Development of High Superconductor Fraction ${\hbox{Bi}}_{2}{\hbox{ Sr}}_{2}{\hbox{CaCu}}_{2}{\hbox{O}}_{\rm x}/{\hbox{Ag}}$ Wire for MRI

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Bi2212 round multifilament wire has good potential for MRI systems designed to operate at 20 K and produce fields greater than 1.5 T. However, Bi2212 conductor is expensive largely due to the costs associated with materials and fabrication. To reduce the cost, we are investigating single restack designs. This approach reduces the silver fraction. It also reduces the amount of processing needed to make the conductor. However, a single restack limits the minimum filament diameter that can be achieved since the strain space is more limited. In this work we evaluated 4 conductor configurations to determine the effects of fill-factor, filament diameter, and s/d on <formula formulatype="inline"> <tex>${\rm J}_{\rm e}$</tex></formula> and n value. It was found that a reduction in filament size has a greater effect on <formula formulatype="inline"><tex>${\rm J}_{\rm e}$</tex></formula> and n value than a corresponding increase in fill-factor. Some guidelines for optimization of conductor design are developed. </para>