Is hybrid design really a better solution for a 12.5 T magnet?
Mixing two technologies may create complications. Also a larger required volume of NbTi conductor makes the support structure and magnet bigger.
Jc of Nb3Sn at 8 T (field in outer coil) is over 4 times that of NbTi.
Compare the cost of the same size (0.8 mm) wire per meter (remember much more NbTi is needed)
- NbTi: ~$0.65/m
- Nb3Sn: ~$3.50-$4.00/m (DOE Goal ~$1/m)
- Copper, by weight, is about an order of magnitude cheaper. The effective cost of Nb3Sn can be significantly reduced by mixing it.