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Aug 18

ELM suppression and confinement in negativetriangularity with stronger shaping in ASDEXUpgrade

3 days ago

Branka Vanovac, Joerg Hobirk, Andrew Oakleigh Nelson, Olivier Sauter, Mike G Dunne, Michael Faitsch, Thomas Pütterich, Rainer Fischer, Dirk Stieglitz, Erika Strumberger, et al.

Max Planck Institute for Plasma Physics, Massachusetts Institute of Technology, Columbia University, Ecole Polytechnique Federale de Lausanne

Recent experiments conducted during the 2025 campaign in ASDEX Upgrade have pushed the limits of negative triangularity shaping, achieving top triangularity values of δ top ∼-0.55 while keeping bottom triangularity around 0 in diverted plasmas. Guided by ideal-MHD stability calculations using the linear MHD BALOO solver and supported by TCV results, these experiments have demonstrated a transition to an edge that is more stable against peeling-ballooning modes, leading to ELM-free plasmas. Those ELM-free plasmas also exhibit a dithering behavior similar to limit-cycle oscillations. Linear MHD modeling showed that the achieved shapes remained marginal with respect to the second stability region for ballooning modes suggesting that with minor further shaping, a robust NT edge could be achieved. The associated energy confinement is generally reduced, with clear signs of strong power degradation. In addition, a high fraction of fast-ion energy is observed, particularly in high-power/low-density discharges. An approximately 15% improvement in normalized energy confinement is obtained when seeding nitrogen. As this effect comes from the edge, it highlights a path towards pedestal tailoring for further confinement optimization and supporting negative triangularity as a potentially viable reactor- relevant operational scenario in full-metal-wall devices.

Max Planck Institute for Plasma PhysicsSwiss Federal Institute of Technology LausanneMassachusetts Institute of Technology

3 days ago

Aug 17

The status and design challenges of the heating and current drive systems for DTT

4 days ago

Nuclear Fusion

Gustavo Granucci, Silvio Ceccuzzi, Afra Romano, Andrea Murari, Gian Luca Ravera, Piero Agostinetti, Sofia Bertolami, Falk Braunmüller, Alessandro Bruschi, Daniele Busi, et al.

Consorzio RFX, Consiglio Nazionale delle Ricerche, ENEA Agenzia Nazionale per Le Nuove Tecnologie l'Energia e lo Sviluppo Economico Sostenibile, EniProgetti SpA, Ecole Polytechnique Federale de Lausanne

This paper reports the main design keys and the challenging issues of the Heating and Current Drive System (HCD) of the Divert Tokamak Test (DTT) facility that is under construction at ENEA site in Frascati with the aim to perform studies on the power exhaust in a flexible and easily modifiable environment. The selected HCD systems for DTT are those with the most consolidated technology and expected to be relevant for the future reactor. The status of each system is reported, both in terms of design and procurement, which are well advanced for the system required in the first phase of the DTT exploitation: electron and ion cyclotron resonant heating. The third system is neutral beam injector, based on negative ion acceleration, which will be installed in DTT in a second phase, after the first five years of operation. The full heating power will be reached with the doubling of the radiofrequency power to reach the 45 MW at plasma needed to test the divertor with a power density at reactor level.

National Research CouncilSwiss Federal Institute of Technology LausanneItalian National Agency for New Technologies, Energy, and Sustainable Economic DevelopmentConsorzio RFX

4 days ago

Aug 14

The physics of ballooning-limited ELM-free regimes in EUROfusion tokamaks

Aug 14, 2026

Nuclear Fusion

Mike G Dunne, Michael Faitsch, Olivier Sauter, Eleonora Viezzer, Benoit Labit, Athina Kappatou, David Keeling, Branka Vanovac, Itziar Balboa, Petra Bilkova, et al.

