Plasma Physics and Controlled Fusion - IOPscience

Plasma Physics and Controlled Fusion - IOPscience
Plasma Physics and Controlled Fusion
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Plasma Physics and Controlled Fusion
is a monthly publication dedicated to the dissemination of original results on all aspects of plasma physics and associated science and technology.
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The following article is
Open access
The new ITER baseline, research plan and open R&D issues
A Loarte
et al
2025
Plasma Phys. Control. Fusion
67
065023
View article
, The new ITER baseline, research plan and open R&D issues
PDF
, The new ITER baseline, research plan and open R&D issues
A new baseline (NB) has been proposed by the ITER Project to ensure a robust achievement of the Projects’ goals, in view of past challenges including delays incurred due to the Covid-19 pandemic, technical challenges in completing first-of-a-kind components and in nuclear licensing. The NB includes modifications to the configuration of the ITER device and its ancillaries (e.g. change from beryllium to tungsten as first wall material, modification of the heating and current drive mix, etc.) as well as additional testing of components (e.g. toroidal field coils) or phased installation (start with inertially cooled first wall before later installation of the final actively water-cooled components) to minimise operational risks. In the NB, the ITER research plan (IRP) will be divided into three main phases: (a) start of research operation, with 40 MW of ECH and 10 MW of ICH, which will focus on the demonstration of 15 MA operation in L-mode, commissioning of all required systems, including disruption mitigation, and the demonstration of H-mode plasma operation in deuterium; (b) DT-1, with 60–67 MW of ECH, 33 MW of neutral beam injection (NBI) and 10–20 MW of ICH, which will demonstrate robust operation in high confinement H-mode plasmas in DT up to
⩾ 10 and for burn durations of 300–500 s within an accumulated neutron fluence of ∼1% of the ITER machine’s lifetime total, and; (c) DT-2, with up to 67 MW of ECH, up to 49.5 MW of NBI and up to 20 MW of ICH, with the ITER tokamak and ancillaries in their final configuration to demonstrate routine operation in DT plasmas at high
and the
⩾ 5 long-pulse and steady-state scenarios to the final neutron fluence and to perform R&D on nuclear fusion reactor issues. The logic, physics basis, modelling and experimental evaluations carried out to support the NB and the associated IRP are described. These include the impact of the tungsten wall on plasma scenarios and associated risk mitigation measures, as well as the optimisation of the tokamak components and ancillaries to minimise Project risks. Open R&D issues related to these evaluations and mitigation measures are also described together with experimental, modelling and validation activities required to address them.
The following article is
Open access
MANTA: a negative-triangularity NASEM-compliant fusion pilot plant
The MANTA Collaboration
et al
2024
Plasma Phys. Control. Fusion
66
105006
View article
, MANTA: a negative-triangularity NASEM-compliant fusion pilot plant
PDF
, MANTA: a negative-triangularity NASEM-compliant fusion pilot plant
The MANTA (Modular Adjustable Negative Triangularity ARC-class) design study investigated how negative-triangularity (NT) may be leveraged in a compact, fusion pilot plant (FPP) to take a ‘power-handling first’ approach. The result is a pulsed, radiative, ELM-free tokamak that satisfies and exceeds the FPP requirements described in the 2021 National Academies of Sciences, Engineering, and Medicine (NASEM) report ‘Bringing Fusion to the U.S. Grid’ (2021
Bringing Fusion to the U.S. Grid
). A self-consistent integrated modeling workflow predicts a fusion power of 450 MW and a plasma gain of 11.5 with only 23.5 MW of power to the scrape-off layer (SOL). This low
SOL
together with impurity seeding and high density at the separatrix results in a peak heat flux of just 2.8 MW m
−2
. MANTA’s high aspect ratio provides space for a large central solenoid (CS), resulting in ∼15 minute inductive pulses. In spite of the high B fields on the CS and the other REBCO-based magnets, the electromagnetic stresses remain below structural and critical current density limits. Iterative optimization of neutron shielding and tritium breeding blanket yield tritium self-sufficiency with a breeding ratio of 1.15, a blanket power multiplication factor of 1.11, toroidal field coil lifetimes of
MW · yr, and poloidal field coil lifetimes of at least
MW · yr. Following balance of plant modeling, MANTA is projected to generate 90 MW of net electricity at an electricity gain factor of
. Systems-level economic analysis estimates an overnight cost of US$3.4 billion, meeting the NASEM FPP requirement that this first-of-a-kind be less than US$5 billion. The toroidal field coil cost and replacement time are the most critical upfront and lifetime cost drivers, respectively.
The following article is
Open access
XFEL imaging techniques for high energy density and inertial fusion energy research at HED-HiBEF
Alejandro Laso Garcia
et al
2026
Plasma Phys. Control. Fusion
68
035027
View article
, XFEL imaging techniques for high energy density and inertial fusion energy research at HED-HiBEF
PDF
, XFEL imaging techniques for high energy density and inertial fusion energy research at HED-HiBEF
The imaging platform developed at the High Energy Density-Helmholtz International Beamline for Extreme Fields (HED-HiBEF) instrument at the European X-ray Free Electron Laser (XFEL) and its applications to HED and fusion related research are presented. The platform combines the XFEL beam with the high-intensity short-pulse laser ReLaX and the high-energy nanosecond-pulse laser DiPOLE-100X. The spatial resolution is better than 500 nm and the temporal resolution of the order of 50 fs. The influence of the XFEL source in the x-ray imaging method is discussed. Free-propagation x-ray phase contrast imaging and Talbot-Lau imaging setups are shown. We show examples of blast waves and converging cylindrical shocks in aluminum, resonant absorption measurements of specific charged states in copper with ReLaX and planar shocks in polystyrene material generated by DiPOLE-100X. For the first time, we show the application of Talbot-Lau interferometry to convergent cylindrical shocks as well as resonant absorption processes. We also discuss the possibilities introduced by combining this imaging platform with a kJ-class laser.
The following article is
Open access
Contemporary particle-in-cell approach to laser-plasma modelling
T D Arber
et al
2015
Plasma Phys. Control. Fusion
57
113001
View article
, Contemporary particle-in-cell approach to laser-plasma modelling
PDF
, Contemporary particle-in-cell approach to laser-plasma modelling
Particle-in-cell (PIC) methods have a long history in the study of laser-plasma interactions. Early electromagnetic codes used the Yee staggered grid for field variables combined with a leapfrog EM-field update and the Boris algorithm for particle pushing. The general properties of such schemes are well documented. Modern PIC codes tend to add to these high-order shape functions for particles, Poisson preserving field updates, collisions, ionisation, a hybrid scheme for solid density and high-field QED effects. In addition to these physics packages, the increase in computing power now allows simulations with real mass ratios, full 3D dynamics and multi-speckle interaction. This paper presents a review of the core algorithms used in current laser-plasma specific PIC codes. Also reported are estimates of self-heating rates, convergence of collisional routines and test of ionisation models which are not readily available elsewhere. Having reviewed the status of PIC algorithms we present a summary of recent applications of such codes in laser-plasma physics, concentrating on SRS, short-pulse laser-solid interactions, fast-electron transport, and QED effects.
The following article is
Open access
Machine learning and Bayesian inference in nuclear fusion research: an overview
A Pavone
et al
2023
Plasma Phys. Control. Fusion
65
053001
View article
, Machine learning and Bayesian inference in nuclear fusion research: an overview
PDF
, Machine learning and Bayesian inference in nuclear fusion research: an overview
This article reviews applications of Bayesian inference and machine learning (ML) in nuclear fusion research. Current and next-generation nuclear fusion experiments require analysis and modelling efforts that integrate different models consistently and exploit information found across heterogeneous data sources in an efficient manner. Model-based Bayesian inference provides a framework well suited for the interpretation of observed data given physics and probabilistic assumptions, also for very complex systems, thanks to its rigorous and straightforward treatment of uncertainties and modelling hypothesis. On the other hand, ML, in particular neural networks and deep learning models, are based on black-box statistical models and allow the handling of large volumes of data and computation very efficiently. For this reason, approaches which make use of ML and Bayesian inference separately and also in conjunction are of particular interest for today’s experiments and are the main topic of this review. This article also presents an approach where physics-based Bayesian inference and black-box ML play along, mitigating each other’s drawbacks: the former is made more efficient, the latter more interpretable.
