Abstract
The recent progress in high-beta reversed-fieldpinch (RFP) studies is reviewed. Experimental efforts to suppress the RPF dynamo modes (core resonant tearing modes) have resulted in remarkable confinement improvement in large RFP experiments. The poloidal beta (≈total beta) value of ˜20% has been achieved with improved confinement. After suppressing the current-driven modes, the role of pressure-driven modes will become important in the RFP dynamics. Theoretical studies of pressure-driven modes have revealed that ideal-mode-stable RFP configurations with βP≈30% exist, and that unstable mode spectra are sensitive to local current profiles as well as to pressure profiles. The role of the Suydam criterion on the stability of ideal modes is discussed briefly. From an experimental point of view, it is essential to investigate the beta limit in the RFP by increasing heating power density under conditions of improved confinement.