Culham Centre for Fusion Energy, Max-Planck-Institut für Plasmaphysik, Ecole Polytechnique Federale de Lausanne, Academy of Sciences of the Czech Republic, University of Seville

The development of operational scenarios without large Type-I ELMs is of utmost importance for the stable operation and longevity of future tokamaks. The EUROfusion tokamak exploitation program has therefore made the understanding of ELM-free regimes a major topic of exploration across all its contributing devices (ASDEX Upgrade, JET, MAST-Upgrade, TCV, and WEST). An integrated program to investigate a range of Type-I ELM-free regimes has been developed covering the enhanced D-alpha (EDA), magnetic perturbations (MP), negative triangularity (NT), quasi-continuous exhaust (QCE), quiescent H-mode (QH), the baseline small ELMs (SE), I-mode, and X-point radiator (XPR) regimes. This contribution focuses on the development and understanding of the NT and QCE regimes on ASDEX Upgrade, JET, and TCV. The importance of transport via ballooning modes in both regimes is highlighted, as well as the progress in developing access models based on ideal-MHD. In the case of the QCE, this can also be expressed as a minimum separatrix density, which corresponds well to experimentally measured separatrix densities. Particular focus is paid to the performance of the QCE in terms of the achieved pedestal top values, which, when appropriately normalised, do not differ significantly from ELMy H-mode plasmas. This, combined with the predicted minimum separatrix density for the 15~MA ITER baseline plasma, highlight the relevance of the QCE as a potential operational scenario for both ITER and future reactors.

Culham Centre for Fusion EnergyMax Planck Institute for Plasma PhysicsSwiss Federal Institute of Technology LausanneCzech Academy of Sciences

Aug 14, 2026

Aug 10

Challenges of Locked Mode Avoidance in the Low-ν* ITER Baseline Scenario Plasmas in ASDEX Upgrade

Aug 10, 2026

Plasma Physics and Controlled Fusion

Lidia Piron, Thomas Pütterich, Tomas Markovic, Olivier Sauter, Wolfgang Suttrop, Paolo Bettini, M Bonotto, Athina Kappatou, Marc Maraschek, Leonardo Pigatto, et al.

Max-Planck-Institut für Plasmaphysik, Universita degli Studi di Padova, Czech Academy of Sciences Institute of Plasma Physics, Ecole Polytechnique Federale de Lausanne, Universita di Udine

In AUG, the requirement to explore the low-ν* regime within the same ITER baseline scenario parameters, i.e. a Greenwald fraction of ~0.85, q₉₅ ≈ 3, βN ≈ 1.8, and H98 ≈ 1, has been addressed by inducing density pump-out through n=2 magnetic field perturbations. This approach required additionally relaxing the high-δ plasma shape to δ ≈ 0.1 to enable sufficiently strong density pump-out. However, at low density also the generation of locked modes was observed which deteriorates the plasma performance. Several strategies were therefore tested, including model-based error field correction combined with different heating schemes, as well as a core–edge decoupling metric derived from the GPEC code. Nevertheless, these attempts were unsuccessful, largely because the gap between the onset of density pump-out and the excitation of the core mode is very small.

Max Planck Institute for Plasma PhysicsSwiss Federal Institute of Technology Lausanne

Aug 10, 2026

Aug 9

Fast-ion enhanced modeling of neoclassical tearing modes at NSTX and DIII-D

Aug 9, 2026

Plasma Physics and Controlled Fusion

James Yang, Eric Fredrickson, John W Berkery, Robert John La Haye, Mario Podesta

Princeton University Plasma Physics Laboratory, General Atomics, Ecole Polytechnique Federale de Lausanne

A new framework for the solution of modified Rutherford equation including fast ions is successfully applied to interpret the tearing mode stability of two discharges NSTX #134020 and DIII-D #135861. The simulated island width growth rates are in better agreement with the measured island growth rate when the fast ions are included. While constants are multiplied to the polarization current contribution terms for NSTX #134020, no constants are necessary to match the simulated and measured island width growth rates for DIII-D #135861. The estimated island frequencies appear to provide an explanation of the different constants used in the two discharges. The gradient scale lengths suggest that the fast ion contribution can become significant in plasmas with flat thermal ion density profile and steep fast ion density profile.

Princeton Plasma Physics LaboratoryGeneral AtomicsSwiss Federal Institute of Technology Lausanne

Aug 9, 2026

Aug 7

Non-dimensional confinement scaling in similar negative triangularity plasmas on the DIII-D and TCV tokamaks

Aug 7, 2026

Nuclear Fusion

Alessandro Marinoni, Colin Chrystal, Stefano Coda, Reinart Coosemans, Claudio Marini, Mario Podesta, Olivier Sauter, Matteo Agostini, Max E Austin, Emily A Belli, et al.