The following article is
Open access
Integrated modelling of tokamak plasmas: progress and challenges towards ITER operation and reactor design
C Bourdelle 2025
Plasma Phys. Control. Fusion
67
043001
View article
, Integrated modelling of tokamak plasmas: progress and challenges towards ITER operation and reactor design
PDF
, Integrated modelling of tokamak plasmas: progress and challenges towards ITER operation and reactor design
In tokamak plasmas, non-linear interplay between transport and sources/sinks takes place for all transported quantities (current, heat, particles and momentum). Thanks to integrated modelling frameworks, we can iterate physics-based quasilinear turbulent transport models over multiple confinement times. Such modelling allows us to predict current, temperature, density and rotation profiles, and to disentangle the causality at play behind the modelled time evolution. An intense validation effort of such modelling against experimental measurements has been ongoing and has progressed our understanding. In dynamical phases, the so-called ‘cold pulse’ physics have been explained in the AUG tokamak, the isotope impact in plasma current ramp-up is understood in the JET tokamak, and the impact of the particle source (from neutral beam injection) on tungsten core accumulation has been clarified in JET and AUG. In stationary phases, the saturation of the ion temperature in electron-heated WEST plasmas has been clarified, and the energy content has been predicted with higher accuracy than empirical scaling laws with respect to the plasma current, magnetic field, plasma size and gas fueling, both in L and H modes on AUG. The validation of physics-based integrated modelling allows control optimisation in preparation for ITER operation as well as risk reduction for the design of future reactors. However, despite the reported progress, physics gaps remain on this path. For example, unlike today’s devices, ITER-class devices will be opaque to neutrals and fuelled by pellets. In the absence of a physical understanding of the transport in the pedestal, extrapolation is uncertain. Moreover, in burning plasmas, the non-linear coupling between the central core profiles and the fusion power is very strong. The uncertainties in profile predictions due to unverified and unvalidated reduced transport models in such high-pressure plasmas lead to uncertain fusion power predictions. Solutions on how to address these challenges within integrated modelling will be proposed.
The following article is
Open access
Global gyro-kinetic ion temperature gradient and trapped electron mode turbulence modelling in
-point geometry in negative and positive triangularity
M Bécoulet
et al
2026
Plasma Phys. Control. Fusion
68
035031
View article
, Global gyro-kinetic ion temperature gradient and trapped electron mode turbulence modelling in X-point geometry in negative and positive triangularity
PDF
, Global gyro-kinetic ion temperature gradient and trapped electron mode turbulence modelling in X-point geometry in negative and positive triangularity
Comparative modelling of ion temperature gradient (ITG)/trapped electron mode (TEM) turbulence in negative (NT) and positive (PT) triangularity plasma shapes was done using the nonlinear global full-f gyrokinetic particle code JOREK-GK in the realistic
-point tokamak geometry including the Scrape Off Layer (SOL) for TCV and DIII-D parameters. A comparison of JOREK-GK code with the gyrokinetic codes GS2 and GENE was done using NT/PT triangularity TCV L-modes parameters showing good agreement between codes in linear growth rates and clear beneficial effect of NT as compared to PT. Global non-linear modelling of the ITG/TEM saturated turbulence for realistic DIII-D NT pulses was done and compared with numerically constructed PT equilibrium with the same plasma profiles. Existence of longer correlation length of density fluctuations in PT compared to NT was demonstrated. Stronger and more sheared zonal flows are generated via Reynolds stress in NT compared to PT. These factors are stabilizing for TEM/ITG turbulence in NT and lead to smaller heat fluxes and heat conductivities in NT compared to PT configuration. Weak dependence of plasma confinement on collisionality and plasma rotation was found in modelling of DIII-D NT shots similar to the experiment. The confinement scaling with normalized ion gyro-radius
* was estimated both for NT and PT. Bohm-like scaling was obtained in both configurations, however with better confinement for NT compared to PT which could be favourable factor for reactor size machines.
The following article is
Open access
Nanofoam in action: a versatile tool for laser-plasma interaction experiments
Alessandro Maffini
et al
2026
Plasma Phys. Control. Fusion
68
035007
View article
, Nanofoam in action: a versatile tool for laser-plasma interaction experiments
PDF
, Nanofoam in action: a versatile tool for laser-plasma interaction experiments
Low-density near-critical materials in laser-plasma interaction (LPI) stand out for their capability in enhancing the coupling between the laser radiation and the target. Indeed, they can be exploited for fundamental physics studies, optimised particle acceleration for practical applications, and inertial confinement fusion. However, the modelling of complex non-linear phenomena occurring during the interaction of these materials and high-intensity lasers, together with the accurate control and characterisation of their physical properties, are still object of intense research. In this context, near-critical nanofoams produced via pulsed laser deposition represent a promising option owing to the versatility and controllability of their deposition technique. In this paper, we report on our modelling and experimental activities related to laser-nanofoam interaction. In particular, we first present the deposition methodology, focusing on the production of nanofoams with controlled composition and morphology. Then, we show our numerical strategy to model the foam aggregation. We also discuss how the nanofoam morphology affects the LPI by integrating the realistic nanostructure in particle-in-cell simulations, focusing on various regimes of interaction. Lastly, we present examples of applications of nanofoam-based targets via numerical simulations and experiments, focusing also on the open issues for reaching the requirements for full-fledged applications. Our work demonstrates nanofoam-based targets as a versatile tool to effectively optimise and advance LPI physics.
The following article is
Open access
Commissioning of a multi-GeV electron spectrometer at ELI-NP
Diana Catana
et al
2026
Plasma Phys. Control. Fusion
68
045001
View article
, Commissioning of a multi-GeV electron spectrometer at ELI-NP
PDF
, Commissioning of a multi-GeV electron spectrometer at ELI-NP
A high-resolution spectrometer is necessary for characterizing laser-wakefield accelerated multi-GeV electron beams. During tight beam-time schedules and high-repetition rate experimental conditions, robust real-time monitoring tools and suitable data analysis methods have to be developed. Here, we report in detail the spectrometer system, simulated in Geant4, and the dipole magnetic field, measured and modeled in COMSOL, for an accurate characterization of the energy spectrum of the electron beam. We present a set of computational tools employed in real-time diagnostics, image processing, and energy spectra reconstruction.
The following article is
Open access
A review of collaborative studies between the NSTX/-U and MAST/-U spherical tokamaks
J W Berkery
et al
2025
Plasma Phys. Control. Fusion
67
053001
View article
, A review of collaborative studies between the NSTX/-U and MAST/-U spherical tokamaks
PDF
, A review of collaborative studies between the NSTX/-U and MAST/-U spherical tokamaks
The National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratory in the United States, and the mega ampere spherical tokamak (MAST) at the United Kingdom Atomic Energy Authority in the United Kingdom, and their respective upgrades (NSTX-U and MAST-U) are two MAST fusion devices that have operated roughly over the past two decades. Both devices have made significant contributions to understanding spherical tokamak (ST) plasma physics, and fusion plasmas in general, and both have contributed data to multi-machine database studies. Several diagnostics have been physically moved from one machine to the other by diagnostic teams working on both devices. Collaboration has benefited both research teams in the areas of operational expertise, scenario development, and equilibrium reconstruction techniques. More focused comparative studies between the two devices have been pursued over the years in many areas as well, including stability calculations, disruption characterization, pedestal and edge localized mode stability, confinement and transport, energetic particles, and heating and current drive modelling. Together NSTX/-U and MAST/-U set the stage for the future of STs, which is entering the phase of design of demonstration power plant devices.
