Speaker
Description
The plasma edge plays a key role in determining confinement and stability in fusion devices, governing heat and particle transport to plasma-facing components. Reliable, high-resolution diagnostics are therefore essential to characterize edge plasma properties and their dynamics.
A comprehensive set of spectroscopic diagnostics has been successfully developed and implemented to investigate plasma–wall interaction and light-impurity behavior at the edge of the RFX-mod2 device. The Light Impurity Tomography (LIT) system was designed, realized, assembled, and calibrated, providing a flexible tomographic tool for measuring the spatial emissivity distribution of Hα radiation and light impurities. The system consists of seven cameras distributed along the full poloidal cross-section, enabling both radial and poloidal resolution of particle influxes from the first wall and allowing detailed studies of the interaction between particle sources and the three-dimensional magnetic field structure.
In parallel, the MANTIS spectroscopic diagnostic was developed to obtain two-dimensional, wavelength-resolved images of edge plasma emission. The optical design and realization of a dedicated polychromator, combined with in-vessel mirrors and coherent fiber bundles, enabled tangential viewing of the plasma edge. The polychromator architecture, based on concave mirrors, lenses, and interferential filters, allows the simultaneous detection of emissions from different impurity species using multiple cameras. Laboratory assembly, alignment, and testing confirmed the diagnostic performance and spatial resolution.
A key outcome of these diagnostics is their capability to support three-dimensional reconstructions of edge plasma emissivity. Such 3D reconstructions are particularly crucial in devices like RFX-mod2, where intrinsically three-dimensional magnetic configurations and perturbations strongly influence plasma–wall interaction and impurity transport. The combined use of tomographic and spectroscopic imaging enables a more realistic representation of the edge plasma, improving the interpretation of impurity sources, transport mechanisms, and their coupling with complex magnetic topologies.
Together, the LIT and MANTIS diagnostics provide complementary and spatially resolved measurements of main gas and impurity influxes, delivering advanced experimental tools to assess the role of three-dimensional effects on plasma–wall interaction and impurity control in fusion plasmas.