General Atomics, Ecole Polytechnique Federale de Lausanne, Columbia University, University of California San Diego, Consorzio RFX

Similarity experiments were performed on the DIII-D and TCV tokamaks to explore the scaling of energy confinement in negative triangularity plasmas using non-dimensional variables. Near up-down symmetric plasmas with large top-bottom averaged negative triangularity were created in a lower single null configuration, with the shape of the separatrix being closely matched between the two devices. The normalized energy confinement is found to weakly improve at increasing collisionality and, between the two devices, shows a machine size scaling behavior between Bohm and gyro-Bohm. Engineering scaling on a large DIII-D dataset is in agreement with the non-dimensional experiment.

Consorzio RFXGeneral AtomicsSwiss Federal Institute of Technology LausanneUniversity of California San Diego

Aug 7, 2026

Aug 1

FENNECS 3D: A three-dimensional particle-in-cell code for non-neutral plasma dynamics and diocotron instability simulations

Aug 1, 2026

Physics of Plasmas

P. Giroud-Garampon, J. Loizu, F. Romano, G. Le Bars, J.-P. Hogge

École Polytechnique Fédérale de Lausanne (EPFL)

This work presents the three-dimensional (3D) extension of the FENNECS code, a particle-in-cell framework developed to simulate the dynamics of non-neutral plasmas in complex geometries. The development is motivated by the study of spontaneous electron cloud formation in gyrotron electron guns, which can induce parasitic currents and lead to operational disruptions. The inclusion of 3D effects allows the modeling of the diocotron instability, which plays a major role in limiting the cloud density and driving electron losses. These features are inherently absent from the previous 2D version, where the axisymmetric assumption suppresses all azimuthal dynamics. The 3D capabilities are verified in simplified configurations. Simulations of the diocotron instability in an axially uniform annular electron cloud are found to be in excellent agreement with analytical linear theory. Finite-length effects are also investigated by simulating a cloud confined in a Penning–Malmberg trap, with the code reproducing the expected trends predicted by a linear model. FENNECS 3D is then used to simulate the TRapped Electrons eXperiment, a dedicated setup designed to reproduce the trapping conditions of gyrotron electron guns. Simulations performed under experimentally realistic conditions demonstrate the periodic, self-consistent growth and disruption of the electron cloud due to the diocotron instability. The simulated currents agree quantitatively with experimental measurements in both frequency and amplitude. This work establishes a robust and versatile framework for investigating electron trapping phenomena in gyrotrons and other devices where similar mechanisms are present and represents a significant step forward in the numerical modeling of non-neutral plasmas.

Swiss Federal Institute of Technology Lausanne

Aug 1, 2026

Jul 29

Beam optics analysis by visible cameras applied to the multi-beamlet configuration in the ITER NBI prototype source

Jul 29, 2026

Plasma Physics and Controlled Fusion

Giulia Emma, Margherita Ugoletti, Matteo Agostini, Riccardo Agnello, Riccardo Casagrande, Isabella Mario, Roberto Pasqualotto, Antonio Pimazzoni, Carlo Poggi, Basile Pouradier-Duteil, et al.

Consorzio RFX, ISTP-CNR, Institute for Plasma Science and Technology, University of Padova, École Polytechnique Fédérale de Lausanne (EPFL), ITER Organization

The production of high energy neutral hydrogen/deuterium beams (0.87 MeV/1 MeV) with more than 90% uniformity and extremely low divergence (< 7 mrad) is highly challenging for the realization of the ITER Neutral Beam Injection system. The ITER prototype negative ion source, SPIDER, is in operation at the Neutral Beam Test Facility in Padua and it is equipped with a full set of diagnostics to study and investigate the beam properties. Among them, a system of 15 2D visible cameras, surrounding the vacuum vessel, is employed to measure the beam uniformity and divergence by detecting the light emitted from the beam-background gas interaction. In this paper, the beam divergence measured by these cameras is evaluated for the first time in the multi-beamlet configuration explored during the most recent SPIDER operation. The analysis is performed using the top-view and the side-view cameras, studying both the horizontal and vertical beam profiles through a 1D Gaussian fitting procedure, to estimate the width of the beamlet column or row aligned with the camera's lines of sight. The divergence is then retrieved from the linear fit of the width measured at different positions along the beam propagation direction. The method is here presented and applied to the experimental data acquired with an open beam segment. The dependence of the divergence on the main source and accelerator parameters, namely the RF power, the source filling pressure, and the voltage of the accelerator grids, is investigated. The results are then compared with measurements of the divergence given by the other beam diagnostics available in SPIDER, showing good agreement and validating the use of the visible camera system for the beam optics characterisation in the multi-beamlet operation.

