Bi2212 powder production with wide Tmax window for high field magnet applications

The United States Department of Energy’s Office of High Energy Physics seeks nextgeneration superconducting wire to build highfield magnets that operate in fields greater than 16 Tesla for the advancement of fundamental particle physics. Round, multifilament, superconducting wire made from bismuth strontium calcium copper oxide Bi2212 powder exhibits great promise to achieve the performance required for accelerator magnet applications. One of the challenges to large scale deployment of hightemperature superconducting technologies such as Bi2212 magnets is that the wire must undergo overpressure heat treatment to achieve the high engineering critical current values needed to achieve desired performance metrics. The performance of the Bi2212 superconducting wire is extremely sensitive to minor temperature gradients experienced during the overpressure heat treatment process. Optimization of the powder properties and fabrication parameters will enable a broader temperature window for wire processing that delivers high performance of the resultant Bi2212 wire. Building upon its expertise in the production of highperformance powders, the Small Business has developed a consistent methodology to produce Bi2212 powder that, when used to produce Bi2212 wire, demonstrates excellent performance. During Phases I and II of this project, the Small Business produced multiple batches of Bi2212 powder with variations in phase composition including dopants, particle characteristics specific surface area, and processing parameters. One Subcontractor used the powders to fabricate monocore tapes Phase I and round, multifilament wires Phase II. The tapes and wires were then subjected to overpressure heat treatment by another collaborator. The engineering critical current values were determined as a function of the temperature window for processing. Further research and development of the Bi2212 powders during a Phase IIA project will build upon the successes achieved during Phases I and II. The Small Business will continue exploration of the material phase space i.e., cation composition, as well as powder processing parameters that affect particle size and phase distribution. An additional Subcontractor will join the project in order to construct and evaluate a prototype highfield magnet using Bi2212 superconducting wires made from powders developed and produced by the Small Business. Commercial applications include stateoftheart systems for nuclear magnetic resonance NMR and magnetic resonance imaging MRI. The higher magnetic fields enabled by the newly developed Bi2212 materials will facilitate advanced precision, speed, and resolution from these instruments. Fusion energy is also a potential beneficiary from this technology.