The following article is
Open access
Learning time-dependent and integro-differential collision operators from plasma phase space data using differentiable simulators
Diogo D Carvalho
et al
2026
Plasma Phys. Control. Fusion
68
045044
View article
, Learning time-dependent and integro-differential collision operators from plasma phase space data using differentiable simulators
PDF
, Learning time-dependent and integro-differential collision operators from plasma phase space data using differentiable simulators
Collisional and stochastic wave-particle dynamics in plasmas far from equilibrium are complex, temporally evolving, stochastic processes which are challenging to model. In this work, we extend previous methods coupling differentiable kinetic simulators and plasma phase space diagnostics to learn collision operators that account for time-varying background distributions. We also introduce a more general integro-differential operator formulation to probe relevant terms in the collision operator. To validate the proposed methodology we use data generated by self-consistent electromagnetic particle-in-cell simulations. We show that both approaches recover operators that can accurately reproduce the plasma phase space dynamics while being more accurate than estimates based on particle track statistics. These results further demonstrate the potential of using differentiable simulators to infer collision operators for scenarios where no closed form solution exists or deviations from existing theory are expected.
Developing disruption avoidance functions for the ITER plasma control system
P C de Vries
et al
2026
Plasma Phys. Control. Fusion
68
045043
View article
, Developing disruption avoidance functions for the ITER plasma control system
PDF
, Developing disruption avoidance functions for the ITER plasma control system
Disruption avoidance is a key facet of the overall task to manage tokamak disruptions. This paper defines the disruption avoidance function as being a component of the ITER plasma control system (PCS) exception handling. Defining this component of the ITER PCS is essential since its functions require dedicated attention for both design and deployment. This paper aims to bridge the gap between research and development of conceptual functionality and obtaining real-time codes for the ITER PCS that can be confidently deployed during Start of Research Operation—the first campaign to be executed on ITER. The paper provides a first breakdown and design status of specific ITER PCS disruption avoidance functions. The current functional breakdown is compared with various research efforts and functions tested on present tokamaks. This allows the identification of open issues and complications. Possible research studies are identified which will be able to strengthen the preparation of the ITER disruption avoidance functions
prior
to the start first operation.
Dielectric response and structural properties of finite-temperature electron liquids
Chengliang Lin
et al
2026
Plasma Phys. Control. Fusion
68
045042
View article
, Dielectric response and structural properties of finite-temperature electron liquids
PDF
, Dielectric response and structural properties of finite-temperature electron liquids
The dielectric response and structural properties of finite-temperature electron liquids are central to accurately describing the physical behavior of electronic systems. This study presents a robust analytical model for the static structure factor (SSF) of the uniform electron gas, combining physically motivated form for the SSF with constraints derived from high-accuracy path integral Monte Carlo simulations. The model accurately reproduces key features of the SSF across a broad range of temperatures and densities. Using this SSF, the density response function is directly evaluated, enabling a self-consistent definition of the static local field correction. As practical applications, the model is employed to investigate the low-velocity stopping power and the electron–ion friction coefficient. Results derived for the friction coefficient show good agreement with simulation data at moderate coupling and degeneracy. The proposed approach provides a computationally efficient and reliable method for characterizing the static response properties of correlated electron systems, facilitating improved simulations of energy deposition and ionic transport in warm dense matter and other strongly coupled quantum plasmas.
The following article is
Open access
Continuum radiated power density (
) and effective charge (
) estimates from multi-energy photon-counting measurements
Luis F Delgado-Aparicio
et al
2026
Plasma Phys. Control. Fusion
68
045041
View article
, Continuum radiated power density ( ) and effective charge ( ) estimates from multi-energy photon-counting measurements
PDF
, Continuum radiated power density ( ) and effective charge ( ) estimates from multi-energy photon-counting measurements
Multi-energy soft x-ray pinhole cameras have been designed, built, calibrated, and operated at Madison symmetric Torus, Alcator C-Mod, and more recently at Tokamak a configuration variable and Tungsten Environment in Steady-State Tokamak (WEST), to measure plasma emission across multiple energy ranges. Here we describe a new methodology to estimate the local continuum radiated power density and the plasma effective charge (
) directly from photon-counting measurements of the line-free continuum emission (Bremsstrahlung and Radiative Recombination) in several energy bands between 11 and 18 keV. This capability is particularly valuable for confinement systems using metal plasma-facing components, where x-ray losses from interactions with the sputtered wall can represent a significant fraction of the total radiated power (
). The approach leverages a well-characterized detector responsivity, modeled by a complementary error function, and interprets the differential multi-energy measurements between adjacent energy levels through the probability density function of a Gaussian distribution. The implementation of this diagnostic technique is currently under development on the WEST tokamak, aiming at the goal of providing real-time
and
measurements during long-pulse operation (up to 1000 s) in the 2026 campaign.
First 3D plasma transport calculations for the Neutral Beam Test Facility
D López-Bruna
et al
2026
Plasma Phys. Control. Fusion
68
045040
View article
, First 3D plasma transport calculations for the Neutral Beam Test Facility
PDF
, First 3D plasma transport calculations for the Neutral Beam Test Facility
The Neutral Beam Test Facility (NBTF) in Padua, Italy, makes use of large ion sources based on the inductive coupling of radio-frequency (RF) waves with the plasma. Transport modelling provides tools to interpret and guide the experiments towards an efficient plasma heating and control. Although there exist comprehensive 2D fluid transport models assuming axial symmetry, some important features of these large ion sources are intrinsically three-dimensional. Here we present the first 3D numerical calculations, NBTF relevant, of a fluid transport model for the plasma electron density and temperature assuming ambipolar fluxes. The induced plasma current distribution driven by the RF current is evaluated with frequent updates of the absorbed power consistently with the evolving electron density and temperature distributions. Despite the simplicity of the transport model, it shows overall results in fair agreement with the present experimental knowledge. We present scans of the RF power fed to the driver at varying neutral gas pressure and temperature, and driving frequency. First results in presence of a traverse magnetic filter field, a clearly non-axisymmetric ingredient, indicate that previous 2D calculations considering the field either parallel or perpendicular to the calculation domain give acceptable limit cases. All these results set the basis for further studies aimed at helping in the operation and final design of the NBTF devices, which are the pilot plants for the ITER neutral-beam injection system.
The inertial confinement fusion experimental platform and diagnostics for studies of nuclear reactions relevant to nuclear astrophysics
M Gatu Johnson
et al
2026
Plasma Phys. Control. Fusion
68
033001
View article
, The inertial confinement fusion experimental platform and diagnostics for studies of nuclear reactions relevant to nuclear astrophysics
PDF
, The inertial confinement fusion experimental platform and diagnostics for studies of nuclear reactions relevant to nuclear astrophysics
High energy density plasmas generated in laser-driven inertial confinement fusion implosions provide unparalleled laboratory conditions for studying stellar-relevant nuclear reactions: plasma environment; hot and dense; uniquely high achievable neutron flux. These experiments have the potential to address long-standing questions about plasma effects on nuclear reactions hitherto experimentally inaccessible, including nuclear rates with thermally distributed reactants, plasma screening, and reactions involving nuclei in excited states. The National Ignition Facility (NIF) and OMEGA lasers are two primary facilities for executing experiments of this type. Existing and future nuclear diagnostics, along with supporting diagnostics to characterize the platform, enable exploitation of these plasmas for such nuclear astrophysics-relevant experiments. This review describes the nuclear diagnostic capabilities currently available for these types of experiments at the NIF and OMEGA, including neutron time-of-flight spectrometers, charged-particle detectors, gamma detectors and radiochemistry diagnostics, and briefly summarizes other available diagnostic capabilities used for platform characterization. Enabling tools not yet available are also identified, including a rapid radioactive sample retrieval system, a low-energy neutron spectrometer and a high-efficiency gamma spectrometer.