Consorzio RFXITER OrganizationSwiss Federal Institute of Technology Lausanne

Jul 29, 2026

Machine learning aided neutron yield for dud detection based on JET and TFTR Deuterium-Tritium plasmas

Jul 29, 2026

Nuclear Fusion

Lidia Piron, Alessandro Pau, Nicolò Ferron, Eric Fredrickson, Olivier Sauter, Matteo Baruzzo, Clive D Challis, Remi Dumont, Dirk Van Eester, Michael Fitzgerald, et al.

Culham Science Centre, Consorzio RFX, Ecole Polytechnique Federale de Lausanna, Laboratory for Plasma Physics, Max-Plank-Institut für Plasma Physik

as it indicates fusion performance. To optimize Tritium consumption and limit neutron activation, a support function included in the plasma control system called a dud detector will trigger an alarm if the plasma fails to achieve expected fusion performance. This function has been developed and routinely employed at JET during DT campaigns. This study presents machine-learning methods based on a surrogate model of the neutron rate, which can be used as an advanced dud detector. In preparation for DT operations in BEST, HL-3, ITER, and SPARC, we investigate the portability and inherent limitations of these ML methods by analysing similar DT experiments conducted at TFTR.

Max Planck Institute for Plasma PhysicsConsorzio RFXSwiss Federal Institute of Technology Lausanne

Jul 29, 2026

Jul 27

Space structure of the EGAM modes in TCV, experimental observations and modeling

Jul 27, 2026

Plasma Physics and Controlled Fusion

Mykola Dreval, Alessandro Biancalani, Thomas Hayward-Schneider, Alexey Mishchenko, Alexander N Karpushov, Anton Jansen van Vuuren, Umar Ahmed Sheikh, Didier Gossard, Sergei E Sharapov, Baruch Rofman, et al.

Ecole Polytechnique Fédérale de Lausanne (EPFL), Léonard de Vinci Pôle Universitaire, Max-Planck-Institut für Plasmaphysik, Kharkov Institute of Physics and Technology, UKAEA

The complex spatial structure of EGAMs has been recently observed experimentally in the TCV tokamak [M.B. Dreval et al., 2025 Nucl. Fusion 65 016037]. In the present work, we model the spatial structure of EGAM modes in the TCV equilibrium using a realistic fast ion distribution function, implemented in the gyrokinetic particle-in-cell code ORB5. For a peaked radial profile of fast ions, the EGAM spatial structure coincides with that of the conventional GAM, characterized by an n/m=0/0 plasma potential perturbation and an m=1 standing density perturbation, where the amplitude of the density oscillations is proportional to the sine of the poloidal angle. In contrast, for a hollow fast-ion radial profile and a marginally stable mode, our simulations reproduce a complex EGAM spatial structure similar to that observed experimentally in TCV, with two coexisting density fluctuation frequencies at different radial locations.

Max Planck Institute for Plasma PhysicsKharkiv Institute of Physics and TechnologyUnited Kingdom Atomic Energy AuthoritySwiss Federal Institute of Technology Lausanne

Jul 27, 2026

Jul 26

Tungsten erosion and scrape-off layer transport modelling in L-mode helium plasma discharges in ASDEX Upgrade

Jul 26, 2026

Plasma Physics and Controlled Fusion

Gabriele Alberti, Elena Tonello, Carlo Tuccari, Fabio Mombelli, Sebastijan Brezinsek, Timo Dittmar, Antti Hakola, Andreas Kirschner, Karl Krieger, Marcin Rasinski, et al.

