  The in-field critical current of commercial YBa2Cu3O7 coated conductors can
be substantially enhanced by post-fabrication irradiation with 4 MeV protons.
Irradiation to a fluence of 8x10^16 p/cm^2 induces a near doubling of the
critical current in fields of 6 T || c at a temperature of 27 K, a field and
temperature range of interest for applications such as rotating machinery. A
mixed pinning landscape of preexisting precipitates and twin boundaries and
small, finely dispersed irradiation induced defects may account for the
improved vortex pinning in high magnetic fields. Our data indicate that there
is significant head-room for further enhancements.
