Abstract
Measurements and calculations are presented of the real ( χ′) and imaginary ( χ″) parts of the AC susceptibility of a monofilament silver-sheathed Bi-2223 tape as a function of temperature T=4–130 K, frequency ω/2 π=5 Hz–5 kHz and ac magnetic field amplitude μ 0 H m=0.02–7 mT. The susceptibilities consist of a hysteretic component due to induced currents in the superconductor core and an eddy current component due to induced eddy currents in the silver sheath. At high temperatures (>70 K) the low frequency limit is used to rigorously calculate the hysteretic and eddy current susceptibilities while at low temperatures the susceptibility is approximately described as being due to eddy currents flowing along the edges of the tape. The measured χ″ and hence AC loss at low frequencies (<50 Hz) and high temperatures is dominated by the hysteretic loss which varies with amplitude but is essentially independent of frequency. At higher frequencies and low temperatures, the eddy current loss of the silver sheath becomes dominant and increases with increasing frequency.
Published Version
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