  This paper reports a newly developed high current transformer-rectifier
High-Tc Superconducting (HTS) flux pump switched by dynamic resistance. A
quasi-persistent current of over 1.1 kA has been achieved at 77 K using the
device, which is the highest reported operating current by any HTS flux pumps
to date. The size of the device is much smaller than traditional current leads
and power supplies at the same current level. Parallel YBCO coated conductors
are used in the transformer secondary winding as well as in the superconducting
load coil to achieve high current. The output current is limited by the
critical current of the load rather than the flux pump itself. Moreover, at
over 1 kA current level, the device can maintain high flux injection accuracy,
and the overall flux ripple is less than 0.2 mili-Weber. The work has shown the
potential of using the device to operate high field HTS magnets in ultra-high
quasi-persistent current mode, thus substantially reducing the inductance,
size, weight, and cost of high field magnets, making them more accessible. It
also indicates that the device is promising for powering HTS NMR/MRI magnets,
in which the requirement for magnetic field satiability is demanding.
