Phase space resolved measurements of fast-ion density fluctuations and energy transfer induced by Alfvén eigenmodes

Jose Rueda-Rueda; Xiaodi Du; William W Heidbrink; Gregory G Howes; Pablo Oyola; Tommaso Barberis; Deyong Liu; Michael A Van Zeeland; Filipp Khabanov; Kyle Callahan

doi:10.1088/1741-4326/aeac6a

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Phase space resolved measurements of fast-ion density fluctuations and energy transfer induced by Alfvén eigenmodes

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Phase space resolved measurements of fast-ion density fluctuations and energy transfer induced by Alfvén eigenmodes

Jose Rueda-Rueda, Xiaodi Du, William W Heidbrink, Gregory G Howes, Pablo Oyola, Tommaso Barberis, Deyong Liu, Michael A Van Zeeland, Filipp Khabanov and Kyle Callahan

Nuclear fusion, Vol.66(12), 126044

10/07/2026

DOI: 10.1088/1741-4326/aeac6a

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Abstract

We present phase-space resolved measurements of energetic particle (EP) fluctuations near Toroidal Alfvén Eigenmode (TAE) frequencies in the DIII-D tokamak. A newly rebuilt fast channel in the Imaging Neutral Particle Analyzer (INPA) system, with a significantly improved signal-to-noise ratio, enabled the detection of fluctuations at approximately 100-130 kHz, frequencies that were previously inaccessible. Coherent fluctuations with amplitudes of about 1\% were observed in localized regions of EP phase space. The secular energy exchange rate between the wave and the EP population is directly extracted from the observed INPA and electron density and temperature fluctuations, accounting for both parallel and perpendicular electric field components. Analysis reveals that poloidal energy exchange dominates by approximately two orders of magnitude over parallel and radial components, with energy transfer occurring through the interaction between drift velocities and perpendicular electric fields. The averaged energy exchange rates are of the order of 10 keV/s. A comparison with ASCOT orbit-following simulations confirms that the observed fluctuations originate from the passively viewed (trapped) particle population rather than from passing particles. The measured TAE radial structure shows good agreement with ideal MHD simulations using the NOVA code. These measurements provide unprecedented experimental validation of wave-particle energy transfer mechanisms.

energetic particles

INPA

Energy Exchange

DIII-D

Details

Title: Subtitle: Phase space resolved measurements of fast-ion density fluctuations and energy transfer induced by Alfvén eigenmodes
Creators: Jose Rueda-Rueda - University of California, Irvine
Xiaodi Du - General Atomics (United States)
William W Heidbrink - University of California, Irvine
Gregory G Howes - University of Iowa
Pablo Oyola - Princeton Plasma Physics Laboratory
Tommaso Barberis - Princeton Plasma Physics Laboratory
Deyong Liu - General Atomics (United States)
Michael A Van Zeeland - General Atomics (United States)
Filipp Khabanov
Kyle Callahan - University of California, Irvine
Resource Type: Journal article
Publication Details: Nuclear fusion, Vol.66(12), 126044
DOI: 10.1088/1741-4326/aeac6a
ISSN: 0029-5515
eISSN: 1741-4326
Publisher: IOP
Grant note: Department of Energy: DE-FC02-04ER54698 DOE: DE- AC02-09CH11466, DE-SC0014664, DE-SC0020337, DE-SC0026430
The author would like to thank the technical staff at DIII-D, and in particular the diagnostic team, for their help installing the EP diagnostics upgrade.
Language: English
Date published: 10/07/2026
Academic Unit: Physics and Astronomy
Record Identifier: 9985241830102771

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