a lesser extent, finished strands, have tracked the price of niobiurn pentoxide. Performance gains during the 1980s produced $ kA(-1) m(-1) indices that fell with time ahead of strand cost in $ m(-1), a situation that may reflect the present status of Nb3Sn magnet conductors. Analyses of present materials show that P decreases systematically with billet mass. While production strands in 200-500 kg billets have costs similar to 3 times the cost of raw materials, the 20-50 kg billet size for internal-tin Nb3Sn composites drives P up to 8-10. Thus, in contrast to LHC-type Nb47Ti strands that cost $150 kg(-1), $0.60 m(-1), and $1.00 kA(-1) m(-1) at 5 T, 4.2 K, Nb3Sn strands required for the next generation of accelerator magnets are $1000 kg(-1), $4.00 m(-1), and > $5.75 kA(-1) m(-1) at 12 T, 4.2 K (where J(c) is comparable to that for Nb47Ti at 5 T, 4.2 K). This high cost might be reduced by a factor of similar to 3 if a large-scale internal-tin or powder-in-tube Nb3Sn process can be found. Replacing expensive components with functionally equivalent but cheaper materials can produce 20% changes in $ kg(-1) and $ m(-1), but this might come at a performance penalty and no net savings in $ kA(-1) m(-1). Removing stabilizer from the strand cross-section and replacing it elsewhere in the cable can reduce the cost for a given length of cable significantly, but only if the processing cost for the strand remains unchanged after reduction of the stabilizer area. Emerging powder-in-tube composites show promise: Nb3Sn strands could reach $6 kA(-1) m(-1) at 12 T, 4.2 K, while Bi-2212 strands could fall below $10 m(-1). MgB2 superconducting strands could have very low raw materials cost at $0.20 m(-1), which translates to $1.00 m(-1) for finished strands and similar to$1.00 kA(-1) m(-1) at 2 T9 4.2 K based on published data.