Overview of the RFX-mod fusion science activity

This paper reports the main recent results of the RFX-mod fusion science activity. The RFX-mod device is characterized by a unique exibility in terms of accessible magnetic con gurations. Axisymmetric and helically shaped reversed- eld pinch equilibria have been studied, along with tokamak plasmas in a wide range of q(a) regimes (spanning from 4 down to 1.2 values). The full range of magnetic con gurations in between the two, the so-called ultra-low q ones, has been explored, with the aim of studying speci c physical issues common to all equilibria, such as, for example, the density limit phenomenon. The powerful RFX-mod feedback control system has been exploited for MHD control, which allowed us to extend the range of experimental parameters, as well as to induce speci c magnetic perturbations for the study of 3D effects. In particular, transport, edge and isotope effects in 3D equilibria have been investigated, along with runaway mitigations through induced magnetic perturbations. The rst transitions to an improved con nement scenario in circular and D-shaped tokamak plasmas have been obtained thanks to an active modi cation of the edge electric eld through a polarized electrode. The experiments are supported by intense modeling with 3D MHD, gyrokinetic, guiding center and transport codes. Proposed modi cations to the RFX-mod device, which will enable further contributions to the solution of key issues in the roadmap to ITER and DEMO, are also brie y presented.