19th Technical Meeting on Energetic Particles in Magnetic Confinement Systems

Resonant mode-particle interaction priors for energetic particle phase-space tomography

Not scheduled

25m

Beaulieu Congress and Exhibition Center (Lausanne, Switzerland)

Poster EPs in stellarators and 3D configurations I EP in stellarators and 3D configurations

Speaker

Mads Rud Larsen (École Polytechnique Fédérale de Lausanne)

Description

A thorough understanding of the resonant interactions between fast
ions and plasma instabilities is vital for the successful operation of burning plasmas in future devices, such as ITER. It is well described that fast ions can drive instabilities, causing confinement degradation or, alternatively, turbulence suppression [1]. Measuring the fast-ion distribution function from experimental data is thus necessary for a complete understanding of the physics. However, this requires solving an ill-posed inverse problem. The resonant interactions between waves and fast ions, as well as fast-ion stability analyses, are conveniently described in terms of three invariants of motion, energy, toroidal canonical angular momentum, and magnetic moment, which renders three-dimensional reconstructions of the fast-ion distribution function highly beneficial. This in turn requires large quantities of data, of which we have a limited amount. Therefore, to facilitate the 3D reconstructions, sophisticated physics-informed priors must be developed to address the ill-posedness of the inverse problem. In this talk, we will describe recent work on 3D Bayesian inversions of fast-ion distribution functions
in constants-of-motion phase space from FIDA data on TCV, and we will compare the reconstruction quality using different priors. This includes a newly developed resonant mode-particle interaction prior based on the kick model [2–6], which builds upon recent work on incorporating radio-frequency wave heating as prior [7,8]. The use case adopted to test the methods is that of fast-ion-driven fishbone modes in the TCV tokamak.

[1] Salewski M. et al 2025 Nuclear Fusion 65 043002
[2] Podestà M., Gorelenkova M. and White R. B. 2014 Plasma Physics and Controlled Fusion 56 055003
[3] Podestà M., Gorelenkova M., Gorelenkov N. N. and White R. B. 2017 Plasma Physics and Controlled Fusion 59 095008
[4] Podestà M. et al 2019 Nuclear Fusion 59 106013
[5] Podestà M. et al 2021 Plasma Physics and Controlled Fusion 64 025002
[6] Podestà M. et al 2022 Nuclear Fusion 62 126047
[7] Rud M. et al 2025 Nuclear Fusion 65 056008
[8] Rud M. et al 2025 Nuclear Fusion 65 112006