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Sep 15

Negative triangularity studies in view of DTT operations

Paola Mantica, Lorenzo Aucone, Alessandro Balestri, Alberto Mariani, Roberto Ambrosino, Justin Ball, A. Castaldo, Stefano Coda, Tim Happel, Joerg Hobirk, et al.

Plasma Physics and Controlled FusionSep 15, 2026Plasma & Confinement AI, Modeling & Simulation

This paper summarizes experimental and modelling work carried out across the last 5 years on Negative Triangularity (NT) scenarios in view of future DTT operations. The shapes foreseen for DTT have been tested experimentally on TCV and ASDEX Upgrade (AUG). Integrated modelling using ASTRA/TGLF and local gyrokinetic simulations using GENE have been performed on the experimental results and to predict DTT scenarios. Experiments and modelling find a stronger beneficial effect of NT in TCV than in AUG. DTT predictions are more in line with AUG results. Various mechanisms to explain this difference have been examined and are discussed. In all devices, the NT scenarios provide a viable ELM-free alternative to Positive Triangularity ELMy H-modes, with central values of pressure comparable or even higher.

Max Planck Institute for Plasma PhysicsUniversity of Milano-BicoccaNational Research CouncilSwiss Federal Institute of Technology Lausanne

Sep 4

Helium‑3 minority heating with ion cyclotron range of frequencies (ICRF) in the experimental advanced superconducting tokamak

Yongxin Zhu, Wei Zhang, Yevgen Kazakov, Jinhua Wu, Paola Mantica, Gabriele Cassella, Tao Jin, X. J. Zhang, Lunan Liu, Hua Yang, et al.

Nuclear FusionSep 4, 2026Plasma & Confinement Control & Diagnostics Heating & Current Drive AI, Modeling & Simulation

During the 2025 campaign, helium-3 ( 3 He) minority heating with waves in the ion cyclotron range of frequencies (ICRF) was investigated for the first time on the Experimental Advanced Superconducting Tokamak (EAST). With the lowest available ICRF frequency of f IC = 27 MHz, experiments were conducted at a high toroidal magnetic field of B t = 2.8 T and plasma current I p = 450 kA. To optimize 3 He minority heating, the variation of 3 He concentration was systematically explored. Real-time feedback control of the 3 He concentration was successfully implemented through spectroscopic measurement and closed-loop regulation of the 3 He gas injection, demonstrating the feasibility of the control system functions. The ICRF heating efficiency reached a maximum at a minority concentration of ∼8-9%, with the core electron temperature increasing from approximately 5.0 to 7.0 keV and the ion temperature from approximately 1.3 to 1.9 keV under 2.9 MW of ICRF power. These results are in good agreement with simulations from the two-dimensional full-wave code TORIC. Experiments further indicate that higher plasma density enhances 3He heating efficiency. We also briefly discuss the strategy for future 3 He ICRF experiments on EAST.

National Research CouncilHefei Institutes of Physical ScienceUniversity of Milano-BicoccaEcole Royale Militaire-Koninklijke Militaire School

Aug 24

Beam optics and stripping losses in a full-scale ITER negative ion source: multibeamlet analysis by beam emission spectroscopy

Riccardo Agnello, Marco Barbisan, Roberto Pasqualotto, Antonio Pimazzoni, Emanuele Sartori, Barbara Zaniol, Edgard Zuin

Plasma Physics and Controlled FusionAug 24, 2026Control & Diagnostics Heating & Current Drive

In this work, Beam Emission Spectroscopy (BES) is applied to the investigation of beam divergence and stripping losses in the full-scale ITER negative ion source prototype SPIDER, operating in multibeamlet configuration. A semi-analytical model is developed to simulate the emission spectra produced by overlapping beamlets, accounting for realistic beamlet divergence, aiming, and beam composition along the accelerator and drift regions. The comparison between synthetic and experimental spectra shows that the Doppler broadening measured in multibeamlet operation cannot be interpreted solely in terms of single-beamlet divergence, but results from the combined effects of beamlet overlap, residual magnetic deflections, electrostatic repulsion, and halo contributions. Using beamlet parameters independently obtained from calorimetric diagnostics, the model reproduces a significant fraction of the experimentally measured divergence. Moreover, the possibility of displacing a line-of-sight allows the detection of variations in the populations of particles with different divergences, namely the core and halo components, across the beam. As a phenomenological characterization, stripping losses are systematically quantified over a wide range of operational parameters, showing an approximately linear increase with source pressure and values consistent with previous single-beamlet studies. These results demonstrate the capability of BES, combined with multibeamlet modelling, to support beam optimization and performance assessment in ITER-relevant negative ion sources.

