Accelerator Technologies for Present and Future Accelerator Facilities, Advanced Sources for Accelerators

Nb3Sn superconducting wire is a preferred superconducting medium for certain applications because of the high field it can produce. Nb3Sn-based wire must be reacted at >600 ºC in an inert environment before use, and the wire¿s insulation also must be heated and remain intact throughout this reaction. Because the reacted wire is too brittle to wind, the wire, with its insulation, is first wound around a mandrel and then reacted. However, the existing fiberglass insulation sheaths are relatively thick, taking valuable space in the wound configuration ¿ space that could be better occupied with superconductor. Moreover, the possible looseness of the insulator around the superconductor wire makes uniform, well-packed winding difficult. This project will develop a new insulation concept for Nb3Sn superconductors: a thin (<30 micron) ceramic-based coating that not only can be wound but also can survive the wire¿s reaction cycle. The thin ceramic insulation will adhere to the wire and form a more stable and controllable base for precision winding compared to typical fiberglass insulation, which adds about 130 microns to the wire diameter. The improvement in packing factor could be as much as 35 to 45%. During Phase I, a flexible coating was applied from a prototype production coating unit capable of depositing the coating in a single pass. Segments of short Nb3Sn wire (<100 m) and long surrogate copper wire (>500 m) were coated to demonstrate coating capability and scalability. In Phase II, the insulation coating will be optimized, the coating unit will be improved, and the resulting wire/insulation product will be tested for superconductivity and other properties. Commercial Applications and Other Benefits as described by the awardee: The initial market for the proposed insulated Nb3Sn wire is for a superconducting undulator at a national laboratory, since a laboratory¿s verification will be necessary to generate further interest. This additional interest would come from other national laboratories and from related laboratories in Sweden, Germany, Italy, the UK, Canada, Taiwan, France, and Japan. Even if only a few of these opportunities came to fruition, demand for significant kilometers of insulated wire can be imagined. Commercial opportunities include the superconducting magnets that currently are used in medical instruments and industrial processing.