ac losses of superconducting solenoidal coils

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Abstract
Ac losses of superconducting solenoidal coils were investigated with a calorimetric method while applying a current or uniform magnetic field of 50 Hz with a sinusoidal wave form. The peak value of the ac current was varied from 0 to 15 rms A and that of the ac magnetic field from 0 to 0.02 T. These experimental conditions are for a practical regime where loss theories are difficult to apply and empirical data of the type generated are directly useful. Nine coil samples of various sizes were constructed with different fine multifilamentary superconducting wires. The ac losses observed are proportional to the square of the amplitude of an applied ac magnetic field or an applied ac current and appear to be mainly eddy current losses. The ac losses of coils of the same size caused by an applied ac current were the same regardless of the kind of wire used. All losses in the superconducting coils appeared to be equivalent to those expected from eddy currents in solid copper wires 0.72 times the diameter of the wires used, independent of the wire size and internal configuration.