Micro-Turbulence in Reversed-Field Pinch Plasmas with Improved Confinement Due to Current Drive

Reversed-field pinches (RFPs) have a unique magnetic field configuration: the strength of the poloidal field is comparable to that of the toroidal field, and the direction of the toroidal field reverses its sign as one moves from the core to the edge. In standard RFP discharges, multiple tearing modes are destabilized on closely-spaced rational surfaces that overlap, creating stochastic magnetic fields. However, by utilizing an inductive current profile control technique called pulsed poloidal current drive (PPCD), the tearing modes can be stabilized, and largely-intact nested flux surfaces can be sustained in an RFP. In such plasmas, micro-turbulence plays an important role in transport, similar to tokamaks and optimized stellarators, and thus micro-instabilities and their nonlinear behavior require study in this less-explored parameter regime. This article reviews both theoretical and experimental investigations of micro-turbulence in RFP discharges with the application of PPCD. https://www.jspf.or.jp/Journal/PDF_JSPF/jspf2026_05/jspf2026_05-en.pdf