Politecnico di Milano, Forschungszentrum Jülich GmbH, Istituto per la Scienza e Tecnologia dei Plasmi, CNR, École Polytechnique Federale de Lausanne (EPFL), VTT Technical Research Centre of Finland Ltd

Due to its unavoidable presence in thermonuclear DT plasmas and to its peculiar effects on materials, investigating the role of helium (He) in plasma-wall interaction (PWI) in current tokamaks is fundamental. In this work, PWI in L-mode He plasma discharges in ASDEX Upgrade (AUG) is modelled by exploiting simplified analytical approaches and two state-of-the-art codes. SOLPS-ITER is employed both to provide a suitable background plasma for erosion simulations and to interpret diagnostics measurements in terms of He+/2+ fraction. In particular, a 50-50% concentration of the two He ions is found in the proximity of the strike-points, while He2+ represents the dominant population farther in the scrape-off layer (SOL). The role of He ion fraction on AUG tungsten divertor erosion is first estimated by means of a simple analytical model and, afterwards, by exploiting ERO2.0, showing the major impact of He2+ in common AUG plasma temperatures. The potential influence of extrinsic impurities on divertor erosion is inferred from the preliminary comparison of ERO2.0 simulation results with experimental erosion measurements in the strike-point region. A comparison between the multi-fluid and kinetic approaches for simulating W erosion and migration reveals significant discrepancies in the predicted tungsten source and transport. In particular, he routinely adopted perfect entrainment assumption in SOLPS-ITER, i.e. setting the same velocity at the magnetic pre-sheath entrance for both main ions and impurities, is found to substantially overestimate the W source compared to ERO2.0 results. Moreover, ERO2.0 predicts a stronger tungsten transport towards the X-point than current SOLPS-ITER simulations without drifts. Comparable W influx into the core can, however, be reproduced in ERO2.0 by reducing the anomalous diffusivity.

Forschungszentrum JülichNational Research CouncilVTT Technical Research Centre of FinlandSwiss Federal Institute of Technology Lausanne

Jul 26, 2026

Jul 17

Kinetic equilibrium prediction at TCV using RAPTOR and FBT

Jul 17, 2026

Nuclear Fusion

C.E. Contré, A. Merle, O. Sauter, S. Van Mulders, R. Coosemans, G. Durr-Legoupil-Nicoud, F. Felici, O. Février, C. Heiss, B. Labit, et al.

Ecole Polytechnique Fédérale de Lausanne (EPFL), ITER Organization, Eindhoven University of Technology

We present results from a new Kinetic-Equilibrium Prediction workflow and shot preparation for full Tokamak à Configuration Variable (TCV) discharges, by coupling predict-first RAPTOR transport simulations with FBT inverse equilibrium calculations. RAPTOR is a 1.5D transport code which has been extensively used for plasma shot optimization and real-time modeling. We show that rapid pre-shot simulations can be performed directly using information from the pulse schedule across a wide range of plasma shapes and scenarios, given an estimate of the confinement quality factor H 98 ( y , 2 ) and line-averaged density. The resulting p ′ and T T ′ profiles are then provided to the pre-shot equilibrium computation performed by FBT—a static free-boundary solver routinely used at TCV—achieving convergence between the two codes in a few iterations. Finally, we show that this coupling, when integrated into the TCV shot preparation, improves the evaluation of the coil currents needed to match the target plasma shape; in particular providing an accurate estimate of critical quantities such as the internal inductance l i and normalized pressure β N , giving more realistic information to tokamak operators about the expected pulse behavior and enabling them to adjust the plan correspondingly.

Swiss Federal Institute of Technology LausanneITER Organization

Jul 17, 2026

Jul 16

Non-inductive high-performance discharges on TCV on the path to steady state

Jul 16, 2026

Nuclear Fusion

S. Coda, C. Piron, I. Voitsekhovitch, M. Agostini, F. Auriemma, L. Cordaro, A. Mele, M. Podestà, S. Garavaglia, A. Jardin, et al.

Consorzio RFX, Ecole Polytechnique Fédérale de Lausanne, Istituto per la Scienza e la Tecnologia dei Plasmi, CNR, ENEA, UKAEA

