Costs of high-field superconducting strands for particle accelerator magnets

• Published in: Superconductor science & technology 2005-04, Vol.18 (4), p.R51-R65
• Main Authors: Cooley, L D, Ghosh, A K, Scanlan, R M
• Format: Article
• Language: English
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/18/4/R01

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 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 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 Jc 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 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 at 2 T, 4.2 K based on published data.