Description: This proposal focuses on the superconducting coils subsystem, a critical subsystem for the PFRC reactor and Direct Fusion Drive and other fusion and electric propulsion technologies. Our strategy for PFRC has evolved since our Phase I proposal, and we now propose a hybrid magnet approach: a combination of so-called “dry” conduction-cooled low-temperature (LTS) superconductor magnets and high-temperature (HTS) magnets that are operated at low temperature for maximum current at high fields. Conduction-cooled LTS magnets are becoming state-of-the-art for MRI machines, and reduce coolant requirements from 1000’s of liters of helium over the lifetime of the machine to a few liters in a closed cryocooler. This is with a mass penalty for cooling of only about 5%. These low-coolant LTS magnets, producing a field of 5 to 6 T, will have excellent safety margin in both critical current and field and will have a clear path to space applications. PFRC also requires higher-field nozzle magnets producing fields of 20 to 30 T. These would utilize HTS superconductors operated at low temperatures of about 10 K. All coils will require highly efficient cooling systems, excellent mechanical support, and overall low mass including structural components. Our partner, PPPL, is the only institution in the world where active research on the physics and technology of small, steady-state fusion devices is being performed. We propose a Phase II experiment to build a 0.5 Tesla LTS magnet with a split pair of winding packs, to mimic a subset of the PFRC magnets. A separate pulsed copper test coil to simulation the plasma will be used to study the effects on the magnet of FRC formation, which will occur in a fraction of a second and result in large increases in magnetic field at the windings. In parallel, we will continue to advance the design of the HTS nozzle magnets, seeking the lowest mass solution.

Benefits: A small fusion engine such as Direct Fusion Drive would be useful for many deep- and inner-space missions, such as Lagrange points, manned Mars and lunar missions, a Pluto orbiter and lander, and the 550 AU solar gravitational lens. The novel superconducting coils have applications to additional advanced propulsion concepts and scientific payloads. One example is the AMS-02 experiment for which a low-temperature superconducting coil option was built and tested but later swapped out for a traditional magnet with a longer lifetime. Other advanced propulsion techniques require superconducting coils including the VASIMR electric thruster and the PuFF fission-fusion thruster. There has been considerable research on using superconducting coils for radiation shielding; these coils may also be useful for space materials processing and precision formation flying.

There are many military and civil applications of the fusion engine and the coils. Military space applications include high-power Earth satellites with radar, laser, or communications payloads. There are wider applications including generators for wind turbines, high efficiency motors, particle accelerators, energy storage, and terrestrial fusion reactors. Small terrestrial fusion reactors of the PFRC type have unique application to remote and mobile applications, such as military forward power and disaster relief, as well as high-intensity energy applications like desalination. This project would contribute greatly to this wider body of work.