Swiss Federal Institute of Technology LausanneNational Research Council

Plasma properties in negative-ion beam sources for fusion: recent results and challenges in view of ITER

Emanuele Sartori, Valeria Candeloro, Isabella Mario, Antonio Pimazzoni, Carlo Poggi, Gianluigi Serianni, Pierluigi Veltri, Matteo Brombin, Riccardo Casagrande, Michele Fadone, et al.

Plasma Physics and Controlled FusionAug 24, 2026Control & Diagnostics Heating & Current Drive AI, Modeling & Simulation

Large plasma sources are employed in negative ion based heating neutral beam injectors for fusion applications. A review of the ITER beam source plasma properties is presented, in comparison with negative ion sources of comparable size, based on the latest experimental measurements from SPIDER and supporting numerical simulations. Spatial investigation of plasma parameters using several diagnostics, including the beam itself, retarding field energy analysers, optical emission spectroscopy, movable and fixed Langmuir probes, is key to understanding the source physics, to support the operation and improve the source performances. The influence of multiple rf-driver configuration on uniformity and the improvement flexibility it provides, as well as the implications of control parameters like filter field and plasma grid bias are examined. Similarities and differences with other giant negative ion sources are discussed to highlight the key physical processes leading to the optimal operation and viable paths for possible improvements of the ITER source design.

National Institute for Fusion ScienceNational Research Council

Aug 21

Development of a high-current, high fusion performance scenario on JET: physics insights and operational challenges

Luca Garzotti, Domenico Frigione, Peter J Lomas, Fernanda Rimini, Dirk Van Eester, Vito Konrad Zotta, Spyridon Aleiferis, Edoardo Alessi, Fulvio Auriemma, Rennan Bianchetti Morales, et al.

Plasma Physics and Controlled FusionAug 21, 2026Plasma & Confinement Materials & Plasma-Facing Components AI, Modeling & Simulation

Since the installation of a beryllium-tungsten(Be/W) first wall on JET an intense scenario development programme has taken place to realize a high-current (3.5-4 MA) scenario, denominated JET baseline scenario, with $q_{95} \sim 3$, $\beta_N \sim 1.8$ and capable of delivering high fusion performance ($P_{fusion} > 10$ MW) for 5 s in the D-T campaigns conducted in 2021 and 2023. The JET baseline scenario was realized in D-T at 3.5 MA in 2021 (DTE2 campaign), but, despite achieving transitorily $P_{fus} \sim 8$ MW, it could not be sustained for more than 3 s. In this paper we will revisit and expand the analysis of the baseline scenario at 3.5 MA and present new results obtained in D-T at 3.0 MA in DTE3, where we were able to sustain the scenario for 5 s. We will also present recent modelling results showing how available semi-empirical and first-principles transport models can explain a variety of phenomena ranging from fusion performance, impurity transport and control of the fuelling mix. Many of these points are potentially relevant for bigger machines such as ITER. Finally, we will discuss open questions and improvements to our present modelling capabilities required to extrapolate the results to power plant devices.

Institute of Plasma Physics and Laser MicrofusionNational Research CouncilCulham Centre for Fusion EnergyUnited Kingdom Atomic Energy Authority

Aug 17

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

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

Nuclear FusionAug 17, 2026Plasma & Confinement Heating & Current Drive Fusion Plant Engineering

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

Aug 6

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

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

Plasma Physics and Controlled FusionAug 6, 2026Plasma & Confinement Materials & Plasma-Facing Components AI, Modeling & Simulation

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

Aug 5

Alpha particle velocity- and orbit-space sensitivity of gamma-ray spectroscopy diagnostics based on the 10 B(α,pγ) 13 C reaction

Massimo Nocente, Alessandro Ciurlino, Andrea Valentini, Henrik Järleblad, Yevgen Kazakov, Vasily Kiptily, Mads Rud Larsen, Bruno Coriton, Gabriele Croci, Andrea Dal Molin, et al.

