Description: This Phase II program will develop a much higher operating temperature superconducting coil and deliver a full-scale prototype that establishes the capability of exceeding the requirements set forth in topic area S.109 for Sub-Kelvin Cooling ADR (Adiabatic Demagnetization Refrigeration). Specifically, the coil will generate a ramped magnetic field of 4T at or above temperatures of 15 K. It will utilize a new first-its-kind small diameter wire based on the Bi2212 high temperature superconductor (HTS), that is now developed and proven by the Phase I program to meet diameter, transport current and loss properties required for ADR coils, and with its fabrication being amenable to scale up. This wire of < 0.16 mm diameter exhibits 3 times higher current density than standard 1 mm diameter wires. Its design includes axial twisting and unmerged filaments for reducing ramped field loss, thin insulation, and current density to meet specifications for up to 20K operation at 4T field, as required for next level ADR coil advances. In this Phase II program, fabrication techniques for up to 5 km piece lengths will be established, with the Bi2212 ceramic superconductor in its unreacted form during coil winding followed by in situ reaction into its high Jc form. A full length, full radial build prototype demo coil will be designed, developed, built, tested and delivered to NASA for evaluation and validation, attaining a TRL of 8 upon completion. This wire type is also applicable to Actuators and Other Cryogenic Devices that are described in the NASA topic area, as well as in other important ramped and ac field coil types, for example in all-superconducting much lighter-weight wind generators and higher powder density motors.

Benefits: - A new type of 2212-based superconducting coil that will operate in the 15 K to 20 K temperature range for application in next generation ADR magnets sought by NASA for a class of space-based instruments, as compared to present 10 K and lower operating temperature coils, and meeting the specified > 15 K operating temperature range. - Compact high power density actuator coils in a variety of instruments.

Potential applications of this wire type include (as wire and cable): - Compact coils in instruments now using permanent magnets that have limited functionality because they cannot be turned off. - Stators in all-superconducting wind generators and high power density motors being developed to operate above 30 K in affordable cooling regimes. - Ramped central solenoid coils in fusion reactors.