The following article is
Open access
A review of collaborative studies between the NSTX/-U and MAST/-U spherical tokamaks
J W Berkery
et al
2025
Plasma Phys. Control. Fusion
67
053001
View article
, A review of collaborative studies between the NSTX/-U and MAST/-U spherical tokamaks
PDF
, A review of collaborative studies between the NSTX/-U and MAST/-U spherical tokamaks
The National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratory in the United States, and the mega ampere spherical tokamak (MAST) at the United Kingdom Atomic Energy Authority in the United Kingdom, and their respective upgrades (NSTX-U and MAST-U) are two MAST fusion devices that have operated roughly over the past two decades. Both devices have made significant contributions to understanding spherical tokamak (ST) plasma physics, and fusion plasmas in general, and both have contributed data to multi-machine database studies. Several diagnostics have been physically moved from one machine to the other by diagnostic teams working on both devices. Collaboration has benefited both research teams in the areas of operational expertise, scenario development, and equilibrium reconstruction techniques. More focused comparative studies between the two devices have been pursued over the years in many areas as well, including stability calculations, disruption characterization, pedestal and edge localized mode stability, confinement and transport, energetic particles, and heating and current drive modelling. Together NSTX/-U and MAST/-U set the stage for the future of STs, which is entering the phase of design of demonstration power plant devices.
The following article is
Open access
Integrated modelling of tokamak plasmas: progress and challenges towards ITER operation and reactor design
C Bourdelle 2025
Plasma Phys. Control. Fusion
67
043001
View article
, Integrated modelling of tokamak plasmas: progress and challenges towards ITER operation and reactor design
PDF
, Integrated modelling of tokamak plasmas: progress and challenges towards ITER operation and reactor design
In tokamak plasmas, non-linear interplay between transport and sources/sinks takes place for all transported quantities (current, heat, particles and momentum). Thanks to integrated modelling frameworks, we can iterate physics-based quasilinear turbulent transport models over multiple confinement times. Such modelling allows us to predict current, temperature, density and rotation profiles, and to disentangle the causality at play behind the modelled time evolution. An intense validation effort of such modelling against experimental measurements has been ongoing and has progressed our understanding. In dynamical phases, the so-called ‘cold pulse’ physics have been explained in the AUG tokamak, the isotope impact in plasma current ramp-up is understood in the JET tokamak, and the impact of the particle source (from neutral beam injection) on tungsten core accumulation has been clarified in JET and AUG. In stationary phases, the saturation of the ion temperature in electron-heated WEST plasmas has been clarified, and the energy content has been predicted with higher accuracy than empirical scaling laws with respect to the plasma current, magnetic field, plasma size and gas fueling, both in L and H modes on AUG. The validation of physics-based integrated modelling allows control optimisation in preparation for ITER operation as well as risk reduction for the design of future reactors. However, despite the reported progress, physics gaps remain on this path. For example, unlike today’s devices, ITER-class devices will be opaque to neutrals and fuelled by pellets. In the absence of a physical understanding of the transport in the pedestal, extrapolation is uncertain. Moreover, in burning plasmas, the non-linear coupling between the central core profiles and the fusion power is very strong. The uncertainties in profile predictions due to unverified and unvalidated reduced transport models in such high-pressure plasmas lead to uncertain fusion power predictions. Solutions on how to address these challenges within integrated modelling will be proposed.
The following article is
Open access
40 years of JET operations: a unique contribution to fusion science
F G Rimini
et al
2025
Plasma Phys. Control. Fusion
67
033001
View article
, 40 years of JET operations: a unique contribution to fusion science
PDF
, 40 years of JET operations: a unique contribution to fusion science
During its 40 years of operations, the Joint European Torus (JET) tokamak has consistently pushed the physics and engineering boundaries of fusion research, providing the scientific community with a unique testing ground for theories and innovative ideas. This paper covers a selection of remarkable contributions of JET to various fields of tokamak science, from transport and plasma heating studies to plasma-wall interaction and D-T experiments, and their impact on the fusion research progress.
Cross-scale turbulence in space plasmas: old concepts, recent findings, and future challenges
Tommaso Alberti
et al
2025
Plasma Phys. Control. Fusion
67
023001
View article
, Cross-scale turbulence in space plasmas: old concepts, recent findings, and future challenges
PDF
, Cross-scale turbulence in space plasmas: old concepts, recent findings, and future challenges
Turbulence, a fascinating and intricate phenomenon, has captivated scientists over different domains, mainly for its complex cross-scale nature spanning a wide range of temporal and spatial scales. Despite significant advances in theories and observations in the last decades, some aspects of turbulence still remain unsolved, motivating new efforts to understand its underlying physical mechanisms and refine mathematical theories along with numerical models. This topical review explores recent findings from the Parker Solar Probe mission, providing a distinctive opportunity to characterize solar wind features at varying heliocentric distances. Analyzing the radial evolution of magnetic and velocity field fluctuations across the inertial range, a transition has been evidenced from local to global self-similarity as proximity to the Sun increases. This behavior has been reconciled with magnetohydrodynamic theory revising an old concept by emphasizing the evolving nature of the coupling between fields. This offers inspiration for novel modeling approaches to understand open challenges in interplanetary plasma physics as the heating and acceleration of the solar wind, as well as, its evolution within the inner Heliosphere.
The following article is
Open access
Identification of mode numbers and wave numbers by multiple harmonics of instabilities
Hu et al
View accepted manuscript
, Identification of mode numbers and wave numbers by multiple harmonics of instabilities
PDF
, Identification of mode numbers and wave numbers by multiple harmonics of instabilities
Harmonic phenomena of plasma instabilities are frequently observed in tokamak plasmas. The harmonics of instabilities have higher toroidal mode numbers than their base modes, leading to proportionally larger Doppler shifts. This paper presents a method for determining the toroidal mode number based on the frequency differences between harmonics. Based on Doppler shift effect, the toroidal mode number can be expressed as n = (f
-f
)/((l-1)f
vϕ
), where l is the harmonic order and f
vϕ
is the toroidal rotation frequency. Compared to conventional techniques for mode number identification, the proposed approach offers advantages such as simplified data processing and lower requirement for the number of diagnostic channels. The harmonic components in the frequency spectrum can also be used to retrieve the instability frequency in the plasma frame. In this paper, it is demonstrated that the harmonics of plasma instabilities are not generated by intrinsic mode coupling, but are attributed to the nonlinear distortion of waveform. Diagnostic measurements, including soft X-ray and microwave interferometry, confirm that higher-order harmonics of plasma instabilities exist as real structural features inside the plasma and can interact with microwaves when the Bragg condition is satisfied. This property can be utilized to determine the perpendicular wave numbers of the instabilities. A simple physical model of the distribution of an instability and its harmonics is also proposed.
Diffusion wall time in toroidally segmented shell aka Armadillo
Abate et al
View accepted manuscript
, Diffusion wall time in toroidally segmented shell aka Armadillo
PDF
, Diffusion wall time in toroidally segmented shell aka Armadillo
An analytical expression for the diffusion wall time of a toroidally segmented conducting shell (the Armadillo configuration) is derived by extending the continuous-shell formulation to include the non-axisymmetric current pattern imposed by the presence of toroidal gaps. The segmentation constrains the toroidal current to follow a standing-wave structure that vanishes at the gap locations, introducing a correction to the effective resistivity that grows quadratically with the number of gaps and competes with the intrinsic toroidal scale of the mode. As a result, the wall time decreases rapidly for low toroidal-number modes, more gradually for intermediate ones, and only for sufficiently large segmentation in the high-$n$ regime. The analytical formula shows agreement within $10\%$ against 3D electromagnetic numerical calculations. The resulting expression provides a compact tool for estimating the wall time of segmented conducting structures surrounding the plasma, with direct applications to MHD stability and control in both RFPs and tokamaks.
