Concept

Magnetic diffusion

Related publications (25)

Core MHD instabilities and their spectra in advanced tokamak regimes: ideal and resistive physics

Advanced tokamak regimes, featuring extended regions of low magnetic shear, are promising candidates for future fusion reactors (record breaking DT pulses at JET in hybrid mode) but are also more prone to specific MHD instabilities. The proximity to a rational surface in a very low shear region weakens field line bending stabilisation and amplifies the effects of toroidal coupling between modes, leading to the emergence of long-wavelength ideal or resistive infernal modes. These modes can grow collectively

EPFL2026

Turbulence-induced Safety Factor Profile Flattening at Rational Surfaces in Tokamaks with Low Magnetic Shear

Stephan Brunner

In this paper, we investigate the effects of ion-scale turbulence-generated currents on the local safety factor profile under conditions of low magnetic shear and proximity to rational surfaces, relevant to internal transport barrier formation. Our results show that turbulent currents can generate stationary zonal magnetic potential corrugations, producing a stepped safety factor profile with extended regions of zero magnetic shear. This change significantly affects turbulence self-interaction, resulting in

IOP Publishing Ltd2025

The Properties of Resistive Mhd Modes and Unstable Spectra in Advanced Tokamak Regimes

Advanced tokamak regimes, featuring extended regions of low magnetic shear, are promising candidates for future fusion reactors but are also more prone to specific kinds of MHD instabilities. The proximity to a rational surface in a very low shear region weakens field line bending stabilisation and amplifies the effects of toroidal coupling between modes, leading to the emergence of long-wavelength resistive infernal modes. These modes can grow collectively as a discrete spectrum, leading to a cascade of di

IOP Publishing Ltd2025

Axisymmetric oscillations at L-H transitions in JET: M-mode

Nicola Vianello, Antonio José Pereira de Figueiredo

L to H transition studies at JET have revealed an n = 0, m = 1 magnetic oscillation starting immediately at the L to H transition (called M-mode for brevity). While the magnetic oscillation is present a weak ELM-less H-mode regime is obtained, with a clear ...

IOP Publishing Ltd2017

Neoclassical tearing mode seeding by coupling with infernal modes in low-shear tokamaks

Jonathan Graves, Wilfred Anthony Cooper, Federico David Halpern, Daniele Brunetti, Andreas Kleiner

A numerical and an analytical study of the triggering of resistive MHD modes in tokamak plasmas with low magnetic shear core is presented. Flat q profiles give rise to fast growing pressure driven MHD modes, such as infernal modes. It has been shown that i ...

IOP Publishing Ltd2016

Guiding-centre transformation of the radiation-reaction force in a non-uniform magnetic field

Joan Decker

In this paper, we present the guiding-centre transformation of the radiation reaction force of a classical point charge travelling in a non-uniform magnetic field. The transformation is valid as long as the gyroradius of the charged particles is much small ...

Cambridge University Press2015

Extended MHD simulations of infernal mode dynamics and coupling to tearing modes

Jonathan Graves, Wilfred Anthony Cooper, Federico David Halpern, Daniele Brunetti

A numerical study of pressure driven magnetohydrodynamic (MHD) instabilities in a low-shear tight aspect ratio configuration is presented. When the magnetic shear is sufficiently small over an extended region in the core, enhanced instability occurs due to ...

Iop Publishing Ltd2015

Kinetic modelling of runaway electron avalanches in tokamak plasmas

Joan Decker

Runaway electrons can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force owing to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate runawa ...

Iop Publishing Ltd2015

ADX: a high field, high power density, advanced divertor and RF tokamak

Christian Gabriel Theiler, Francesca Maria Poli, Yu Lin

The MIT Plasma Science and Fusion Center and collaborators are proposing a high-performance Advanced Divertor and RF tokamak eXperiment (ADX)-a tokamak specifically designed to address critical gaps in the world fusion research programme on the pathway to ...

IOP Publishing Ltd2015

Three-dimensional distortions of the tokamak plasma boundary: boundary displacements in the presence of saturated MHD instabilities

Jonathan Graves, Wilfred Anthony Cooper, Daniele Brunetti

The three-dimensional plasma boundary displacement induced by long-lasting core magnetohydrodynamic (MHD) instabilities has been measured in JET, MAST and NSTX. Only saturated instabilities are considered here since transient rapidly growing modes which de ...

IOP Publishing Ltd2014

Analysis of global hydromagnetic instabilities driven by strongly sheared toroidal flows in tokamak plasmas

Jonathan Graves

Recent numerical calculations have shown that while strong toroidal rotation can increase the external kink limit of tokamak plasmas, the associated rotation shear can drive a Kelvin-Helmholtz like global instability in the plasma, if the rotation frequenc ...