Nuclear FusionAug 5, 2026Plasma & Confinement Control & Diagnostics AI, Modeling & Simulation

A key challenge on the path towards burning plasmas is the measurement of the alpha particle phase space. Among the few experimental options available, gamma-ray spectroscopy is a key method. Previous demonstrations at JET were based on reactions between alpha particles and beryllium as the target impurity, but this is no longer applicable, neither at ITER with a tungsten-based first wall, nor in other forthcoming burning plasma experiments. On the other hand, owing to the use of boron injection for plasma operations in tungsten devices, gamma-ray reactions between the alpha particles and boron impurities have been proposed as an alternative. This work presents the first numerical evaluation of the velocity-space and orbit-space sensitivity of boron-based gamma-ray spectroscopy to the alpha particle phase space, focusing on the 10 B(α,pγ) 13 C reaction. Depending on the emission peak, we find that measurements can be separately sensitive to selected super- and sub-alfvenic velocities, with an enhanced sensitivity towards particles on trapped and potato orbits, for the case of radial lines of sight. Information on co- and counter-going alphas may be accessed only by more refined spectral shape analysis or if a tangential line of sight is deployed. The results are relevant to establish a bridge between the indirect gamma-ray spectroscopy measurements and the alpha particle phase space. They furthermore provide a quantitative input to determine which wave-alpha particle resonant interactions may (or may not) be measurable with boron based gamma-ray spectroscopy, depending on the observation geometry.

University of Milano-BicoccaNational Research CouncilTechnical University of DenmarkITER Organization

Aug 2

Two-fluid boundary turbulence simulations in reversed field pinch plasmas

M. Giacomin, B. Momo, I. Predebon, N. Vianello, M. Zuin

arXiv (physics.plasm-ph)Aug 2, 2026Plasma & Confinement AI, Modeling & Simulation

Turbulent transport in magnetic confinement fusion devices governs the overall plasma confinement properties and regulates the plasma-material interaction at the first wall. In the plasma boundary, turbulence is typically investigated through three-dimensional two-fluid flux-driven turbulence simulations. In this work, the GBS boundary turbulence code is extended to enable turbulence simulations in reversed field pinch configurations, encompassing the reversal surface and an arbitrary level of magnetic chaos. The differential operators implemented in the code are modified to avoid the approximations of large-aspect ratio and weak poloidal magnetic field. Three-dimensional Poisson and Ampere solvers are implemented to allow for turbulence simulations in conditions of partially or fully disrupted magnetic flux surfaces. This modified version of the GBS code is then applied to simulate turbulence in the boundary of RFX-mod reversed field pinch plasmas. Turbulent eddies across the reversal surface show properties similar to those typically found in tokamak boundary turbulence simulations. Despite the good agreement found with experimental measurements, these simulations reveal a significant limitation of the fluid-based turbulence modeling of the edge region in reversed field pinch plasmas, which arises from the intrinsically short parallel connection length. This conclusion is also supported by a linear gyrokinetic analysis that identifies trapped electron modes as the dominant microinstability in this region.

National Research CouncilConsorzio RFX

Jul 31

A Neural Operator Closure for Landau Damping in Electrostatic Plasma

Samuel Burles, Enrico Camporeale, Oreste Pezzi

arXiv (physics.plasm-ph)Jul 31, 2026AI, Modeling & Simulation

We present a data-driven plasma fluid closure for both linear and nonlinear electrostatic Landau damping in one dimension. A Fourier Neural Operator (FNO) is trained online within a differentiable fluid solver, with the loss computed on trajectories produced by the closed fluid simulation rather than on individual kinetic snapshots. The closure is non-Markovian, acting on a trailing window of the resolved moment history so as to represent the memory of the unresolved dynamics. We demonstrate that a single FNO trained in this way reproduces both linear and nonlinear Landau damping, generalises to initial perturbation amplitudes outside the training set, and remains numerically stable when deployed in independent fluid simulations. In the nonlinear regime the learned heat flux reproduces the resolved-moment dynamics without matching the kinetic heat flux pointwise, behaving as an effective closure that compensates for the truncated higher moments, though the learned specific flux is expected to depend on the numerical scheme and training data. A sensitivity analysis of the trained model shows that it computes a genuine moment-to-flux relation whose reliance on the memory window is physically structured.

National Research CouncilUniversity of Colorado at Boulder

Jul 29

Comparative analysis between particle tracing model and thermographic data for a MeV class beam for fusion application

Antonio Pimazzoni, Piero Agostinetti, Giuseppe Chitarin, Giulia Emma, Mieko Kashiwagi, Kisaki Masashi, Nicolo Marconato, Isabella Mario, Basile Pouradier-Duteil, Beatrice Segalini, et al.