The following article is
Open access
Temporal and spatial evolution of the ion temperature in the WEST tokamak
Forestier-Colleoni et al
View accepted manuscript
, Temporal and spatial evolution of the ion temperature in the WEST tokamak
PDF
, Temporal and spatial evolution of the ion temperature in the WEST tokamak
Understanding ion temperature dynamics is crucial for interpreting energy transport, heating and confinement in magnetically confined plasmas. In the WEST tokamak, ion temperature is typically inferred from neutron flux measurements, which provide reliable global estimates but lack spatial resolution. To overcome this limitation, we employ the X-ray Imaging Crystal Spectrometer (XICS), which allows ion temperature measurements with both temporal and spatial resolution. This paper presents the XICS diagnostic, methods, its capabilities and limitations. As an illustration an analysis of two representative WEST discharges are presented. The first features stationary plasma parameters, highlighting the temporal and spatial evolution of ion temperature profiles along with associated uncertainties. The second involves an X-Point Radiator (XPR) regime, where a sudden increase in ion temperature and profile modification are observed. A comparison with neutron flux measurements demonstrates good agreement, confirming the reliability of XICS and its potential for future experimental campaigns.
The following article is
Open access
Parametric decay instabilities of microwave beams in fusion plasmas: occurrence, consequences and new possibilities
Nielsen et al
View accepted manuscript
, Parametric decay instabilities of microwave beams in fusion plasmas: occurrence, consequences and new possibilities
PDF
, Parametric decay instabilities of microwave beams in fusion plasmas: occurrence, consequences and new possibilities
Electron cyclotron heating by high-power microwave beams is a key method for plasma heating in tokamaks and stellarators. Under some conditions, these beams engage in nonlinear three-wave interactions, known as parametric decay instabilities (PDIs), where energy is transferred from the main beam to two downshifted waves. PDIs are well documented to occur during fundamental electron Bernstein wave heating, with observations in multiple devices. However, PDIs were overlooked in the more common second-harmonic electron cyclotron heating until recently, when nonlinear scattering was observed. This has been attributed to a class of absolute PDIs that involves wave trapping in density fluctuations. Here we provide an overview of recent numerical and experimental results in the study of PDIs. We show direct observations of PDIs at the devices ASDEX Upgrade, TCV, Wendelstein 7-X, and NORTH, and show that the occurrence of PDIs is correlated with density fluctuations in the scrape-off layer caused by ELMs and blobs as well as density fluctuations in the plasma core due to NTMs. We outline the consequences of PDI occurrence, which could include a decrease in heating efficiency and an associated fast-ion production. In addition, we discuss possible schemes for exploiting PDIs, including controlled energy transfer to selected plasma waves and potential diagnostic techniques for density fluctuations.
The following article is
Open access
High-Precision X-ray Metrology and Crystal Calibration with the EXCALIBUR Facility: Advancing Laboratory-Based Diagnostics for Plasma Science
Santana et al
View accepted manuscript
, High-Precision X-ray Metrology and Crystal Calibration with the EXCALIBUR Facility: Advancing Laboratory-Based Diagnostics for Plasma Science
PDF
, High-Precision X-ray Metrology and Crystal Calibration with the EXCALIBUR Facility: Advancing Laboratory-Based Diagnostics for Plasma Science
The EXCALIBUR (Experimental X-ray CALIBration UseR) facility at General Atomics is a versatile x-ray tool supporting diverse research needs not covered by commercial instruments. It enables synchrotron-grade X-ray metrology in a compact, lab-based system. Designed for fast, high-precision measurements, it supports the calibration of X-ray crystals, filters, and target components used in high-energy-density (HED) physics and plasma experiments. EXCALIBUR features a 30kV X-ray tube, NIST calibrated silicon drift detector, X-Ray Cameras, and a suite of automated instruments and analysis scripts. Areal density, opacity, and spectral responses measurements can be completed routinely with the capability to measure matrix of points on a single sample or 10s of samples per day with photon energy range of 1 – 17keV. These measurements have 1% repeatability and ~1-5% accuracy limited by the current opacity databases. EXCALIBUR’s breakthrough capability lies in its ability to calibrate crystals in a benchtop lab-base measurement therefore allowing more accessibility to the community. Crystal calibrations cover photon energies from ~600 eV to 20 keV with ~10% uncertainty. These measurements are essential for the development and validation of experimental plasma diagnostics. Demonstrations involving opacity measurements of Cu-Mg-SiO2 foil, gas cell opacity benchmarks of Argon, and Quartz (Qz) transmission crystals are presented.
More Accepted manuscripts
The following article is
Open access
Learning time-dependent and integro-differential collision operators from plasma phase space data using differentiable simulators
Diogo D Carvalho
et al
2026
Plasma Phys. Control. Fusion
68
045044
View article
, Learning time-dependent and integro-differential collision operators from plasma phase space data using differentiable simulators
PDF
, Learning time-dependent and integro-differential collision operators from plasma phase space data using differentiable simulators
Collisional and stochastic wave-particle dynamics in plasmas far from equilibrium are complex, temporally evolving, stochastic processes which are challenging to model. In this work, we extend previous methods coupling differentiable kinetic simulators and plasma phase space diagnostics to learn collision operators that account for time-varying background distributions. We also introduce a more general integro-differential operator formulation to probe relevant terms in the collision operator. To validate the proposed methodology we use data generated by self-consistent electromagnetic particle-in-cell simulations. We show that both approaches recover operators that can accurately reproduce the plasma phase space dynamics while being more accurate than estimates based on particle track statistics. These results further demonstrate the potential of using differentiable simulators to infer collision operators for scenarios where no closed form solution exists or deviations from existing theory are expected.
The following article is
Open access
Continuum radiated power density (
) and effective charge (
) estimates from multi-energy photon-counting measurements
Luis F Delgado-Aparicio
et al
2026
Plasma Phys. Control. Fusion
68
045041
View article
, Continuum radiated power density ( ) and effective charge ( ) estimates from multi-energy photon-counting measurements
PDF
, Continuum radiated power density ( ) and effective charge ( ) estimates from multi-energy photon-counting measurements
Multi-energy soft x-ray pinhole cameras have been designed, built, calibrated, and operated at Madison symmetric Torus, Alcator C-Mod, and more recently at Tokamak a configuration variable and Tungsten Environment in Steady-State Tokamak (WEST), to measure plasma emission across multiple energy ranges. Here we describe a new methodology to estimate the local continuum radiated power density and the plasma effective charge (
) directly from photon-counting measurements of the line-free continuum emission (Bremsstrahlung and Radiative Recombination) in several energy bands between 11 and 18 keV. This capability is particularly valuable for confinement systems using metal plasma-facing components, where x-ray losses from interactions with the sputtered wall can represent a significant fraction of the total radiated power (
). The approach leverages a well-characterized detector responsivity, modeled by a complementary error function, and interprets the differential multi-energy measurements between adjacent energy levels through the probability density function of a Gaussian distribution. The implementation of this diagnostic technique is currently under development on the WEST tokamak, aiming at the goal of providing real-time
and
measurements during long-pulse operation (up to 1000 s) in the 2026 campaign.
The following article is
Open access
Identification of mode numbers and wave numbers by multiple harmonics of instabilities
Liwen Hu
et al
2026
Plasma Phys. Control. Fusion
View article
, Identification of mode numbers and wave numbers by multiple harmonics of instabilities
PDF
, Identification of mode numbers and wave numbers by multiple harmonics of instabilities
Harmonic phenomena of plasma instabilities are frequently observed in tokamak plasmas. The harmonics of instabilities have higher toroidal mode numbers than their base modes, leading to proportionally larger Doppler shifts. This paper presents a method for determining the toroidal mode number based on the frequency differences between harmonics. Based on Doppler shift effect, the toroidal mode number can be expressed as n = (f
-f
)/((l-1)f
vϕ
), where l is the harmonic order and f
vϕ
is the toroidal rotation frequency. Compared to conventional techniques for mode number identification, the proposed approach offers advantages such as simplified data processing and lower requirement for the number of diagnostic channels. The harmonic components in the frequency spectrum can also be used to retrieve the instability frequency in the plasma frame. In this paper, it is demonstrated that the harmonics of plasma instabilities are not generated by intrinsic mode coupling, but are attributed to the nonlinear distortion of waveform. Diagnostic measurements, including soft X-ray and microwave interferometry, confirm that higher-order harmonics of plasma instabilities exist as real structural features inside the plasma and can interact with microwaves when the Bragg condition is satisfied. This property can be utilized to determine the perpendicular wave numbers of the instabilities. A simple physical model of the distribution of an instability and its harmonics is also proposed.
