This Small Business Innovation Research (SBIR) Phase I project will develop prototype MgB2 wires for next generation cryogen-free 1.5 Tesla (T) and 3.0 T magnetic resonance imaging (MRI) systems, by adding both magnetic and nonmagnetic impurities. These impurities will amplify the vortex pinning due to magnetic impurities, while compensating the concomitant magnetic impurity-induced transition temperature reduction with nonmagnetic impurities. This new technique will lead to a significant enhancement of high field properties of type II superconductors (i.e. increased critical current densities and upper critical fields). This conversion of ordinary superconductors into magnetic superconductors will open a new frontier for superconducting magnet technology. This SBIR project employs optimization of a sintering and manufacturing process for prototype MgB2 wires to guarantee the homogeneous dispersion of impurities along the wire and to achieve the maximal critical current density in a cost efficient way. This project will determine the optimum sintering conditions (i.e., temperature, pressure, and time), utilizing liquid phase sintering of impurities, and will test both in-situ and ex-situ powder-in-tube (PIT) manufacturing processes for producing the highest critical current densities in MgB2 wires.
The broader impact/commercial potential of this project includes the possibility of fabricating next-generation cryogen-free 1.5T and 3.0T MRIs, using the resulting MgB2 wires. The low-cost next-generation MRIs will replace the current Nb-Ti-magnet based MRIs, enhancing the public health significantly, because these envisioned MRIs will operate at a higher temperature, 20 K, obviating the need for expensive liquid helium. The elimination of liquid helium cryogen will lead to simple and versatile designs and almost maintenance-free operation, reducing the MRI scan cost up to 40%. The resulting prototype MgB2 wires will be also crucial for next generation of cryogen-free magnets for nuclear magnetic resonance (NMR), particle accelerators, and fusion reactors. Additionally, it is straightforward to apply this technique to Nb-Ti and Nb3Sn magnet materials. Accordingly, this novel technique has the potential to revolutionize superconducting magnet technology and opens a new research field of converting ordinary superconductors into magnetic superconductors. MgB2 wires are a viable candidate for follow-on applications in electric power transmission, superconducting fault current limiters, generators, and motors, all of which could be enabled by this innovative technique.
Cutting Edge Superconductors (CES) has manufactured several 30ft-110ft long prototype MgB2 wires for next generation cryogen-free 1.5T and 3T MRI, in collaboration with LUVATA. Ni and Cu/Nb were used for the sheath materials, i.e., Ni/MgB2 and Cu/Nb/MgB2. Both magnetic and nonmagnetic impurities were added to MgB2 wires to enhance high magnetic field properties, according to the worldwide patent of CES. The ex-situ powder-in-tube (PIT) manufacturing process has been found to be the only viable option for homogeneous dispersion of impurities along the wire, required by this new technology. The optimum sintering condition is also determined, although the liquid phase sintering needs more detailed study. The feasibility and the scalability of this new technique have been successfully proved. Any portion of the 30ft–110ft long wires show the consistent property, i.e., the same transition temperature, confirmed by magnetization measurements and resistance measurements. For critical current, IC, measurements, the wires were pressed into tapes and tested at the Applied Superconductivity Center at FSU. At 4.2K, the best Ni/MgB2 monofilament tape shows higher critical currents, IC, for any magnetic fields and superb magnetic field dependence, when compared to the multifilament tapes of Columbus Superconductors, as shown in Fig. 1. Better quality control of the manufacturing process of MgB2 wires and tapes will easily increase Ic a few times, enabling Next Generation Cryogen-free 1.0T Open MRI and 1.5T Closed MRI immediately. Accordingly Cutting Edge Superconductors announces that the Next Generation cryogen-free 1.0T Open MRI and 1.5T Closed MRI will hit the market next year, 2015. Cu/Nb/MgB2 tapes have excellent mechanical properties, although they are more sensitive to tape manufacturing process and require more development. In conclusion, this Small Business Innovation Research (SBIR) Project has successfully demonstrated that this new technology will revolutionize superconducting magnet technology and related industries.
