Observations of zonal flows in electrode biasing experiments on the Joint Texas Experimental tokamak

Geodesic acoustic modes (GAMs) are ubiquitous oscillatory flow phenomena observed in toroidal magnetic confinement fusion plasmas, such as tokamaks and stellarators. They are recognized as the non-stationary branch of the turbulence driven zonal flows which play a critical regulatory role in cross-field turbulent transport. GAMs are supported by the plasma compressibility due to magnetic geodesic curvature—an intrinsic feature of any toroidal confinement device. GAMs impact the plasma confinement via velocity shearing of turbulent eddies, modulation of transport, and by providing additional routes for energy dissipation. GAMs can also be driven by energetic particles (so-called EGAMs) or even pumped by a variety of other mechanisms, both internal and external to the plasma, opening-up possibilities for plasma diagnosis and turbulence control. In recent years there have been major advances in all areas of GAM research: measurements, theory, and numerical simulations. This review assesses the status of these developments and the progress made towards a unified understanding of the GAM behaviour and its role in plasma confinement. The review begins with tutorial-like reviews of the basic concepts and theory, followed by a series of topic orientated sections covering different aspects of the GAM. The approach adopted here is to present and contrast experimental observations alongside the predictions from theory and numerical simulations. The review concludes with a comprehensive summary of the field, highlighting outstanding issues and prospects for future developments.

Section: Toroidal and Poloidal Mode Structuresupporting

confidence: 62%

Section: Plasma Biasingmentioning

confidence: 92%

Section: H-modementioning

confidence: 99%

See 1 more Smart Citation

Geodesic acoustic modes in magnetic confinement devices

Smolyakov

Ido

2021

“…There are empirical evidences of Zonal Flows triggering the L-H transition in Alcator C-mode [170] and in EAST [171,172] tokamaks. The presence of ZF during Limit Cycle Oscillations (LCO) is reported in tokamak plasmas at the L-H transition [173,174] and having shearing rates comparable to the mean shearing rate [175]. The interaction between × flows and turbulence has the form of predator-prey model in the proximity of the L-H transition, which is known as limit cycle oscillations (LCO).…”

mentioning

confidence: 99%

Frequency and plasma condition dependent spatial structure of low frequency global potential oscillations in the TJ-II stellarator

Kobayashi¹,

Losada²,

Liu³

et al. 2019

y a toda la gente que me apoyó: mis amigos Eric, Patricio, Antonio González y Carlos Raúl. También Marga, Teresita, Idelsa, Isabel, etc. Gracias a Karen Velázquez por haber sido una cercana compañía en mi vida y en los momentos finales de esta tesis. Especialmente gracias una persona que es como mi hermano de sangre, Juan Carlos Arias Valdes.Pero sobre todo, gracias á miña familia, meus pais, Ramón e Pura, o meu irmau Jorge, os meus avós Manolo, Celeste, Avelino e Pura. Os meus bisavós Eudosia e José. As miñas tías Avelina, Manuela, María, meu tío Pepe e meus primos Brais e María. Meus tíos Amaro e Carmen. Gardo un espacio privilexiado para os meus amigos de sempre de Cenlle: Dani e Diego, por quenes teño un profundo amor e respecto, xa que non tuveron as mesmas oportunidades que min nin unha vida tan sinxela. Gracias a todas esas persoas que conocín xogando ó fútbol en Galicia, especialmente a Manuel Iglesias (Fleitas), así como a Marcos, Borja, Miguel Freire, Fran, Hugo García, entre outros. Gracias a Carolina Méndez, por ser unha persoa tan importante para min e por apoiarme desde o principio, habendo estado ó meu lado durante os momentos críticos.Non podo esquecerme dos meus compañeiros da Universidade de Vigo, que me acompañaron durante a Licenciatura en Física, por 5 anos. Especial recordo teño para Javi, Hugo e Miguel. Imposible sería esquecer todo o tempo que pasamos xuntos estudanto Física e apoiándonos, que acabou resultando en sendos fermosos percorridos profesionais no ámbito da física. Esta tesis tamén vai adicada a eles, así como a os meus profesores durante o pre-universitario, Margarita Aller, Alberto Viso, Jorge Casalderrei e Aurelio.Tambem para as pessoas especiais que estão agora no belo país de São Tomé e Principe.Para todos eles e outros companheiros com quem naveguei pelos mares mais bravos e dos quais extraí as mais valiosas sabedorias, este trabalho é dedicado. Moito Obrigado.

“…, and the density radial gradient is obtained by ∇ r n 0 = n e,2 − n e,1 /Δ r . This method of measuring the electric field and turbulent transport, where the effect of electron temperature is neglected [5], has been proved to be feasible in HL-2A tokamak [10,29] and several other devices [12,30,31]. Local density and electric field measurements allow us to directly determine fluctuation-induced particle flux and these linear terms in the particle balance equation (1).…”

Section: Methodsmentioning

confidence: 99%

Fluctuation-induced inward particle flux during L–I–H transition on HL-2A tokamak

Lan

Ding

et al. 2021

The inward particle flux associated with the global long-lived mode (LLM) during the L–I–H transition on HL-2A tokamak has been measured. The inward particle flux arises from the phase change between density and radial velocity fluctuations, where density and velocity fluctuations are strongly correlated with magnetic fluctuations of LLM. Moreover, the radial velocity and its gradient rather than poloidal flow shear play an important role in particle transport associated with the large-scale mode. The strong nonlinear coupling between LLM and ambient turbulence has been confirmed, and this may contribute to most of the inward particle flux in the LLM during the I-phase state.