The following article is
Open access
Radial impurity transport in the pedestal of ASDEX Upgrade plasmas in H-mode, L-mode, and the QCE regime
T Gleiter
et al
2026
Plasma Phys. Control. Fusion
68
045037
View article
, Radial impurity transport in the pedestal of ASDEX Upgrade plasmas in H-mode, L-mode, and the QCE regime
PDF
, Radial impurity transport in the pedestal of ASDEX Upgrade plasmas in H-mode, L-mode, and the QCE regime
We present an experimental study of radial impurity transport in the pedestal, comparing ASDEX Upgrade discharges across different operation regimes. The analyses employ our recently developed framework that extracts flux surface-averaged diffusion and convection profiles from the stationary balance of multiple impurity charge state densities. High radial resolution and rigorous uncertainty quantification are achieved through a customized diagnostic setup of the charge-exchange spectroscopy and with Bayesian sampling to solve the complex inverse problem. For optimal diagnostic feasibility the presented study focuses on neon transport. Dedicated discharges were performed with neon puffing in high confinement mode (H-mode) with large, type-I, edge localized modes (ELMs), in low confinement mode (L-mode), and in the quasi-continuous exhaust (QCE) regime. The inferred transport coefficients are compared with neoclassical modeling to disentangle collisional and anomalous contributions. Our results validate previous findings of predominantly neoclassical impurity transport between type-I ELMs, caused by the turbulence suppressing edge transport barrier in the H-mode pedestal. We also recover the expected strong turbulent impurity diffusion in the L-mode edge, and qualitatively confirm that large ELMs act on impurities as additional diffusion. The QCE regime is a promising confinement scenario for future reactors due to the absence of large ELMs in combination with high separatrix densities. Its pedestal dynamics are modified by the presence of small, type-II, ELMs together with a quasi-coherent mode. Their impact on impurity transport is quantified as significant anomalous diffusion in the pedestal, leading to weaker impurity density gradients.
The following article is
Open access
Ultralow-emittance electron beams from laser wakefield accelerator based on sharp density transition injection
Yanjie Ge
et al
2026
Plasma Phys. Control. Fusion
68
045036
View article
, Ultralow-emittance electron beams from laser wakefield accelerator based on sharp density transition injection
PDF
, Ultralow-emittance electron beams from laser wakefield accelerator based on sharp density transition injection
We numerically investigate a scheme for generating ultralow-emittance electron beams using hydrodynamic optical-field-ionization (HOFI)-induced shock injection in laser wakefield acceleration (LWFA). A steep density down-ramp formed by the HOFI process enables electron injection at low laser amplitude
, reducing transverse forces and favoring longitudinal injection to minimize the beam emittance. Particle-in-cell simulations demonstrate the production of high-quality electron beams with a charge of
, an energy of approximately
, an rms energy spread of about 3%, and a normalized projected emittance of about
. Unlike mechanically driven shocks commonly used in LWFA, the HOFI-induced shock exhibits superior stability, enabling precise control over the electron injection process. Moreover, because injection occurs where
is relatively low and slowly varying, the scheme shows enhanced tolerance to laser energy jitter. This approach provides a promising pathway for generating high-quality electron beams suited for downstream applications such as GeV-class plasma accelerators and free-electron lasers.
The following article is
Open access
Developing an automated fluid activation residence time CFD database
L R Humphrey
et al
2026
Plasma Phys. Control. Fusion
68
045035
View article
, Developing an automated fluid activation residence time CFD database
PDF
, Developing an automated fluid activation residence time CFD database
Fluid activation is of critical importance to fusion power plant design, as it impacts dose rates to maintenance personnel and equipment, heating in sensitive components, and radionuclide inventories with implications for accident scenarios and waste. The levels of fluid activation in a system are dependent on the neutron flux spectrum and the exposure time of the fluid. Accurately modelling the fluid irradiation history for a pipe system requires computational fluid dynamics (CFD) to determine the residence time distribution (RTD) of fluid particles passing through each component. However, performing CFD on whole pipe systems can be computationally expensive which limits frequency of design iterations.
To address this concern, a new code was developed: FARBASE (the Fluid Activation Residence time dataBASE). This paper details the development and functionality of FARBASE, focusing on its two key features:
An automated CFD pipeline which accepts a parametric description of a pipe component under given flow conditions, generates the pipe geometry, runs a steady-state OpenFOAM simulation, and returns the resulting RTD.
A Gaussian process regression (GPR) surrogate model which can be trained on the CFD database and queried to provide uncertainty quantified predictions of RTDs. Where the uncertainty of the GPR prediction exceeds a given threshold, FARBASE can automatically perform additional CFD to update the database, improving the accuracy of future predictions.
Work is ongoing to utilise FARBASE in UKAEA’s GammaFlow fluid activation code, providing RTDs which are used to determine the production and decay rates of key radionuclides in each component of a basic water circuit. This will be extended in future to model benchmark experiments and validate the combined tool, which aims to provide an efficient and standardised approach to modelling activation in complex fluid circuits.
The following article is
Open access
Instrumented high fluence neutron irradiation test of antimony Hall sensors
M Ivanek
et al
2026
Plasma Phys. Control. Fusion
68
045034
View article
, Instrumented high fluence neutron irradiation test of antimony Hall sensors
PDF
, Instrumented high fluence neutron irradiation test of antimony Hall sensors
Hall sensors based on antimony sensitive layer will be installed on ITER within the system of outer vessel steady-state magnetic field sensors and they are also considered for deployment on future European demonstration fusion power reactor (EU-DEMO). The role of these sensors will be to contribute to determination of the key tokamak plasma parameters such as the plasma position, shape, and plasma current. This paper presents the design of an instrumented high fluence neutron irradiation experiment, where antimony Hall sensors are exposed to the neutron and gamma radiation of the LVR-15 research reactor core (10 MW thermal). The goal of this experiment is to qualify the antimony Hall sensors for use on the EU-DEMO reactor. Initial results from the first phase of the experiment where the sensors were exposed to the fast neutron fluence (
0.1 MeV) of 1.4 × 10
20
cm
−2
are reported.
The following article is
Open access
Temporal and spatial evolution of the ion temperature in the WEST tokamak
Pierre Forestier-Colleoni
et al
2026
Plasma Phys. Control. Fusion
View article
, Temporal and spatial evolution of the ion temperature in the WEST tokamak
PDF
, Temporal and spatial evolution of the ion temperature in the WEST tokamak
Understanding ion temperature dynamics is crucial for interpreting energy transport, heating and confinement in magnetically confined plasmas. In the WEST tokamak, ion temperature is typically inferred from neutron flux measurements, which provide reliable global estimates but lack spatial resolution. To overcome this limitation, we employ the X-ray Imaging Crystal Spectrometer (XICS), which allows ion temperature measurements with both temporal and spatial resolution. This paper presents the XICS diagnostic, methods, its capabilities and limitations. As an illustration an analysis of two representative WEST discharges are presented. The first features stationary plasma parameters, highlighting the temporal and spatial evolution of ion temperature profiles along with associated uncertainties. The second involves an X-Point Radiator (XPR) regime, where a sudden increase in ion temperature and profile modification are observed. A comparison with neutron flux measurements demonstrates good agreement, confirming the reliability of XICS and its potential for future experimental campaigns.