Plasma Physics and Controlled FusionJul 29, 2026Heating & Current Drive AI, Modeling & Simulation

For the ITER experimental fusion reactor up to 3 heating neutral beams (HNBs) are foreseen. Each HNB will generate 1280 individual beamlets of H-/D- ions which will be accelerated up to 870 keV/1 MeV, neutralized and focused into the tokamak plasma, to provide up to 16.5 MW of heating power. To this purpose, divergence and aiming of each beamlet are required to be ≤7 mrad and within ± 2 mrad, respectively. An accurate compensation is thus essential, both for the magnetic deflection induced by the magnets embedded in the extraction grid (necessary to immediately deflect the co-accelerated electrons) and for the Coulomb repulsion among the beamlets. The Asymmetric Deflection Compensation Magnets (ADCM), the solution developed for the full-scale ITER HNB prototype called MITICA, was recently tested, for the first time on a MeV class beam, at the MegaVolt Test Facility (MTF) at QST (Naka, Japan). In these experiments, a MITICA-like extraction grid was built and installed on MTF. In this work, the beam pattern measured on a calorimeter made of unidirectional carbon fiber composite (1D-CFC) is compared with the predictions from simulations by the numerical code IBSimu, in order to develop methodologies and identify limitations for its application for MITICA exploitation and improvements. The model accuracy varied with experimental conditions; in all the cases however the proposed methodology proved very valuable in providing trends and dependencies.

French Alternative Energies and Atomic Energy CommissionConsorzio RFXNational Research Council

Jul 21

The Divertor Tokamak Test Facility Research Plan

Gerardo Giruzzi, P Martin, Clemente Angioni, Sebastijan Brezinsek, Flavio Crisanti, Giacomo Dose, Matteo Valerio Falessi, Paolo Innocente, Paola Mantica, Eric Nardon, et al.

Nuclear FusionJul 21, 2026Plasma & Confinement Materials & Plasma-Facing Components Fusion Plant Engineering AI, Modeling & Simulation

The Divertor Tokamak Test facility (DTT) is a device presently under construction at the ENEA site in Frascati (Italy) in the framework of a joint public/private partnership. It has been designed as a superconducting tokamak with breakeven class performance, with the main objective of developing credible solutions for heat and particle exhaust, a key challenge in view of future fusion reactors. This needs to be addressed in a core-edge integrated approach, to assess the compatibility of exhaust solutions with reactor relevant core performance. In this paper, an overview is provided of the DTT research plan, recently developed by an international team. It covers the DTT programmatic objectives, research strategy and expected scientific contributions connected with the device characteristics, not only in the key area of heat exhaust and edge plasma physics, but also on other subjects of high fusion relevance, such as MHD stability in high performance scenarios, transport and turbulence, energetic particle physics, validation of advanced theoretical developments, as well as tests of technological solutions for reactor relevant components.

Max Planck Institute for Plasma PhysicsConsorzio RFXItalian National Agency for New Technologies, Energy, and Sustainable Economic DevelopmentNational Research CouncilFrench Alternative Energies and Atomic Energy Commission

Jul 1

Dimensional isotope scaling of heat and particle transport between JET deuterium and tritium L-mode plasmas

T. Tala, A. Mariani, A.E. Järvinen, A. Salmi, F. Albert, I.S. Carvalho, A. Chomiczewska, E. Delabie, J. Ferreira, W. Gromelski, et al.

Nuclear FusionJul 1, 2026Plasma & Confinement AI, Modeling & Simulation

The dimensionally matched deuterium–tritium pulse pair under JET L-mode conditions showed 13%–16% improvement in the energy confinement time in favour of the tritium pulse. This favourable isotope scaling can be seen clearly in the effective diffusion coefficients throughout the radius. The isotope scaling originates dominantly from the electron heat transport channel and from the edge part of the plasma. The phase and amplitude profiles in response to the gas puff modulation robustly show that there is no room for a large isotope scaling in the particle transport channel in the core plasma at ρ tor ⩽ 0.95 . This can also be seen in the derived particle transport coefficients between the deuterium and tritium pulses. EDGE2D-EIRENE simulations found that the radial ionisation profiles are very similar between the dimensionally matched deuterium and tritium identity pulses. A similar deviation from the gyro-Bohm scaling, i.e. strong isotope scaling favouring tritium in heat transport was found with gyrokinetic simulations in the edge at ρ tor = 0.95 under the JET L-mode conditions. The strong edge isotope scaling favouring tritium is consistent with the experimental observation. This edge isotope effect ρ tor = 0.95 in the GENE simulations is also much larger than found in the core plasma ρ tor = 0.6 when comparing similarly deuterium and tritium simulation results. Both the experimental results and the GENE simulations suggest that the isotope mass scaling is a nonlinear function of the isotope mass itself, being significantly stronger between deuterium and tritium than between hydrogen and deuterium, at least in JET L-mode conditions.

United Kingdom Atomic Energy AuthorityNational Research CouncilInstitute of Plasma Physics and Laser Microfusion