Reversed Field Pinches are toroidal plasma confinement devices.
The Reversed Field Pinch (RFP) concept is a design very much like tokamaks but the device uses the electromagnetic properties of the plasma itself to generate the confining magnetic fields. RFP systems are being studied for possible low magnetic field, high plasma density confinement designs and to enhance understanding of the physics of toroidal confinement in operating regions that are outside the range of standard tokamak devices.
The RFX device
© Image: ENEA
The RFP is an axisymmetric toroidal system in which the plasma is confined by a combination of a poloidal field produced by the plasma current flowing around the torus, and a toroidal field produced by currents flowing both in the plasma and in external coils. Schematically, the system is similar to a tokamak and consists of a toroidal vessel, in which the plasma is formed, surrounded by a toroidal winding that generates the initial toroidal field, and coupled to a coaxial transformer whose secondary winding is the plasma current. The configuration gets its name from the fact that the toroidal magnetic field in the outer region is reversed with respect to its direction on the axis of the machine.
There are two RFP devices in the EU, RFX in Italy and EXTRAP T2 in Sweden which contribute to studies on achieving high-performance operation and controlling plasma modes.