The following article is
Open access
Parametric decay instabilities of microwave beams in fusion plasmas: occurrence, consequences and new possibilities
S Kragh Nielsen
et al
2026
Plasma Phys. Control. Fusion
View article
, Parametric decay instabilities of microwave beams in fusion plasmas: occurrence, consequences and new possibilities
PDF
, Parametric decay instabilities of microwave beams in fusion plasmas: occurrence, consequences and new possibilities
Electron cyclotron heating by high-power microwave beams is a key method for plasma heating in tokamaks and stellarators. Under some conditions, these beams engage in nonlinear three-wave interactions, known as parametric decay instabilities (PDIs), where energy is transferred from the main beam to two downshifted waves. PDIs are well documented to occur during fundamental electron Bernstein wave heating, with observations in multiple devices. However, PDIs were overlooked in the more common second-harmonic electron cyclotron heating until recently, when nonlinear scattering was observed. This has been attributed to a class of absolute PDIs that involves wave trapping in density fluctuations. Here we provide an overview of recent numerical and experimental results in the study of PDIs. We show direct observations of PDIs at the devices ASDEX Upgrade, TCV, Wendelstein 7-X, and NORTH, and show that the occurrence of PDIs is correlated with density fluctuations in the scrape-off layer caused by ELMs and blobs as well as density fluctuations in the plasma core due to NTMs. We outline the consequences of PDI occurrence, which could include a decrease in heating efficiency and an associated fast-ion production. In addition, we discuss possible schemes for exploiting PDIs, including controlled energy transfer to selected plasma waves and potential diagnostic techniques for density fluctuations.
The following article is
Open access
The impact of non-local fluid models on 1D impurity driven detachment in an ITER-like SOL
J L Baker
et al
2026
Plasma Phys. Control. Fusion
68
045032
View article
, The impact of non-local fluid models on 1D impurity driven detachment in an ITER-like SOL
PDF
, The impact of non-local fluid models on 1D impurity driven detachment in an ITER-like SOL
Understanding parallel thermal transport in the scrape-off layer (SOL) is crucial for designing future high-powered tokamak exhaust systems. Fluid models, whilst computationally efficient, cannot accurately predict heat flux in conditions with large temperature gradients or low upstream collisionality. Here the electron mean free path becomes large and so the heat transport is non-local. The impact of non-local electron thermal transport on key detachment processes is often overlooked. The Hermes-3 multi-fluid SOL code is applied to a medium collisionality (
upstream) ITER-like scenario in 1D, comparing non-local Schurtz, Nicolaï, and Busquet (SNB), to classical Spitzer–Härm (SH) as well as flux-limited (FL) electron conduction models. A neon fixed-fraction impurity seeding model is applied at increasing percentage until detachment is observed. Competing behaviour between FL and impurity seeding on target temperatures is observed, whilst the SNB model agrees qualitatively with SH, showing earlier detachment onset compared to FL (at
lower neon fraction). This motivates the inclusion of non-local thermal conduction models (such as the SNB model) in fluid detachment modelling of SOL plasmas.
More Open Access articles
The following article is
Open access
Contemporary particle-in-cell approach to laser-plasma modelling
T D Arber
et al
2015
Plasma Phys. Control. Fusion
57
113001
View article
, Contemporary particle-in-cell approach to laser-plasma modelling
PDF
, Contemporary particle-in-cell approach to laser-plasma modelling
Particle-in-cell (PIC) methods have a long history in the study of laser-plasma interactions. Early electromagnetic codes used the Yee staggered grid for field variables combined with a leapfrog EM-field update and the Boris algorithm for particle pushing. The general properties of such schemes are well documented. Modern PIC codes tend to add to these high-order shape functions for particles, Poisson preserving field updates, collisions, ionisation, a hybrid scheme for solid density and high-field QED effects. In addition to these physics packages, the increase in computing power now allows simulations with real mass ratios, full 3D dynamics and multi-speckle interaction. This paper presents a review of the core algorithms used in current laser-plasma specific PIC codes. Also reported are estimates of self-heating rates, convergence of collisional routines and test of ionisation models which are not readily available elsewhere. Having reviewed the status of PIC algorithms we present a summary of recent applications of such codes in laser-plasma physics, concentrating on SRS, short-pulse laser-solid interactions, fast-electron transport, and QED effects.
Zonal flows in plasma—a review
P H Diamond
et al
2005
Plasma Phys. Control. Fusion
47
R35
View article
, Zonal flows in plasma—a review
PDF
, Zonal flows in plasma—a review
A comprehensive review of zonal flow phenomena in plasmas is presented. While the emphasis is on zonal flows in laboratory plasmas, planetary zonal flows are discussed as well. The review presents the status of theory, numerical simulation and experiments relevant to zonal flows. The emphasis is on developing an integrated understanding of the dynamics of drift wave–zonal flow turbulence by combining detailed studies of the generation of zonal flows by drift waves, the back-interaction of zonal flows on the drift waves, and the various feedback loops by which the system regulates and organizes itself. The implications of zonal flow phenomena for confinement in, and the phenomena of fusion devices are discussed. Special attention is given to the comparison of experiment with theory and to identifying directions for progress in future research.
Density limits in toroidal plasmas
Martin Greenwald 2002
Plasma Phys. Control. Fusion
44
R27
View article
, Density limits in toroidal plasmas
PDF
, Density limits in toroidal plasmas
In addition to the operational limits imposed by MHD stability on plasma current and pressure, an independent limit on plasma density is observed in confined toroidal plasmas. This review attempts to summarize recent work on the phenomenology and physics of the density limit. Perhaps the most surprising result is that all of the toroidal confinement devices considered operate in similar ranges of (suitably normalized) densities. The empirical scalings derived independently for tokamaks and reversed-field pinches are essentially identical, while stellarators appear to operate at somewhat higher densities with a different scaling. Dedicated density limit experiments have not been carried out for spheromaks and field-reversed configurations, however, `optimized' discharges in these devices are also well characterized by the same empirical law. In tokamaks, where the most extensive studies have been conducted, there is strong evidence linking the limit to physics near the plasma boundary: thus, it is possible to extend the operational range for line-averaged density by operating with peaked density profiles. Additional particles in the plasma core apparently have no effect on density limit physics. While there is no widely accepted, first principles model for the density limit, research in this area has focussed on mechanisms which lead to strong edge cooling. Theoretical work has concentrated on the consequences of increased impurity radiation which may dominate power balance at high densities and low temperatures. These theories are not entirely satisfactory as they require assumptions about edge transport and make predictions for power and impurity scaling that may not be consistent with experimental results. A separate thread of research looks for the cause in collisionality enhanced turbulent transport. While there is experimental and theoretical support for this approach, understanding of the underlying mechanisms is only at a rudimentary stage and no predictive capability is yet available.
The following article is
Open access
Impurity transport in tokamak plasmas, theory, modelling and comparison with experiments
Clemente Angioni 2021
Plasma Phys. Control. Fusion
63
073001
View article
, Impurity transport in tokamak plasmas, theory, modelling and comparison with experiments
PDF
, Impurity transport in tokamak plasmas, theory, modelling and comparison with experiments
In this paper, the theory of collisional and turbulent transport of impurities in tokamak plasmas is reviewed. The results are presented with the aim of providing at the same time a historical reconstruction of the scientific progress and a complete description of the present theoretical knowledge, with a hopefully sufficiently complete reference to the works which have been published in the field in the last decades. After a general introduction on the physics challenges offered by the problem of impurity transport and their relevance for practical nuclear fusion energy, the theory of collisional transport is presented. Here a specific section is also dedicated to the transport parallel to the magnetic field lines. A complete review of the transport mechanisms produced by turbulence follows. The corresponding comparisons between theoretical predictions and experimental observations are also presented, highlighting the influence that the validation activities had in motivating further theoretical investigations. The paper is completed by a section on the direct interactions between collisional and turbulent transport and by a final specific review dedicated to the progress in the theory–based modelling activities. In the writing of this review paper, the main goal has been to combine readability with completeness and scientific rigour, providing a comprehensive list of references for deeper documentation on specific aspects.
