Energy confinement and future reversed field pinches

Energy confinement within the reversed field pinch (RFP) is governed by three plasma regions: a poorly confined plasma core characterized by parallel (radial) transport and flux surfaces destroyed by m=1 tearing mode activity associated with dynamo relaxation; a medium confined edge limited by ideal pressure gradient driven modes; and a good confinement region located near the reversal layer. The good confinement region determines the global confinement characteristics of the RFP, and, if limited by resistive interchange modes, would be consistent with the Connor-Taylor scaling that has provided a good fit to international RFP results. After establishing a two parameter fit of confinement scaling to the RFP database, the scaling relation is used to project the physical characteristics of, and costs associated with, next step and ignition experiments for ohmically heated RFPs. The RFP projects to smaller and less expensive machines than the tokamak with comparable performance