An edge-localized mode (ELM) is a plasma instability occurring in the edge region of a tokamak plasma due to periodic relaxations of the edge transport barrier in high-confinement mode. Each ELM burst is associated with expulsion of particles and energy from the confined plasma into the scrape-off layer. This phenomenon was first observed in the ASDEX tokamak in 1981. Diamagnetic effects in the model equations expand the size of the parameter space in which solutions of repeated sawteeth can be recovered compared to a resistive MHD model. An ELM can expel up to 20 percent of the reactor's energy.
ELM is a major challenge in magnetic fusion research with tokamaks, as these instabilities can:
Damage wall components (in particular divertor plates) by ablating them away due to their extremely high energy transfer rate (GW/m2);
Potentially couple or trigger other instabilities, such as the resistive wall mode (RWM) or the neoclassical tearing mode (NTM).
A variety of experiments/simulations have attempted to mitigate damage from ELM. Techniques include:
Application of resonant magnetic perturbations (RMPs) with in-vessel current carrying coils can eliminate or weaken ELMs.
Injecting pellets to increase the frequency and thereby decrease the severity of ELM bursts (ASDEX Upgrade).
Multiple small-scale ELMs (000s/s) in tokamaks to prevent the creation of large ones, spreading the associated heat over a larger area and interval
Increase the plasma density and, at high densities, adjusting the topology of the magnetic field lines confining the plasma.
In 2003 DIII-D begn experimenting with resonant magnetic perturbations to control ELMs.
In 2006 an initiative (Project Aster) was started to simulate a full ELM cycle including its onset, the highly non-linear phase, and its decay. However, this did not constitute a “true” ELM cycle, since a true ELM cycle would require modeling the slow growth after the crash, in order to produce a second ELM.
As of late 2011, several research facilities had demonstrated active control or suppression of ELMs in tokamak plasmas.
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thumb|Vue intérieure du tore du Tokamak à configuration variable (TCV), dont les parois sont recouvertes de tuiles de graphite. Un tokamak est un dispositif de confinement magnétique expérimental explorant la physique des plasmas et les possibilités de produire de l'énergie par fusion nucléaire. Il existe deux types de tokamaks aux caractéristiques sensiblement différentes, les tokamaks traditionnels toriques (objet de cet article) et les tokamaks sphériques.
An edge-localized mode (ELM) is a plasma instability occurring in the edge region of a tokamak plasma due to periodic relaxations of the edge transport barrier in high-confinement mode. Each ELM burst is associated with expulsion of particles and energy from the confined plasma into the scrape-off layer. This phenomenon was first observed in the ASDEX tokamak in 1981. Diamagnetic effects in the model equations expand the size of the parameter space in which solutions of repeated sawteeth can be recovered compared to a resistive MHD model.
The first MOOC to teach the basics of plasma physics and its main applications: fusion energy, astrophysical and space plasmas, societal and industrial applications
Learn the basics of plasma, one of the fundamental states of matter, and the different types of models used to describe it, including fluid and kinetic.
Learn the basics of plasma, one of the fundamental states of matter, and the different types of models used to describe it, including fluid and kinetic.
Explore les caractéristiques du plasma brûlant, le rôle des ions rapides, les pertes, les modes MHD, la turbulence, l'interaction des ondes d'Alfvén et la stabilité des brûlures.
Explore la physique au bord des dispositifs de fusion, en mettant l'accent sur le confinement du plasma et l'optimisation du fonctionnement du réacteur de fusion.
Explore les progrès de la fusion par confinement magnétique, les feuilles de route vers la puissance de fusion, les composants ITER et le chemin vers DEMO.
This thesis focuses on the physics of suprathermal electrons generated by electron cyclotron (EC) waves in tokamak plasmas, which play an important role in the physics of current drive and energetic p
Edge Localised Mode (ELM)-induced heat loads, in particular divertor heat loads present one of the main challenges in adopting nuclear fusion as an industrial-scale energy source. At present, the type
Neoclassical tearing modes (NTM) must be controlled or suppressed to prevent a degradation of the energy confinement in tokamak plasmas. This can be done applying RF-current via electron cyclotron cur