An extended experimental effort is underway on the TCV tokamak to develop scenarios compatible with long-pulse operation, featuring mostly non-inductively driven current—preferably with a large fraction of bootstrap current. A closely related goal is to achieve good plasma performance, typically measured through the normalized beta β N . This work is part of a broader endeavor involving several European tokamaks, under the auspices of the Tokamak Exploitation Work Package (WPTE) of EUROfusion, and aimed in part at preparing advanced scenarios for the new JT-60SA tokamak, which is the largest such device ever operated and has these scenarios at the core of its mission. This paper reports on the encouraging progress achieved in the last campaign, featuring an extensive set of discharges sustained over multiple current relaxation times ( T pulse ≫ τ R ) with zero flux contribution from the central solenoid (CS), and approaching stationary conditions with β N ∼ 2 and ion temperature ( T i ) rising towards the same order of magnitude as the electron temperature ( T e ). Auxiliary power currently appears to be a key limitation. With increased heating being added in 2027, there is now a realistic prospect of TCV reaching a fully stationary, high- β N , fully non-inductive neutral-beam injection-heated scenario. In the process of exploring the boundaries of this scenario, the hot-electron ( T e ≫ T i ) internal-transport-barrier (ITB) regime was also revisited and temperatures of 12 keV were recorded (a record for TCV non-inductive discharges). Additionally, a fully CS-free current ramp-up, starting only 30 ms after breakdown and displaying robustly negative central magnetic shear, has also been demonstrated, with a smooth continuation into the flat-top, non-inductive, advanced-scenario phase. This scenario, which is accompanied by an electron ITB of varying strength, is also a promising step towards a possible spherical-tokamak power plant. Finally, central-solenoid-free operation in the X -point target divertor configuration has been achieved, with a view to attempting detachment in a closed divertor geometry.

Consorzio RFXSwiss Federal Institute of Technology LausanneItalian National Agency for New Technologies, Energy, and Sustainable Economic DevelopmentUnited Kingdom Atomic Energy Authority

Jul 16, 2026

Jul 15

Validation of the GBS code against COMPASS experimental data

Jul 15, 2026

Nuclear Fusion

P. Macha, J. Seidl, D. Oliveira, D. Galassi, K. Lim, D. Tskhakaya, J. Horacek, J. Adamek, J. Cavalier, P. Bilkova, et al.

Institute of Plasma Physics of the CAS, EPFL, Czech Technical University in Prague, CEA, Nanyang Technological University

This work presents the first full-size turbulence simulation of the COMPASS tokamak edge with the three-dimensional, self-consistent, flux-driven, two-fluid Global Braginskii Solver (GBS) code. The simulation is validated against experimental data from a standard L-mode COMPASS discharge, covering the scrape-off layer (SOL) from the outer midplane to the divertor region. The dataset combines four diagnostic systems and provides 43 observable profiles, including electron temperature and plasma potential measurements that enable the first direct comparison of their fluctuations and higher-order statistics in COMPASS. The validation results show good agreement between simulation and experiment in profile shape, magnitude, and fluctuation levels for most outer midplane observables. The parallel heat-flux fall-off length is also reproduced. In the divertor, the mean profiles agree reasonably well in magnitude, but the simulated fluctuation levels remain significantly underestimated. Advanced blob analysis shows that both simulation and experiment lie mainly in the sheath-connected regime, with partial presence in the connected ideal-interchange regime. The remaining discrepancies in the COMPASS simulation are probably a consequence of simplified parameters and boundary conditions, reflecting limitations that are common to fluid turbulence models. Overall, the validation demonstrates that GBS captures the dominant upstream SOL turbulence dynamics, while identifying divertor physics as the main target for further improvement.

French Alternative Energies and Atomic Energy CommissionSwiss Federal Institute of Technology LausanneInstitute of Plasma Physics of the Czech Academy of Sciences

Jul 15, 2026

Jul 14

3D modelling of thermal loads during unmitigated vertical displacement events in ITER and JET

Jul 14, 2026

Nuclear Fusion

F.J. Artola, A. Redl, S.N. Gerasimov, R.A. Pitts, I.S. Carvalho, M. Kong, G. Simic, A. Loarte, J. Van Blarcum

ITER Organization, Max Planck Institute for Plasmaphysics, UKAEA, Ecole Polytechnique Fédérale de Lausanne (EPFL)

Predicting three-dimensional thermal loads during tokamak disruptions is essential for ITER yet remains weakly developed. We present a physics-based workflow that couples MHD simulations of vertical displacement events with field line tracing on a realistic 3D first wall model and a transient wall thermal response. The approach is validated against JET discharges with beryllium main chamber armour, reproducing key global dynamics, non-axisymmetric current features, and the occurrence (or absence) of melting, thereby building confidence in the methodology. We then apply the same workflow to ITER-relevant conditions with tungsten (W) armour, consistent with the new 2024 ITER re-baseline, to assess disruption heat loads and their 3D localization. The resulting analysis demonstrates the resilience of the ITER W first wall against these events and provides predictions for the energy deposition and current flow profiles. Beyond these studies, the workflow enables scenario-by-scenario estimates of disruption-induced thermal loading, allowing to assess the disruption-budget consumption for these events in future devices.

