Equilibrium Gradient Effects in the Theory of Alfven-Wave Heating

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

The Swiss Plasma Center is upgrading the TCV tokamak to test a tightly baffled, long-legged divertor (TBLLD), a novel concept that promises to enhance power exhaust capabilities with minimal modification to the magnetic configuration [1,2]. Simulations using the SOLPS-ITER code indicate that a TBLLD can improve TCV’s power exhaust capability by an order of magnitude compared to the unbaffled configuration [2]. Tight baffling sustains a high poloidal neutral density gradient, thereby, increasing the neutral

The EC Upper Launcher (UL) and Ex-vessel waveguide (EW) are integral components of the ITER Electron Cyclotron (EC) system [1], which plays a key role in achieving and maintaining the high temperatures required for nuclear fusion within the tokamak, providing plasma heating and current drive, and magnetohydrodynamics (MHD) stabilization, which are crucial for ITER’s operational success. The EC system is increasingly becoming the reference mechanism for plasma heating in both present and future devices. Nota

Machine learning (ML)-driven reduced-order modelling is applied to accelerate steady-state convergence in three-dimensional, nonlinear, flux-driven two-fluid simulations of boundary plasma turbulence. A parametric scan of plasma resistivity, heating and density sources is performed to generate comprehensive datasets across various turbulent regimes for model training and validation. To efficiently manage and interpret these datasets, we apply the proper orthogonal decomposition technique to reduce the dimen

Screening of high-Z (W) impurities from the confined plasma by the temperature gradient at the plasma periphery of fusion-grade H-mode plasmas was demonstrated for the first time in JET with the Be/W wall (Field et al 2023 Nucl. Fusion 63 016028). Additional experiments have been performed in JET during 2023, including in deuterium-tritium (DT) during the DTE3 campaign, to further optimise the impurity screening in such plasmas, as well as our bolometric measurements of the W impurity fluxes between and dur

JT-60SA is the world’s largest superconducting tokamak in operation jointly built and exploited by Europe and Japan in the framework of the Broader Approach. JT-60SA aims at addressing some of the technological and physics challenges, such as the long pulse steady-state plasma operation at high beta. The start-up of JT-60SA, which culminated in the first JT-60SA plasma achieved on 23 October 2023 and Operation-1 (OP-1) until the end of 2023, including the achievement of >1 MA diverted plasmas, paves the way

In a recent paper Kirtley and Milroy [D. Kirtley, R. Milroy, J. of Fusion Energy (2023) 42:30] discuss the Helion concept for a pulsed reactor, in which two supersonic field-reversed configurations (FRCs) merge and the resulting plasmoid is adiabatically compressed to fusion conditions. Using D-He3 as fuel this would allow for efficient electromagnetic energy conversion during the subsequent expansion phase. Essential for their very promising projections of energy gain is the assumed large temperature ratio

This contribution will present a feasibility study and conceptual design of a tangential phase-contrast imaging (PCI) diagnostic for the new JT60SA tokamak. PCI is a well-known technique for measuring density fluctuations. Tangential launching, combined with an appropriate spatial filtering technique, affords the measurement highly improved spatial localization, as demonstrated in particular on the TCV tokamak. Tangential ports of 20cm diameter are envisioned to be used on JT60SA, obviating the need to moun

The most classic approach to the dynamics of an n-dimensional mechanical system constrained by d independent holonomic constraints is to pick explicitly a new set of (n - d) curvilinear coordinatesparametrizingthe manifold of configurations satisfying the constraints, and to compute the Lagrangian generating the unconstrained dynamics in these (n - d) configuration coordinates. Starting from this Lagrangian an unconstrained Hamiltonian H(q,p) on 2(n-d) dimensional phase space can then typically be defined i

A detailed study of the operational capabilities of the W7-X/1MW gyrotron operated at 126GHz/TE26,7 is presented. This study is associated with the foreseen upgrade of TCV in which it is planned to add to the present EC system 3MW of additional RF power bringing the total EC-power to 7.5MW. This study is extended to a possible operation of the gyrotron at the ITER relevant frequency of 168GHz in the TE35,9 mode without implementing any further modification neither in the gyrotron nor in the gyrotron superco

In the search of a fusion reactor using magnetic confinement of toroidal plasmas, many important plasma performance parameters directly depend on the shape of the plasma cross-section. The unique shaping capability of the TCV tokamak ("Tokamak à Configuration Variable") has been exploited to study different aspects of tokamak transport and stability, in which the plasma shape may play a role. This presentation will focus on the effects of plasma shape on transport. The TCV tokamak has produced a host of phy

The existence of a critical pressure gradient needed to drive the interchange instability is experimentally demonstrated in the simple magnetized torus TORoidal Plasma EXperiment [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)]. This gradient is reached during a scan in the neutral gas pressure pn. Around a critical value for pn, depending on the magnetic configuration and on the injected rf power, a small increase in the neutral gas pressure triggers a transition in the plasma behavior. The pressure pro

