A toroidal confinement concept in which the toroidal magnetic field reverses direction near the plasma edge — achieving high beta and high current but struggling with turbulent transport.
A reversed-field pinch (RFP) is a toroidal magnetic confinement device in which the toroidal magnetic field reverses sign at the plasma edge. Unlike a tokamak (where the toroidal field is much stronger than the poloidal field), an RFP operates with comparable toroidal and poloidal fields, and the toroidal field at the wall points in the opposite direction from the core.[1]
RFPs operate at much higher plasma beta (~20%) than tokamaks and require much weaker external magnets (the field at the wall is comparable to the poloidal field). The high plasma current provides strong ohmic heating, potentially reaching fusion temperatures without auxiliary heating.[2]
The dynamo turbulence that sustains the RFP configuration also causes poor energy confinement, typically 5–10 times worse than a tokamak of the same size. Experiments at RFX-mod (Italy) and MST (Wisconsin) have demonstrated improved confinement in states with reduced magnetic chaos, but RFPs remain a secondary research line.[3]