Max Planck Institute for Plasma PhysicsSwiss Federal Institute of Technology LausanneITER OrganizationUnited Kingdom Atomic Energy Authority

Jul 14, 2026

First observations of ion cyclotron emission in the TCV tokamak

Jul 14, 2026

Nuclear Fusion

A. Jansen van Vuuren, M.B. Dreval, R. Ochoukov, S.E. Sharapov, B.P. Duval, H. Elaian, L. Simons, C. Paraskevopoulos, A.N. Karpushov

Ecole Polytechnique Fédérale de Lausanne (EPFL), Kharkov Institute of Physics and Technology, Max-Planck-Institut für Plasmaphysik, Culham Centre for Fusion Energy (CCFE)

The first observations of ion cyclotron emission (ICE) in the Tokamak à Configuration Variable (TCV) tokamak are reported. The measured ICE frequency closely follows the deuterium ion cyclotron frequency at the magnetic axis, with temporal variations consistent with equilibrium evolution and associated shifts of the magnetic axis. Core ICE is observed primarily during phases with combined electron cyclotron resonance heating (ECRH) and neutral beam injection (NBI). In most discharges the second harmonic dominates, while in others higher harmonics (third or fourth) are observed. Fine spectral structure, including branch splitting and frequency chirping, is frequently detected, together with additional modes consistent with emission at cyclotron harmonics from regions closer to the plasma edge. Core ICE is observed during both co-current and counter-current NBI. The frequency offset of core ICE relative to the ion cyclotron harmonic at the magnetic axis reverses sign between co- and counter-current injection, and this behavior is confirmed in discharges with reversed plasma current. The observed frequency shifts are qualitatively consistent with Doppler-shifted cyclotron resonance arguments.

Kharkiv Institute of Physics and TechnologyMax Planck Institute for Plasma PhysicsSwiss Federal Institute of Technology LausanneCulham Centre for Fusion Energy

Jul 14, 2026

Jul 13

Towards digital twins of fusion systems

Jul 13, 2026

Nuclear Fusion

F. Jenko, J. Ball, D. Borodin, C. Bourdelle, G. Ciraolo, J.E. Cook, J.M. García-Regaña, T. Görler, M. Hoelzl, F. Imbeaux, et al.

Max Planck Institute for Plasma Physics, CEA, Ecole Polytechnique Fédérale de Lausanne (EPFL), Forschungszentrum Jülich GmbH, United Kingdom Atomic Energy Authority

Bridging the gap to next-step devices—while saving valuable time and resources—requires more than semi-empirical models, which struggle to predict plasma behavior in unexplored parameter regimes. Instead, validated simulation tools are essential, leveraging high-fidelity exascale computing and multi-fidelity models, including AI-based surrogates. To address these challenges, the ‘EUROfusion Theory and Advanced Simulation Coordination (E-TASC)’ initiative was launched in 2021. It includes 15 TSVV (Theory, Simulation, Verification, and Validation) projects supported by five Advanced Computing Hubs. This ‘team of teams’ has made substantial progress toward developing digital twins of fusion systems, with key scientific achievements to be presented in the paper. This includes the following topical areas: core performance in burning plasmas, magnetohydrodynamic transients, L–H transitions and ELM-free regimes, plasma exhaust, and plasma–wall interactions—with applications to both tokamaks and stellarators.

French Alternative Energies and Atomic Energy CommissionMax Planck Institute for Plasma PhysicsSwiss Federal Institute of Technology LausanneForschungszentrum JülichUnited Kingdom Atomic Energy Authority

Jul 13, 2026

Axisymmetric global Alfvén eigenmodes in the TCV tokamak

Jul 13, 2026

Nuclear Fusion

M. Dreval, S.E. Sharapov, H.J.C. Oliver, M. Fitzgerald, A.N. Karpushov, A. Jansen van Vuuren, J. Poley, M. Podesta, F. Porcelli

Ecole Polytechnique Fédérale de Lausanne (EPFL), UKAEA, Kharkov Institute of Physics and Technology, Polytechnic University of Turin

