Ac losses in multifilamentary high-TC tapes due to a perpendicular ac magnetic field

Ac losses in mono and multifilamentary high-TC tapes exposed to a harmonic magnetic field perpendicular to he tape surface are considered. By writing the ac dissipation in terms of the ac magnetic susceptibility, we have two parameters: the imaginary part of the internal ac susceptibility χ'' and the external susceptibility in the Meissner state χ0, related to the demagnetization. These two terms of the ac loss formula are analysed in detail through both theoretical and experimental approaches. We have used finite-element codes to determine χ0 for the three tapes under study, and then we have compared the predictions and the experimental results. Existing theories have been used to calculate χ'' as a function of the amplitude of the ac magnetic field and have been verified through measurements. (author)