First measurements of velocity-space resolved intra-ELM fast-ion losses on the TCV tokamak

First measurements of velocity-space resolved intra-ELM fast-ion losses on the TCV tokamak

Edge Localised Modes (ELMs) induced fast-ion losses have been characterised in the energy, E , and pitch, $\lambda = v_\parallel/v$ , space using a unique Fast Ion Loss Detector (FILD) on the tokamak à configuration variable. The FILD is equipped with a 128 Avalanche Photo Diodes (APDs) camera measu...

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Bibliographic Details
Main Authors: J. Poley-Sanjuán, A. Jansen Van Vuuren, J. Galdón-Quiroga, S. Mazzi, M. Podestà, M.B. Dreval, B.P. Duval, A. Fasoli, A.N. Karpushov, B. Labit, U. Kumar, the EUROfusion Tokamak Exploitation Team, the TCV Team
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:Nuclear Fusion
Subjects:
fast particles
FILD
ELMs
microsecond velocity-space
acceleration
Online Access:https://doi.org/10.1088/1741-4326/adf95b
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Summary:Edge Localised Modes (ELMs) induced fast-ion losses have been characterised in the energy, E , and pitch, $\lambda = v_\parallel/v$ , space using a unique Fast Ion Loss Detector (FILD) on the tokamak à configuration variable. The FILD is equipped with a 128 Avalanche Photo Diodes (APDs) camera measuring scintillator emission with a 1 MHz bandwidth. The well-defined view lines of the APDs allow for obtaining velocity space information from the emission pattern with unprecedented temporal resolution. Making use of the enhanced FILD capabilities, ELM-induced fast-ion losses were investigated in the ITER Baseline Scenario, mimicking its shape and normalised plasma parameters. Significant fast-ion losses were observed, notably before and during the ELM crashes induced by the presence of a 2/1 MHD instability localised at the plasma’s normalised radius, $\rho \sim 0.7$ . The fast-ion interaction with the plasma instability is concluded to be unconnected to the presence of the ELMs. During the ELM crashes, there is an observed spread in both the fast-ion pitch and energy that reaches higher values (∼ 70 keV) than expected from the pre-ELM fast-ion population, generated by Neutral Beam Injection at ∼27 keV. This implies a fast-ion acceleration during the ELM’s crash. Full orbit neoclassical simulations are used to calculate the neoclassical fast-ion velocity space lost to the FILD and to quantify the neoclassical fast-ion losses.
ISSN:0029-5515

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