  MgB2 is a promising superconductor for important large-scale applications for
both high field magnets and cryocooler-cooled magnet operated at temperatures
around 20 K. In this work, by utilizing C60 as a viable alternative dopant, we
demonstrate a simple and industrially scaleable rout that yields a 10-15-fold
improvement in the in-high-field current densities of MgB2 tape conductors. For
example, a Jc value higher than 4x10^4 A/cm^2 (4.2 K, 10 T), which exceeds that
for NbTi superconductor, can be realized on the C60 doped MgB2 tapes. It is
worth noting that this value is even higher than that fabricated using strict
high energy ball milling technique under Ar atmosphere. At 20 K, Hirr was about
10 T for C60 doped MgB2 tapes. A large amount of nanometer-sized precipitates
and grain boundaries were found in MgB2 matrix. The special physical and
chemical characteristic of C60, in addition to its C containing intrinsic
essence, is a key point in enhancing the superconducting performance of MgB2
tapes.
