New Highly Radiation-Resistant Insulation Process for High Field Accelerator Magnets

High-field accelerator magnets based on niobium-tin superconductor technology are planned for use in several U.S. high energy physics programs. The use of these materials requires a high-temperature process to complete the production of the coil. As part of the process, a ceramic insulating layer is added to the superconductor. However, the currently available ceramic insulation is produced in tape form, which causes an increased-thickness buildup within the insulation layer. Braided ceramic insulation, which is stable at the superconductor processing temperatures, could provide a thin radiation-resistant insulation if it could be co-processed with the superconductor at elevated temperatures. This project will develop a method for braiding ceramic fibers directly onto superconducting cables to produce a thin ceramic-based insulation that is both radiation resistant and stable at the superconducting processing temperatures of 600 to 700°C. In Phase I, a process for braiding ceramic fibers directly onto continuous lengths of conductor cables was demonstrated. Insulation thicknesses on the order of 0.2 mm were measured via optical microscopy, and insulation performance was assessed through mechanical and thermal testing. Phase II will continue the development and optimization of the high-strength, braided ceramic insulation. The process will be scaled-up to levels suitable for industrial magnet fabrication. Insulated superconductor cables will be delivered to the Department of Energy at the conclusion of Phase II. Commercial Applications and other Benefits as described by the awardee: The thin ceramic-based insulation would provide magnet developers with a means of producing densely packed superconductor coils, using a high-temperature wind-and-react process. This processing technology should simplify magnet production, lower fabrication costs, and allow for higher operating fields. Applications such as high field magnets, fusion magnets, and medical MRI instruments would become more viable, with improved magnet processing, higher strength, and improved reliability. Higher efficiency transformers that are resistant to heat damage also would become viable