High Strength Silver Sheath for Bi2212/Ag Conductor

This proposal describes an innovative high strength silver alloy for use in making Bi2212/Ag round wire conductor. Bi2212 is a high field superconductor that has the highest Jc of any practical superconductor at fields above 20 T. NbTi and Nb3Sn, which are currently the primary materials currently used for high field magnets, are limited to about 10.5 T and 18 T respectively. To generate magnetic fields greater than 20 T, a new high field conductor such as Bi2212 is needed. However, Bi2212 is brittle compound that can be easily damaged, and its critical current is very strain sensitive. The Bi2212 compound is contained in a silver matrix in the wire. The silver matrix is chemically compatible with the Bi2212 ceramic, and it aids in processing the conductor. However, silver is a low strength, low stiffness material. It provides little in the way of mechanical support for the conductor during either magnet fabrication or operation. High field magnets are subject to large stresses. These stresses can exceed the yield strength of the silver matrix, causing degradation of conductor thus limiting the usefulness of Bi2212 for high field magnets resulting in the need to use more costly approaches for producing high magnetic fields. This proposal seeks to develop a high strength, high modulus silver alloy for manufacturing Bi2212 round wire multifilament conductor. The silver is strengthened by a fine dispersion of Al2O3 particles producing an alloy having high strength and stiffness. The Al2O3 particles are chemically inert to Bi2212, and strengthen the silver matrix even after high temperature processing. The increased strength and stiffness provided by the silver alloy results in greater resistance to mechanical stresses and electromagnetic forces. These attributes provide for less complex magnet design, resulting in reduced costs with the benefit of higher performance. Potential applications include particle accelerators and high field NMR magnets. Commercial applications and other benefits: A high field superconductor such as Bi2212 will find its primary application in accelerator magnets for high energy physics. The other major application for the technology is high field nuclear magnetic resonance systems for imaging complex organic compounds and biological materials