Global Alfvén eigenmodes (GAEs) with toroidal mode number n = 0 (i.e. axisymmetric) have been observed in the toroidicity-induced, ellipticity-induced, and above non-circularity-induced frequency ranges in the TCV tokamak. Observation of n = 0 GAEs at multiple frequencies, caused by the periodic structure of the Alfvén continuum in frequency, demonstrates the fundamental nature of these modes. A radial splitting of the n = 0 GAEs has been predicted by linear MHD calculation. This calculation is consistent with the recently observed radial splitting of GAEs in the sub-cyclotron frequency range. Linear MHD codes were used to compute the n = 0 Alfvén continuum and the corresponding eigenmode structures. The modeling confirms that the n = 0 GAEs are located mainly below the minima of the Alfvén continuum, although some modes are observed above the continuum maxima, similar to the sub-cyclotron-frequency GAEs, for which modes above the continuum maxima have also been reported. The n = 0 GAEs have been observed in a variety of discharge types, including low- and high-density plasmas, positive- and negative-triangularity configurations, and discharges with neutral beam injection in both co-current and counter-current directions. A key factor for the appearance of n = 0 GAEs is a positive gradient in the particle energy distribution function, ∂ f /∂ E > 0 (bump-on-tail), which has been confirmed by TRANSP calculations for all discharges.

Kharkiv Institute of Physics and TechnologySwiss Federal Institute of Technology LausannePolytechnic University of TurinUnited Kingdom Atomic Energy Authority

Jul 13, 2026

Jul 1

First study of ICRF minority ion heating scenario on CN-H1 using a 3-Dimensional full wave code

Jul 1, 2026

Plasma Physics and Controlled Fusion

L Yin, C Slaby, Q Ou, J P Graves, P W Zheng, D Xiang, X Y Gong, Z K Gao, Y Chen

Max Planck Institute for Plasma Physics, University of South China, Ecole Polytechnique F´ed´erale de Lausanne (EPFL), University of York

For the first time, a three-dimensional (3D) simulation of the minority ion heating scenario with ion cyclotron waves on the CN-H1 stellarator was performed using the LEMan code, the full wave solver inside the SCENIC ICRH package. The simulation results provide a reasonable explanation for the edge-peaked electron temperature profile observed in ion cyclotron resonance heating (ICRH) experiments on the original H-1 heliac. A new ICRH scheme for effective ion heating in the CN-H1 stellarator is also proposed. In this scheme, the plasma density near the antenna is increased, the wave frequency is adjusted to match the on-axis cyclotron resonance, and the minority ion concentration is selected within an optimal range of 10%–20%, considering the influences of the left-handed electric field and the number of resonant ions. The simulation results imply that the fast wave can tunnel through the evanescent region into the plasma, leading to effective ion absorption at the resonant surface, where the ion absorption fraction exceeds that of electrons. Meanwhile, significant toroidal variations exist in ICRH due to the unique non-axisymmetric configuration of CN-H1. This research focuses on the unique 3D configuration and parameter characteristics of the CN-H1 stellarator, providing a new improved ICRH scheme and parameter reference for upcoming ICRH experiments.

Max Planck Institute for Plasma PhysicsSwiss Federal Institute of Technology Lausanne

Jul 1, 2026

Relaxation oscillations driven by the diocotron instability in trapped electron clouds

Jul 1, 2026

Physics of Plasmas

P. Giroud-Garampon, F. Romano, J. Loizu, J.-P. Hogge, G. Scimone, J. Genoud, F. Braunmüller, M. Podestà, T. Goodman

École Polytechnique Fédérale de Lausanne (EPFL)

We report the first three-dimensional kinetic simulations that self-consistently reproduce relaxation oscillations of high-density, strongly rotating electron clouds confined in Penning-like potential wells. Using the finite element non-neutral electron clouds simulator code, we model the Trapped Electrons eXperiment (T-REX), a dedicated setup designed to study electron cloud dynamics relevant to gyrotron electron guns. The simulations are in quantitative agreement with experiment and show that the observed periodic current bursts originate from the diocotron instability developing within the trapped cloud, driving rapid cross field transport and electron loss. The presence of the diocotron mode is further confirmed by spatiotemporal current measurements from dedicated probes in T-REX.

Swiss Federal Institute of Technology Lausanne

Jul 1, 2026