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 niobium 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 Nb 3 Sn magnet conductors. Analyses of present materials show that P decreases systematically with billet mass. While production strands in 200–500 kg billets have costs times the cost of raw materials, the 20–50 kg billet size for internal-tin Nb 3 Sn 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, Nb 3 Sn 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 if a large-scale internal-tin or powder-in-tube Nb 3 Sn 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: Nb 3 Sn strands could reach $6 kA −1 m −1 at 12 T, 4.2 K, while Bi-2212 strands could fall below $10 m −1 . MgB 2 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 at 2 T, 4.2 K based on published data.