Behavior of a high-temperature superconducting conductor on a round core cable at current ramp rates as high as 67.8 kAs(-1) in background fields of up to 19T

摘要

High temperature superconducting (HTS) conductor-on-round-core (CORC (R)) cables have been developed for use in power transmission systems and large high-field magnets. The use of high-current conductors for large-scale magnets reduces system inductance and limits the peak voltage needed for ramped field operation. A CORC (R) cable contains a large number of RE-Ba2Cu3O7-delta (RE - rare earth) (REBCO) coated conductors, helically wound in multiple layers on a thin, round former. Large-scale applications, such as fusion and accelerator magnets, require current ramp rates of several kilo-Amperes per second during pulsed operation. This paper presents results that demonstrate the electromagnetic stability of a CORC (R) cable during transient conditions. Measurements were performed at 4.2 K using a 1.55 m long CORC (R) cable in background fields of up to 19 T. Repeated current pulses in a background field of 19 T at current ramp rates of up to 67.8 kA s(-1) to approximately 90% of the cable's quench current at that field, did not show any sign of degradation in cable performance due to excessive ac loss or electromagnetic instability. The very high current ramp rates applied during these tests were used to compensate, to the extent possible, the limited cable length accommodated by the test facility, assuming that the measured results could be extrapolated to longer length cables operated at proportionally lower current ramp rates. No shift of the superconducting transition to lower current was measured when the current ramp rate was increased from 25 A s(-1) to 67.8 kA s(-1). These results demonstrate the viability of CORC (R) cables for use in low-inductance magnets that operate at moderate to high current ramp rates.