Technical Specification of Nb-Ti Strand and Rutherford Cable for MCBXF Corrector Magnets
The technical specs of the Nb-Ti strand and Rutherford cable for MCBXF corrector magnets are discussed, including details on strand characteristics, critical current, n-value, RRR, coating requirements, and more.
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Discussion about the technical specification of the Nb-Ti strand and Rutherford cable for the MCBXF corrector magnets
Suggested strand specs are based and those of LHC strand 5 in the Tech Spec EDMS No. 102992. C. Scheuerlein, WP 3 meeting, 22.4.2015
Cross section of LHC Nb-Ti strand 5 Nominal strand diameter is 0.48 mm. Nominal filament diameter is 6 m. Nominal copper to superconductor volume ratio is 1.75. Metallographic cross section of 05E00020A09SA C. Scheuerlein, WP 3 meeting, 22.4.2015
Main characteristics of LHC strand 5 (from EDMS No. 102992) C. Scheuerlein, WP 3 meeting, 22.4.2015
Critical current and n-value EDMS No. 102992: The minimum specified critical current as measured by CERN for Strand 5 is 189 A at 1.900 K and 8 T and 194 A at 5 T and 4.222 K . Is 194 A at 4.222 K and 5 T good enough? The variation in critical current of Strand 5 between 5 T, 4.222 K and 8 T, 1.900 K depends on the strand manufacturing process. Therefore the minimum critical current value of 194 A at 4.222 K and 5 T for Strand 5 may have to be increased in order to get the required minimum critical current value of 189A at 1.900 K and 8 T. Since the manufacturer is expected to perform critical current measurements only at 4.222 K, the minimum critical current at 4.222 K and 5 T for Strand 5 will be reviewed and fixed for the Contractor after the manufacturing of strands from the first five billets. CERN has a high interest to increase the critical current of Strand 5. The tenderer will therefore be invited to make an additional quote for a higher critical current. The "n" value must be determined in the range from 10 V/m to 100 V/m at each applied field and must be greater than 40 at 5 T . C. Scheuerlein, WP 3 meeting, 22.4.2015
Residual Resistivity Ratio (RRR) of the Cu stabiliser EDMS No. 102992: must be larger than 150 for annealed strands . Do we need RRR>150 after strand annealing (before cabling)? Will there be a second annealing after cabling? IEEE Xplore Full-Text PDF: - Internet Explorer From Z. Charifoulline IEEE Trans. Appl. Supercond. 16(2), (2006)
Is a strand coating needed for the MCBXF cables? EDMS No. 102992: The individual strands shall be coated with SnAg (5wt % Ag) alloy having a maximum thickness of 1 m and a minimum thickness of 0.1 mm . to obtain an interstrand cross-contact resistance of 40 . Is this tight control of the interstrand resistance needed for the MCBXF cables? Very roughly it is estimated that the cost of the coating is between 10-20% of the strand cost without coating. Higher quality double run coating for 150 km strand is about 60 000 CHF more expensive than single run coating . A cable air HT is needed in order to transform the coating into an oxidised Cu3Sn intermetallic layer that provides the desired electrical resistance and stability. C. Scheuerlein, WP 3 meeting, 22.4.2015
Cable characteristics What are the cable dimension tolerances? Anything else to specify?
Quantities and schedule June 2015: January 2016: 5 UL 400 m (about 2 km cable; about 40 km strand) Today we have about 240 km strand diameter 0.48 mm on stock (Info A. Bonasia) 3 UL 420 m, 3 UL 560 m (about 3 km cable; about 60 km strand) January 2017: 12 UL 700 m, 12 UL 920 m (about 20 km cable; about 400 km strand) October 2017: 70 UL 400 m, 24 UL 560 m (about 29 km cable; about 580 km strand) January 2018: 24 UL 420 m, 24 UL 560 m (about 24 km cable; about 480 km strand) Total: 153 UL with a total length of about 75 km cable Roughly 1500 km strand need to be purchased C. Scheuerlein, WP 3 meeting, 22.4.2015
