Shape dependence of sawtooth inversion radii and profile peaking factors in TCV L mode plasmas

Plasma and Fusion Research

2013

Recent research on turbulent transport of particle and toroidal momentum in the core of tokamak plasmas is reviewed. Similarities and differences between these two transport channels are briefly presented, highlighting the common feature that both include large off-diagonal components in the radial flux. The main goal of the review is to provide selected recent examples of validation studies in these topical areas, and, thereby, to outline an efficient route to validation in the complex field of transport studies dedicated to transport channels which include important off-diagonal components.

Section: Considerations On the Validationsupporting

confidence: 71%

Particle and Momentum Transport in Tokamak Plasmas, the Complicated Path towards the Experimental Validation of the Theoretical Predictions of Transport in Fusion Plasmas

Plasma and Fusion Research

2013

“…The peaking of the density profiles in these plasmas is in contrast with the flattening that is often observed in plasmas with central electron heating [37,38,39,40]. However, a detailed analysis of the electron and boron particle transport at mid-radius in these plasmas show that the experimental behaviors are well described by the theoretical modeling [41].…”

Section: Plasma Response To Ecrh Powermentioning

confidence: 99%

Effect of electron cyclotron resonance heating (ECRH) on toroidal rotation in ASDEX Upgrade H-mode discharges

McDermott

Plasma Phys. Control. Fusion

Dux

et al. 2011

Self Cite

Abstract. Core toroidal rotation behavior and momentum transport have been examined in neutral beam injection (NBI) heated plasmas with and without electron cyclotron resonance heating (ECRH) in ASDEX Upgrade (AUG). The impurity ion temperature and rotation are measured by means of charge exchange recombination spectroscopy (CXRS) and the main ion rotation is calculated neo-classically based on the measured impurity ion temperature and rotation profiles. In purely NBI heated discharges the plasma spins up in the co-current direction and forms peaked rotation profiles. However, when ECRH power is added to these discharges the rotation decreases significantly leading to flat and occasionally slightly hollow profiles. The rotation at the edge of the plasma (ρ > 0.65) is largely unaffected by the application of the ECRH. During ECRH phases the electron temperature in the core increases dramatically concomitant with a flattening of the ion temperature profile. In these phases peaking of the impurity ion and electron density profiles is also observed. The change in toroidal rotation is sensitive to both the amount of ECRH power deposited as well as to the deposition location. The measured rotation changes can not be explained by a modification to the NBI torque deposition profile, a preferential loss of fast ions from the plasma core, or by a simple increase in momentum diffusivity. Additionally, the inward directed Coriolis momentum pinch is predicted to increase, not decrease, during the ECRH phases. Altogether, the data suggest the presence of either an outward convection of momentum or an intrinsic, counter-current directed torque. Although the physics behind these possibilities remains unclear, they are presumably related to either a convective or residual stress driven momentum flux, which responds to the ECRH-induced changes in the plasma profiles and turbulence.

“…In figure 7(a) we compile the stationary normalized density gradients versus −ω QL R , such that the transition from a TEM to an ITG dominated regime is read from left to right, for theν − scan (open symbols: pentagrams, hexagrams, squares, crosses). We also add points from two additional s −ν scans performed at R/L Te = [10,12], R/L Ti = [6,7] to put in evidence the dependencies in the TEM branch (smaller open symbols: left triangles, up triangles, stars).…”

Section: Addressing the Experimental Observationsmentioning

confidence: 99%

The role of ion and electron electrostatic turbulence in characterizing stationary particle transport in the core of tokamak plasmas

Fable¹,

Plasma Phys. Control. Fusion

Sauter

2009

Self Cite

108

173

Abstract. A general feature of particle transport in the core of Tokamak plasmas is that, when core particle sources are small, a stationary peaked density profile is provided by a balance of outward diffusion and inward convection, driven by either neoclassical or turbulent mechanisms. The turbulent contribution to the off-diagonal elements of the transport matrix is very sensitive on the type of dominant instability of the background turbulence. We present here a detailed quasilinear gyrokinetic analysis of stationary turbulent particle transport by means of analytical and numerical calculations to show how the actual parametric dependence of the stationary normalized density gradient can strongly vary between an Ion Temperature Gradient (ITG) dominated turbulence and a Trapped Electron Mode (TEM) dominated turbulence regime. It is also shown how the maximal achievable normalized density gradient is reached when the turbulence regime is in a mixed state. This result is interpreted as the interplay of different physical mechanisms arising from (linear) wave-particle resonances. The results presented here are addressed to interpret some of the still unresolved issue in interpreting known experimental results.