19th Technical Meeting on Energetic Particles in Magnetic Confinement Systems

Session

EP in stellarators and 3D configurations

29 Sept 2026, 09:00

Beaulieu Congress and Exhibition Center (Lausanne, Switzerland)

36. Energetic particle instability characteristics of reactor-scale stellarators

Don Spong (Oak Ridge National Laboratory)

29/09/2026, 09:00

EP diagnostics and analysis methods

Invited

Recently stellarators have made significant progress with respect to improvements in the classical guiding center energetic particle confinement via shape optimization [1]. However, as has been observed with tokamaks once the neoclassical confinement is reduced to a low level, the confinement properties of energetic particle (EP) populations may be more dominated by instability-induced...

19. Effects of Pressure Gradients of Multiple Fast-Ion Species on Fast-Ion-Driven Instabilities in the Large Helical Device

Ryosuke SEKI (National Institute for Fusion Science)

29/09/2026, 09:35

EP diagnostics and analysis methods

Oral

In magnetic confinement fusion devices, there are multiple fast-ion species such as fusion product (i.e., α particles) and fast deuterons produced by neutral beam injection. These fast ions may induce MHD instabilities such as Alfvén Eigenmodes (AEs) which can enhance fast-ion transport and losses. The study of fast-ion-driven MHD instabilities is one of the important topics for fusion...

32. Properties of Magnetohydrodynamics Instabilities in ITER-Scale Helical Core Plasmas

Dr Panith Adulsiriswad (adulsiriswad.panith@qst.go.jp)

29/09/2026, 10:00

EP diagnostics and analysis methods

Oral

The tokamak hybrid scenario is a candidate for long-pulse, sawtooth-free operation in ITER. This sawtooth-free state is attributed to its robust, near-flat q≳1 core safety factor profile, maintained by the long-lived MHD-driven current redistribution that hinders the peak current profile. A notable example is the long-lived m/n=1/1 quasi-interchange mode. However, this m/n=1/1 mode leads to...

70. Resonant plateau collisional passing alpha losses

Miguel Calvo Carrera (Massachusetts Institute of Technology)

29/09/2026, 10:25

Poster session I

Poster

Alpha particles typically exhibit collisionless dynamics throughout most of their phase space. However, their motion can be very sensitive to collisions under resonant conditions. The collision operator is required to resolve the singular behavior around resonances, allowing the formation of a collisional boundary layer, where a perturbed distribution function forms and drives radial...

35. Finite Larmor radius effects in stellarators – the hidden ripple inside hidden symmetry

Michael Fitzgerald (UKAEA)

01/10/2026, 16:15

EPs in stellarators and 3D configurations II

Invited

It has long been understood that alpha particle equilibrium in tokamaks relies on the existence of approximate symmetries in time, gyroangle and toroidal angle. Violation of these symmetries in tokamaks leads to energetic particle losses observed in simulation and experiment. This behaviour is well modelled in terms of collisionless particle trajectories.
In stellarators, a chief concern for...

17. Energetic particle transport induced during core density collapses in LHD and Stellarator reactor relevant configurations

Jacobo Varela Rodriguez (Institute for Fusion Studies UT-austin)

01/10/2026, 16:50

EPs in stellarators and 3D configurations II

Invited

Core density collapses (CDC) events observed in the Large Helical Device (LHD) are a major concern for the performance of future Stellarator reactors, particularly for quasi-symmetric magnetic field configurations with weak magnetic shear. CDC severely restrict the maximum β of LHD outward shifted magnetic axis configurations, strongly fueled by pellets and heated by neutral beam injector...

77. Suppression of Coherent Energetic Particle Phase Space Structures due to 3D fields

Alexandra Lachmann (Columbia University)

01/10/2026, 17:25

EPs in stellarators and 3D configurations II

Oral

Modulations in amplitude and phase of Alfvénic eigenmodes (AEs) may occur due to wave particle interactions with energetic particle (EP) distribution functions [1]. Damping can shrink the resonance with the mode, creating a hole-clump pair in the region of the shrunken resonance [1]. Hole-clump pairs in phase space are associated with phase modulations (chirps) of modes and propagate through...

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

Mads Rud Larsen (École Polytechnique Fédérale de Lausanne)

EPs in stellarators and 3D configurations I

Poster

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...