H-Mode Achievement and Edge Features in RFX-Mod Tokamak Operation

The RFX-mod experiment is a fusion device designed to operate as a Reversed Field Pinch (RFP), with a major radius R= 2 m and a minor radius a = 0.459 m. Its high versatility recently allowed operating also as an ohmic tokamak allowing comparative studies between the two configurations in the same device. The device is equipped with a state of the art MHD mode feedback control system, providing a magnetic boundary effective control, by applying resonant or non-resonant magnetic perturbations (MP) both in RFP and in tokamak configurations. In the fusion community the application of MPs is widely studied as a promising tool to limit the impact of plasma filaments and ELMs on plasma facing components. An important issue is envisaged in the exploitation of the RFX-mod active control system for ELM mitigation studies. As a first step in this direction, this paper will focus on the most recent achievements in term of RFX-mod tokamak explored scenarios, which allowed the first investigation of the ohmic and edge biasing induced Hmode. Among the others the realization of D-shaped tokamak discharges and the design and deployment of an insertable polarized electrode were accomplished. Reproducible H-mode phases were obtained with insertable electrode negative biasing stimulation in plasma shaped Single Null discharges, representing an unexplored scenario with this technique. Important modification of the edge plasma density and flow properties are observed. During the achieved H-mode ELM-like (Edge Localized Modes) electromagnetic composite filamentary structures are observed. They are characterized by clear vorticity pattern and parallel current.