NbTivalues describe: Nb-47Ti
Big science (accelerators, light sources, public fusion)Quantum hardwareFusion, private
Why it wins
The ductile workhorse superconductor: magnet windings and the low-heat-leak wiring of dilution refrigerators.
Why not the alternative
Copper wiring is a heat pipe into the mixing chamber; Nb3Sn wire carries more field but is brittle and reaction-heat-treated.
Watch out
Needs 4 K class operation; field limit near 10 T.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated.
Provisional provenance: CERN Accelerator School, vacuum and materials proceedings.
Wet cleaning
| Recipe | as delivered; the insulation and the matrix govern |
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| Forbidden | solvents that attack the wire insulation |
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| Limit | insulation compatibility, not vacuum |
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Vacuum and outgassing
| Outgassing, unbaked (10 h) | 2e-9 mbar·L/s/cm² |
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| Outgassing, baked | 1e-11 mbar·L/s/cm² |
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| Vapour pressure | negligible |
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Temperature
| Bake, assembled | 200 °C |
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| Metallurgical limit | Tc 9.5 K; the Cu matrix anneals from 200 °C |
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Thermal
| CTE | ~8 ppm/K |
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| Thermal conductivity | 0.1 at 4 K W/m·K |
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Mechanical
| Strength | 700–1000 ys MPa |
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| Young's modulus | 80 GPa |
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| Density | 6 g/cm3 |
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Electrical and magnetic
| Relative permeability | type II, Bc2 ~11 T at 4.2 K |
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| Resistivity | zero below Tc |
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Engineering
| Joining | soldered joints and splices |
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| Process notes | lives in insulation vacuum, not process vacuum |
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| Availability and cost | commodity magnet wire |
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Grades
| Nb-47Ti multifilament in Cu matrix | magnets and current leads |
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| Nb-47Ti in CuNi matrix | cryostat wiring: low thermal conductance |
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Sources · 1
- CERN Accelerator School, superconductivity
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