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Description
RFX-mod2 is the upgraded version of the RFX-mod experiment, a toroidal plasma confinement device, with a major radius of 2 m and a minor radius of 0.5 m, capable of operating in both Reversed Field Pinch and Tokamak configurations. RFX-mod2 is presently under re-assembly at Consorzio RFX (Padova, Italy) after substantial modifications aimed at increasing the plasma volume and optimizing its position with respect to the active and passive components of the Magnetohydrodynamic (MHD) control system, enabling the exploration of plasma regimes with higher temperature and improved stability. As in all magnetic confinement devices, the initial operational phase requires
effective first wall conditioning, typically performed by Glow Discharge
Cleaning (GDC). The GDC system of RFX-mod2 has been significantly upgraded
and now includes eight new fixed electrodes, which will act as Plasma
Facing Components (PFCs), together with two movable electrodes designed
for the boronization procedure. The new configuration is intended to improve
plasma uniformity and enhance the overall efficiency of the wall conditioning
process.
This work presents the first experimental results obtained during hydrogen
and helium discharges using the new fixed electrodes. Experimental
campaigns have been carried out in a dedicated facility where representative
first wall materials for RFX-mod2 — including alumina-coated copper
components, graphite tiles, and Torlon 5030 support rings — are installed.
Plasma temperature and density measurements have been performed as a
function of probe position and electrode feeding power. In addition, Residual
Gas Analysis (RGA) and optical spectroscopy diagnostics have been used to assess the effectiveness of the GDC process.
The results provide key information on the operational reliability and
conditioning performance of the upgraded GDC system, contributing to the
optimization of future RFX-mod2 plasma-wall conditioning campaigns.