Microinstability theory in tokamaks

Tang, W. M.

doi:10.1088/0029-5515/18/8/006

Cited by 345 publications

(234 citation statements)

References 207 publications

(617 reference statements)

Supporting

Mentioning

227

Contrasting

Unclassified

Order By: Relevance

“…It can be regarded as one of the most intriguing results of half a century in physics of hot magnetized plasmas, that in macroscopically stable equilibria the confinement is nevertheless determined by micro-scale instabilities and fluctuations, with transport of energy and particles across magnetic flux surfaces being dominated by ubiquitous turbulence on small (gyro radius) scales and low (drift) frequencies [1,2,3,4,5,6,7]. This turbulence is regulated by the formation of mesoscopic zonal structures out of the turbulent flows [8,9,10,11,12,13].…”

Section: Introductionmentioning

confidence: 99%

Flux-surface shaping effects on tokamak edge turbulence and flows

Kendl

Scott

2006

Physics of Plasmas

View full text Add to dashboard Cite

Shaping of magnetic flux surfaces is found to have a strong impact on turbulence and transport in tokamak edge plasmas. A series of axisymmetric equilibria with varying elongation and triangularity, and a divertor configuration are implemented into a computational gyrofluid turbulence model. The mechanisms of shaping effects on turbulence and flows are identified. Transport is mainly reduced by local magnetic shearing and an enhancement of zonal shear flows induced by elongation and X-point shaping.

show abstract

Section: Introductionmentioning

confidence: 99%

Flux-surface shaping effects on tokamak edge turbulence and flows

Kendl

Scott

2006

Physics of Plasmas

View full text Add to dashboard Cite

show abstract

“…The observation of two distinct turbulent states casts illumination on the understanding of turbulent transport. Many kinds of instabilities in the range of the drift wave frequency have been studied in toroidal plasmas [24]. Recently it has been pointed out that competition among different instabilities affects the saturation of turbulence [25,26].…”

mentioning

confidence: 99%

Slow Transition of Energy Transport in High-Temperature Plasmas

et al. 2006

View full text Add to dashboard Cite

A new slow transition process for energy transport in magnetically confined plasmas is reported. The slow transition is characterized by the change between two metastable transport conditions characterized by a weak and a strong electron temperature (T e ) dependence of normalized heat flux. These two branches are found to merge at the critical T e gradient. In metastable transport, the derivative of normalized heat flux to the T e gradient, @ Q e =n e =@ ÿrT e , is positive, while it becomes negative during the transition phase. The time for the transition increases as the normalized T e gradient is increased and exceeds the transport time scale characterized by the global energy confinement time. High-temperature plasmas, which are seen in nature or confined in laboratory experimental devices, are very often far from equilibrium. One of the noticeable features is that the observed temperature profiles are realized as a balance between the flux of energy and turbulence-driven transport. A sudden and distinctive jump in the profiles has been found, e.g., the H-mode phenomena in tokamak plasmas [1]. The concept of a profile transition has been employed in order to understand the formation and dynamics of a self-sustained radial profile in inhomogeneous plasmas [2]. The transitions in the profiles in H-mode plasmas are caused by the S-curve property (cusp-type catastrophe) in the gradient-flux relation, showing a feature analogous to the first-order phase transition [3,4]. As the second-order phase transition exists in terrestrial matter, it is possible that the other type of transition exists in the process of transport barrier formation in plasmas [4]. We here report the discovery of a new, slowly evolving transition between two transport branches that have different electron temperature (T e ) dependences, in toroidal plasmas.Heat transport in a magnetically confined toroidal plasma is strongly governed by turbulence. The mechanism of the H-mode transition has been studied both experimentally [5,6] and theoretically [7][8][9][10]. The bifurcation of the radial electric field and the associated suppression of turbulence are the key parameters to explain the fast transition between L mode and H mode [2,[7][8][9]. This transition mechanism appears as various phenomena such as the electric pulsation observed in the toroidal helical plasma and the internal transport barrier [11]. In parallel with these rapidly evolving phenomena, slow evolutions into the state of improved plasma confinement have also been observed in a slowly developing edge transport barrier [12] and in other confinement improved modes. Improved Ohmic confinement mode [13], counter-neutral beam injection improved mode [14], pellet enhanced performance mode [15], radiatively improved mode [16] associated with the change of density profiles without a clear fast transition. Although these improved modes associated with the slow transition are as important as the improved mode with a fast transition, the mechanism of the slow transition has been studie...

show abstract

“…The discrepancy is attributed to small scale plasma turbulence [14]. It is well known that small scale instabilities can cause enhanced transport in plasmas and they are major contenders to explain this difference.…”

Section: Magnetic Curvaturementioning

confidence: 99%

“…Using equations (23,24,25), the position vector r = x x + y y + z z is known everywhere on the magnetic surface. Then one can evaluate all the quantities required in equations (17,14,19) by calculating the following quantities (in that order)…”

Section: Visualizationmentioning

confidence: 99%

Visualization of magnetically confined plasmas

Lewandowski

1999

Computing and Visualization in Science

View full text Add to dashboard Cite

With the rapid developments in experimental and theoretical fusion energy research towards more geometric details, visualization plays an increasingly important role. In this paper we will give an overview of how visualization can be used to compare and contrast some different configurations for future fusion reactors. Specifically we will focus on the stellarator and tokamak concepts. In order to gain understanding of the underlying fundamental differences and similarities these two competing concepts are compared and contrasted by visualizing some key attributes.

show abstract

Microinstability theory in tokamaks

Cited by 345 publications

References 207 publications

Flux-surface shaping effects on tokamak edge turbulence and flows

Flux-surface shaping effects on tokamak edge turbulence and flows

Slow Transition of Energy Transport in High-Temperature Plasmas

Visualization of magnetically confined plasmas

Contact Info

Product

Resources

About