Critical Current Density and Current Transfer Length of Multifilamentary $\hbox{MgB}_{2}$ Strands of Various Design

Abstract

In this paper, a series of high-performing powder-in-tube MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> strands have been prepared. Transport voltage-current measurements were performed to determine the effects of C doping and strand geometry such as filament numbers. The best <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> for our samples was 1.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K, 7 T, for a strand using B powder with 3% C addition. The current transfer length was also measured for MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> short wires with Nb chemical barrier and Monel outer sheath. The current transfer length ranged from 2 to 12 mm, and had a correlation with the filament numbers.