The main objective of the ITER ECRH Upper Launcher (UL) is to control magnetohydrodynamic (MHD) activity: sawtooth oscillations and neoclassical tearing modes. 170GHz RF beams are oriented and focused to obtain a maximum overlapping of the waists of all the beams throughout the deposition location range in the plasma. The steering of the beams is done using 8 independent steering mirrors (SM) placed in the front par t of each one of the four dedicated por t plugs. Accurate and rapid control of the SMs for d

In burning plasma experiments, the very energetic alpha (alpha) particles resulting from a deuterium-tritium fusion reaction will be the dominant heating mechanism and will give rise to new physics issues. Recent experiments performed on the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] and aiming to investigate burning plasma physics are reported in this paper. In the presence of very energetic particles, the magnetohydrodynamic stability of plasmas is affected. Sawteeth

Compact optimized stellarators offer novel solutions for confining high-beta plasmas and developing magnetic confinement fusion. The three-dimensional plasma shape can be designed to enhance the magnetohydrodynamic (MHD) stability without feedback or nearby conducting structures and provide drift-orbit confinement similar to tokamaks. These configurations offer the possibility of combining the steady-state low-recirculating power, external control, and disruption resilience of previous stellarators with the

The modelling of Alfvenic instabilities is discussed from the point of view of mode-conversion, showing how the development of the theory affects the predictions as the limitations of the models are gradually relaxed. Conventional tokamak plasmas are relatively well understood and are used for the case of a kinetic Alfven eigenmode (AE) to assess the resonant wave-particle interactions along the magnetic field. The large safety factor in the core of deeply reversed shear plasmas and the low magnetic field o

The highest volume averaged beta values beta (t) of 2.2% at B-t = 0.75 T (gas puff) and 2.4% at D-t = 1.3 T (pellet) in helical devices have been achieved in LHD. The beta (t) dependence of MHD activities has been investigated in NBI plasmas. The n/m = 1/2 mode, excited in the core region, and the t = 1 resonant modes, in the peripheral region, have been observed. Both of the fluctuation amplitudes increase with beta (t) and pressure gradient. The strong n/m = 1/2 mode, which affects the plasma profile., ha

The TCV tokamak (B-T < 1.5 T, R approximate to 0.88 m, a < 0.25 m) has produced a wide variety of plasma configurations, both diverted and limited, with elongations kappa(a), ranging from 0.9 to 2.58, triangularities delta(a) from -0.7 to 1 as well as discharges with nearly rectangular cross sections. Plasma currents of 1 MA have been obtained in elongated discharges (kappa(a) approximate to 2.3). Ohmic discharges with delta(a) < 0 have smaller sawteeth and higher levels of MHD mode activity than plasmas wi

Due to its pulsed operation mode, a fusion device will have to sustain thermal stresses and at the same time be exposed to a flux of 14 MeV neutrons. In order to simulate this irradiation condition, a new irradiation device has been developed, in which the specimen can be stress and strain-controlled during the irradiation. For the simulation of the fusion neutrons, a 590 MeV proton beam is used. This type of particle produces from spallation reactions the displacement damage and the helium typical of fusio

Equilibrium Gradient Effects in the Theory of Alfven-Wave Heating

Chat with Graph Search

Assessing the Tightly-Baffled, Long-Legged Divertor (TBLLD) concept in TCV

The design of the EC Upper Launcher and Ex-vessel waveguide systems for ITER

Data-driven Model Order Reduction for Accelerating Boundary Plasma Turbulence Simulations

Optimised 'hybrid' Scenario H-mode Plasmas for W Radiation Control in Jet with the Be/w Wall

Overview of first JT-60SA plasma operation and plans in view of ITER and DEMO

Comments on the Paper “Fundamental Scaling of Adiabatic Compression of Field Reversed Configuration Thermonuclear Fusion Plasmas”

Tangential phase-contrast imaging for fluctuation measurements in JT–60SA: a conceptual study

Ambient space formulations and statistical mechanics of holonomically constrained Langevin systems

Design studies of the dual-frequency operation of the W7-X/140GHz/1MW gyrotron at 126GHz for TCV and 168GHz for ITER

Physics Insight from Plasma Shaping of TCV Tokamak Plasmas - focus on Electron Heat Transport

Observation of a critical pressure gradient for the stabilization of interchange modes in simple magnetized toroidal plasmas

Progress on the ITER Upper Launcher Control Systems

Studies of burning plasma physics in the Joint European Torus

Physics of the compact advanced stellarator NCSX

Gyrokinetic modelling of macro-instabilities in high performance tokamak plasmas

MHD characteristics in the high beta regime of the Large Helical Device

Effect of plasma shape on confinement and MHD behaviour in TCV

In-Beam Fatigue of a Ferritic-Martensitic Steel - First Results