field-reversed configuration (FRC) is a compact 📝plasma confinement concept whose magnetic fields close on themselves without a central hole, holding an elongated ring of plasma inside a simple cylindrical vessel.
Its defining contrast is with the 📝Tokamak: where a tokamak threads the center of its plasma torus with a solenoid and 📝toroidal field coils, an FRC has no material at its center at all. The confining field is generated almost entirely by current flowing in the plasma itself, which reverses an externally applied field — hence the name — and closes it into nested loops. Together with the spheromak, the FRC belongs to the family of self-organized plasmas called compact toroids.
The concept's appeal is 📝plasma beta near one: plasma pressure roughly equal to magnetic pressure, an order of magnitude more efficient use of the field than a conventional tokamak achieves, packaged in a linear geometry that simplifies construction and maintenance. Its historic weakness is holding that state — FRCs long lasted only fractions of a millisecond, and their stability and confinement at reactor scale remain the open questions. The configuration anchors several private ventures: TAE Technologies sustains FRCs with neutral beams, Helion accelerates and compresses colliding FRCs, and FRCs serve as the target plasma in 📝magnetized target fusion.