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Description
An in-vessel radio-frequency (RF) antenna installed at the Tokamak à Configuration Variable (TCV) has been employed over the past few years to probe electromagnetic fluctuations associated with Runaway Electron (RE)-driven instabilities, covering the broad spectrum of RE scenarios achievable in the TCV plasma. In this work, a first interpretative analysis of the measured wave activity is performed. The signals exhibit coherent spectral structures, featuring discrete frequency spacings and evolving frequency branches throughout the plasma discharge. These features show preliminary agreement with expectations from a hot plasma description, suggesting a possible interpretation of the coupled plasma modes in terms of ion Bernstein waves (IBW), confirming previous observation already performed at FTU [1]. A second part of the work presents the final design of a compact multi-loop antenna, developed from a systematic exploration of candidate configurations. The new design should achieve more uniform sensitivity across the hundreds-of-MHz frequency range typical of the TCV plasma instabilities, while respecting the port geometrical constraints. Such an enhanced sensitivity is expected to enable a more accurate characterization of the instability frequency dependence relative to relevant plasma parameters.
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.
[1] C. Castaldo et al., Nucl. Fusion 64 086003 (2024)