Insulation Materials and Methods for Bi2212 Magnets

This proposal concerns an investigation of methods and materials for insulating Bi2212 conductor for manufacturing high field magnets. Bi2212 is a high field superconductor that has the highest Jc of any practical superconductor at fields above 15 T. NbTi and Nb3Sn which are the primary materials currently used for high field magnets are limited to magnetic field generation of about 10.5 T and 20 T respectively. To generate magnetic fields greater than 20 T, a new high field conductor such as Bi2212 is needed. However, Bi2212 is a highly reactive compound and must be heat treated in oxygen at temperatures in the range of 890 °C. Currently used insulating materials tend to react with silver and Bi2212 at these temperatures degrading the magnet performance of even causing the loss of the magnet. This proposal seeks to develop an improved insulating material and method for manufacturing Bi2212 magnets. It will develop a method for insulating Bi2212 wire and determining the process conditions that optimize manufacturing magnets from this insulated conductor. Potential applications include particle accelerator and high field NMR magnets. The factors leading to leakage during heat treatment of Bi2212/Ag superconductors were investigated. It was found that the material used for insulating the wire reacted with the silver sheath of the conductor causing the formations of pits, which lead to leakage and degradation of conductor Ic. Several alternate insulation schemes were evaluated for their effect in reducing the reaction with the silver sheath. The Phase II project will encompass developing an alternate approach to insulating Bi2212/Ag conductor with materials that are non reactive with silver, and developing the processing conditions for making coils from this material that meets the requirement for HEP applications. Commercial Applications and other Benefits as described by the awardee: 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.