Field-Reversed Configuration

A field reversed configuration, or FRC, is a plasma device studied as a route to nuclear fusion that confines its plasma on closed magnetic field lines with no central penetrating structure, shaping the plasma into a self stable torus resembling a smoke ring; a toroidal electric current running through the cylindrical plasma creates a poloidal magnetic field that reverses relative to an externally applied field, producing what is called a high beta axisymmetric compact toroid that confines itself without the complex external coils a tokamak or stellarator requires. The configuration was first observed in the laboratory in the late 1950s during theta pinch experiments with reversed magnetic fields, was studied through the 1960s and 1970s especially at the United States Naval Research Laboratory, and received extensive further research from 1975 to 1990 under Project Sherwood at Los Alamos National Laboratory; interest resurged from the 1990s onward, and as of 2019 the field reversed configuration remained an active research area. Unlike the related spheromak, an FRC has almost no toroidal magnetic field component and carries little magnetic helicity, giving it a beta value near 1 compared with roughly 0.1 for a spheromak, a property that makes it potentially attractive for a future fusion reactor.