Iop Publishing Ltd2013

Ideal ballooning modes in the tokamak scrape-off layer

Paolo Ricci, Joaquim Loizu Cisquella, Sébastien Jolliet, Federico David Halpern, Annamaria Mosetto

A drift-reduced Braginskii fluid model is used to carry out a linear and non-linear study of ideal ballooning modes in the tokamak scrape-off layer. First, it is shown that the scrape-off layer finite connection length and boundary conditions modify the id ...

American Institute of Physics2013

Global two-fluid simulations of tokamak Scape-Off-Layer turbulence

Sébastien Jolliet

We present non-linear self-consistent 3D global fluid simulations of the SOL plasma dynamics using the Global Braginskii Solver (GBS) code. The code solves the drift-reduced Braginkii equations in a collisional plasma, with cold ions. The GBS code, originally developed for an electrostatic, 2D configuration has been recently upgraded to describe the SOL turbulence with the introduction of the variable curvature along the magnetic field lines, the magnetic shear, and the electromagnetic effects. The code pec

2012

A comprehensive study of electrostatic turbulence and transport in the laboratory basic plasma physics device TORPEX

Ambrogio Fasoli, Ivo Furno

TORPEX is a toroidal device located at the CRPP-EPFL in Lausanne. In TORPEX, a vertical magnetic field superposed on a toroidal field creates helicoidal field lines with both ends terminating on the torus vessel. The turbulence driven by magnetic curvature and plasma gradients causes plasma transport in the radial direction while at the same time plasma is progressively lost along the field lines. The relatively simple magnetic geometry and diagnostic access of the TORPEX configuration facilitate the experi

2012

Global two-fluid simulations of tokamak SOL turbulence

We present non-linear self-consistent global simulations of the SOL plasma dynamics using the Global Braginskii Solver (GBS) code. The code solves on the drift-reduced Braginkii equations, with cold ions. Studied originally for the simulation of the Simple Magnetized Torus (SMT) experiment TORPEX (CRPP, Lausanne), the GBS code has been recently upgraded to describe the SOL turbulence with the introduction of the variable curvature along the magnetic field lines, the magnetic shear, and the electromagnetic e

2011

Basic Investigation of Turbulent Structures and Blobs of Relevance for Magnetic Fusion Plasmas

Christian Gabriel Theiler

Similarly to neutral fluids, plasmas often exhibit turbulent behavior. Turbulence in plasmas is usually more complex than in neutral fluids due to long range interactions via electric and magnetic fields, and kinetic effects. It gives rise to many interest ...

EPFL2011

Full tokamak discharge simulation and kinetic plasma profile control for ITER

Sun Hee Kim

Understanding non-linearly coupled physics between plasma transport and free-boundary equilibrium evolution is essential to operating future tokamak devices, such as ITER and DEMO, in the advanced tokamak operation regimes. To study the non-linearly couple ...

EPFL2009

Stability analysis of internal ideal modes in low-shear tokamaks

Jonathan Graves

The stability of internal, ideal modes in tokamaks with low magnetic shear in the plasma core is analyzed. For equilibria with large aspect ratio, a parabolic pressure profile and a flat q profile in the core, an exact solution of the ideal magnetohydrodyn ...

American Institute of Physics (AIP)2007

Rapid and localized electron internal-transport-barrier formation during shear inversion in fully noninductive TCV discharges

Olivier Sauter, Stefano Coda, Timothy Goodman, Antoine Pochelon, Mark Henderson, Petri Nikkola

Clear evidence is reported for the first time of a rapid localized reduction of core electron energy diffusivity during the formation of an electron internal-transport barrier. The transition occurs rapidly (similar or equal to3 ms), during a slow (similar or equal to200 ms) self-inductive evolution of the magnetic shear. This crucial observation, and the correlation of the transition with the time and location of the magnetic shear reversal, lend support to models attributing the reduced transport to the l

2004

Neoclassical tearing modes on ASDEX upgrade: improved scaling laws, high confinement at high, beta N and new stabilization experiments

Olivier Sauter

In this paper, recent results on the physics of neoclassical tearing modes (NTMs) achieved on ASDEX Upgrade are reported. A scaling law for NTM decay has been found, showing that the minimum local bootstrap current density required for mode growth is proportional to the ion gyro radius. As this scaling law does not depend on the seed island size, and thus on the background MHD activity, it is more reliable than previously derived scaling laws for the NTM onset. Furthermore, the recently reported frequently

IOP Publishing Ltd2003

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