Particle simulation of plasmas: review and advances
J P Verboncoeur 2005
Plasma Phys. Control. Fusion
47
A231
View article
, Particle simulation of plasmas: review and advances
PDF
, Particle simulation of plasmas: review and advances
Particle simulation of plasmas, employed since the 1960s, provides a self-consistent, fully kinetic representation of general plasmas. Early incarnations looked for fundamental plasma effects in one-dimensional systems with ∼10
–10
particles in periodic electrostatic systems on computers with ≲100 kB memory. Recent advances model boundary conditions, such as external circuits to wave launchers, collisions and effects of particle–surface impact, all in fully relativistic three-dimensional electromagnetic systems using ∼10
–10
10
particles on massively parallel computers. While particle codes still enjoy prominance in a number of basic physics areas, they are now often used for engineering devices as well.
Plasma medicine—current state of research and medical application
K-D Weltmann and Th von Woedtke 2017
Plasma Phys. Control. Fusion
59
014031
View article
, Plasma medicine—current state of research and medical application
PDF
, Plasma medicine—current state of research and medical application
Plasma medicine means the direct application of cold atmospheric plasma (CAP) on or in the human body for therapeutic purposes. Further, the field interacts strongly with results gained for biological decontamination. Experimental research as well as first practical application is realized using two basic principles of CAP sources: dielectric barrier discharges (DBD) and atmospheric pressure plasma jets (APPJ). Originating from the fundamental insights that the biological effects of CAP are most probably caused by changes of the liquid environment of cells, and are dominated by reactive oxygen and nitrogen species (ROS, RNS), basic mechanisms of biological plasma activity are identified. It was demonstrated that there is no increased risk of cold plasma application and, above all, there are no indications for genotoxic effects. The most important biological effects of cold atmospheric pressure plasma were identified: (1) inactivation of a broad spectrum of microorganisms including multidrug resistant ones; (2) stimulation of cell proliferation and tissue regeneration with lower plasma treatment intensity (treatment time); (3) inactivation of cells by initialization of programmed cell death (apoptosis) with higher plasma treatment intensity (treatment time). In recent years, the main focus of clinical applications was in the field of wound healing and treatment of infective skin diseases. First CAP sources are CE-certified as medical devices now which is the main precondition to start the introduction of plasma medicine into clinical reality. Plasma application in dentistry and, above all, CAP use for cancer treatment are becoming more and more important research fields in plasma medicine. A further in-depth knowledge of control and adaptation of plasma parameters and plasma geometries is needed to obtain suitable and reliable plasma sources for the different therapeutic indications and to open up new fields of medical application.
Kinetic calculation of neoclassical transport including self-consistent electron and impurity dynamics
E A Belli and J Candy 2008
Plasma Phys. Control. Fusion
50
095010
View article
, Kinetic calculation of neoclassical transport including self-consistent electron and impurity dynamics
PDF
, Kinetic calculation of neoclassical transport including self-consistent electron and impurity dynamics
Numerical studies of neoclassical transport, beginning with the fundamental drift-kinetic equation (DKE), have been extended to include the self-consistent coupling of electrons and multiple ion species. The code, NEO, provides a first-principles based calculation of the neoclassical transport coefficients directly from solution of the distribution function by solving a hierarchy of equations derived by expanding the DKE in powers of ρ
, the ratio of the ion gyroradius to system size. This includes the calculation of the first-order electrostatic potential via the Poisson equation, although this potential has exactly no effect on the steady-state transport. Systematic calculations of the second-order particle and energy fluxes and first-order plasma flows and bootstrap current and comparisons with existing theories are given for multi-species plasmas. The ambipolar relation ∑
= 0, which can only be maintained with complete cross-species collisional coupling, is confirmed, and finite mass-ratio corrections due to the collisional coupling are identified. The effects of plasma shaping are also explored, including a discussion of how analytic formulae obtained for circular plasmas (i.e. Chang–Hinton) should be applied to shaped cases. Finite-orbit-width effects are studied via solution of the higher-order DKEs and the implications of non-local transport on the validity of the δ
formulation are discussed.
The ITER design
R Aymar
et al
2002
Plasma Phys. Control. Fusion
44
519
View article
, The ITER design
PDF
, The ITER design
In 1998, after six years of joint work originally foreseen
under the ITER engineering design activities (EDA) agreement,
a design for ITER had been developed fulfilling all objectives and the cost target adopted by the ITER parties in
1992 at the start of the EDA. While accepting this design, the ITER parties
recognized the possibility that they might be unable, for financial reasons,
to proceed to the construction of the then foreseen device. The focus of
effort in the ITER EDA since 1998 has been the development of a new design to meet revised technical objectives and a
cost reduction target of about 50% of the previously accepted cost
estimate. The rationale for the choice of parameters of the design has been
based largely on system analysis drawing on the design solutions already
developed and using the latest physics results and outputs from technology
R&D projects. In so doing the joint central team and home teams converge
towards a new design which will allow the exploration of a range of burning
plasma conditions. The new ITER design, whilst having reduced technical
objectives from its predecessor, will nonetheless meet the programmatic
objective of providing an integrated demonstration of the scientific and
technological feasibility of fusion energy. Background, design features,
performance, safety features, and R&D and future perspectives of the ITER design are discussed.
Applications of laser wakefield accelerator-based light sources
Félicie Albert and Alec G R Thomas 2016
Plasma Phys. Control. Fusion
58
103001
View article
, Applications of laser wakefield accelerator-based light sources
PDF
, Applications of laser wakefield accelerator-based light sources
Laser-wakefield accelerators (LWFAs) were proposed more than three decades ago, and while they promise to deliver compact, high energy particle accelerators, they will also provide the scientific community with novel light sources. In a LWFA, where an intense laser pulse focused onto a plasma forms an electromagnetic wave in its wake, electrons can be trapped and are now routinely accelerated to GeV energies. From terahertz radiation to gamma-rays, this article reviews light sources from relativistic electrons produced by LWFAs, and discusses their potential applications. Betatron motion, Compton scattering and undulators respectively produce x-rays or gamma-rays by oscillating relativistic electrons in the wakefield behind the laser pulse, a counter-propagating laser field, or a magnetic undulator. Other LWFA-based light sources include bremsstrahlung and terahertz radiation. We first evaluate the performance of each of these light sources, and compare them with more conventional approaches, including radio frequency accelerators or other laser-driven sources. We have then identified applications, which we discuss in details, in a broad range of fields: medical and biological applications, military, defense and industrial applications, and condensed matter and high energy density science.
Plasma detachment in divertor tokamaks
A W Leonard 2018
Plasma Phys. Control. Fusion
60
044001
View article
, Plasma detachment in divertor tokamaks
PDF
, Plasma detachment in divertor tokamaks
Observations of divertor plasma detachment in tokamaks are reviewed. Plasma detachment is characterized in terms of transport and dissipation of power, momentum and particle flux along the open field lines from the midplane to the divertor. Asymmetries in detachment onset and other characteristics between the inboard and outboard divertor plasmas is found to be primarily driven by plasma
drifts. The effect of divertor plate geometry and magnetic configuration on divertor detachment is summarized. Control of divertor detachment has progressed with a development of a number of diagnostics to characterize the detached state in real-time. Finally the compatibility of detached divertor operation with high performance core plasmas is examined.
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1984-present
Plasma Physics and Controlled Fusion
doi: 10.1088/issn.0741-3335
Online ISSN: 1361-6587
Print ISSN: 0741-3335
Journal history
1984-present
Plasma Physics and Controlled Fusion
1967-1983
Plasma Physics
1959-1966
Journal of Nuclear Energy. Part C, Plasma Physics, Accelerators, Thermonuclear Research