Upgrades of the RFX-mod experiment

RFX-mod is a toroidal device (R/a=2m/0.46m, [Sonato 2003]) characterised by great reliability and flexibility which allows performing experiments in a wide range of safety factor values q(a)=aBt/RBp values. As a Reversed Field Pinch it demonstrated stable operations for discharge times longer than the surrounding stabilizing shell time, thanks to the feedback control of Resistive Wall Modes [Paccagnella2007] and Tearing Modes [Zanca2007]. As a low toroidal field (0.6T) high aspect ratio circular ohmic Tokamak, RFX-mod proved routine operations in the very low q regime (i.e. q(a) <2) [Zanca2012] and with the insertion of a polarized electrode it also obtained access to H-mode [Zuin2017]. Based on the understanding of the interaction between the MHD instabilities and the RFX-mod load assembly (vacuum vessel, stainless steel supporting structure and copper stabilizing shell) some enhancements of the device have been proposed and are now in a design phase [Peruzzo2016]. These can be summarized as: 1) upgrade of the magnetic front-end to reduce the amplitude of MHD instabilities, thus improving plasma performance thanks to a mitigated plasma-wall interaction; 2) change of the Plasma Facing Material and upgrade of the wall conditioning system to improve the plasma density control; 3) installation of a 1MW neutral beam to robustly achieve H-mode without the inserted electrode during tokamak operations; 4) upgrade of the diagnostics in order to improve the control and understanding of plasma behavior. This contribution will describe the scientific motivations of the proposed upgrades and will summarize the status of the design.