The Reversed Field Pinch: Understanding and Improving Confinement

The reversed field pinch (RFP) is a toroidal, high beta plasma confinement configuration with great potential as an attractive, compact, high power density fusion reactor core. Relatively poor confinement has been a main obstacle in establishing the viability of the RFP. Recent progress in understanding magnetic-fluctuation-induced transport in the RFP has spawned the idea of current profile control to reduce fluctuations and transport. With the addition of inductive poloidal current drive in the Madison Symmetric Torus (MST) device, the energy confinement time is increased five-fold from 1.2 ms to 6 ms. The lowest magnetic fluctuation level and highest electron temperature observed in MST are also obtained with inductive current profile control. These results strongly encourage the development of improved and steady-state current profile control.