Calculations of AC magnetic losses from the experimental field profiles in various types of coated conductors under applied fields

다국어 초록 (Multilingual Abstract)

<P>We measured the field profiles, <I>H</I>(<I>x,H</I><SUB>a</SUB>) s, near the surface of coated conductors (CCs) by using the scanning Hall probe method. The samples were SmBCO-CC tape fabricated by co-evaporation method and YBCO-CC tape fabricated by PLD method. The applied fields, <I>H</I><SUB>a</SUB>s, were decreased from <I>H</I><SUB>peak</SUB>to -<I>H</I><SUB>peak</SUB> stepwise. From the values of <I>H</I>(<I>x,H</I><SUB>a</SUB>), we calculated the current profiles, <I>J</I>(<I>x,H</I><SUB>a</SUB>) s, by the inversion method. From the values of <I>J</I>(<I>x,H</I><SUB>a</SUB>) and the corresponding flux densities, we calculated the hysteretic energy losses per cycle, <I>Q</I><SUB>M</SUB>s, for various <I>H</I><SUB>peak</SUB>s. From the values of <I>Q</I><SUB>M</SUB>, we calculated the characteristic functions, <I>g</I>s, by using the relation, <I>g</I>= π<I>Q</I><SUB>M</SUB>/μ<SUB>0</SUB><I>I</I><SUP>2</SUP><SUB>c</SUB>. Here, <I>I</I><SUB>c</SUB> is the critical current. For the range of <I>H</I><SUB>peak</SUB>/<I>H</I><SUB>c</SUB>≤ 3, the <I>g</I>-values of SmBCO CC tape were larger than those of YBCO CC tape. However, for the range of <I>H</I><SUB>peak</SUB>/<I>H</I><SUB>c</SUB> ≥ 3, the <I>g</I>-values of SmBCO CC tape were smaller than those of YBCO CC tape. When <I>H</I><SUB>peak</SUB>/<I>H</I><SUB>c</SUB> = 3, both sample show almost same value of <I>g.</I>However we found qualitatively different <I>J–B</I> hysteretic curves for both samples. We also compared our <I>g</I>-values with other <I>g</I>-values, which were directly measured by energy loss experiments. Our <I>g</I>-values of YBCO CC tapes were basically similar to the Brandt's theoretical values of <I>g</I> in the most range of <I>I</I><SUB>peak</SUB> in our measurements.</P>