Toroidal Rotation in RF Heated JET Plasmas

Eriksson, L.‐G.; Hellsten, T.; Nave, M. F. F.; Brzozowski, J.; Holmström, Kerstin; Johnson, T.; Ongena, J.; Zastrow, K.‐D.

doi:10.1063/1.2800549

Cited by 4 publications

(8 citation statements)

References 28 publications

(57 reference statements)

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“…The role of spontaneous rotation on many tokamaks has been reported in several papers [23,24]. The magnitude of intrinsic or ICRF induced toroidal rotation has also been reported recently in JET Ohmic and in ICRF heated plasmas [25]. The paper shows that the magnitude of intrinsic rotation in JET Ohmic plasmas (LHCD only) is about 20 km s −1 in the plasma centre while the database of about 20 discharges with ICRF heating, v φ in the centre varies from −10 km s −1 to +20 km s −1 .…”

Section: Analysis Of Local Momentum and Ion Heat Diffusivities And Th...mentioning

confidence: 72%

Toroidal and poloidal momentum transport studies in JET

et al. 2007

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This paper reports on the recent studies of toroidal and poloidal momentum transport in JET. The ratio of the global energy confinement time to the momentum confinement is found to be close to τ E /τ φ =1 except for the low density discharges where the ratio is τ E /τ φ =2-3. On the other hand, local transport analysis of tens of discharges shows that the ratio of the local effective momentum diffusivity to the ion heat diffusivity is χ φ /χ i 0.1-0.4 rather than unity, as expected from the global confinement times and used in ITER predictions. The apparent discrepancy in the global and local momentum versus ion heat transport is explained by the fact that momentum confinement within edge pedestal is worse than that of the ion heat and thus, momentum pedestal is weaker than that of ion temperature. Another observation is that while the T i has a threshold in R/L Ti and profiles are stiff, the gradient in v φ increases with increasing torque and no threshold is found. Predictive transport simulations also confirm that χ φ /χ i 0.1-0.4 reproduce the core toroidal velocity profiles well. Concerning poloidal velocities on JET, the experimental measurements show that the carbon poloidal velocity can be an order of magnitude above the neo-classical estimate within the ITB. This significantly affects the calculated radial electric field and therefore, the E×B flow shear used for example in transport simulations. The Weiland model reproduces the onset, location and strength of the ITB well when the experimental poloidal rotation is used while it does not predict an ITB using the neo-classical poloidal velocity. The most plausible explanation for the generation of the anomalous poloidal velocity is the turbulence driven flow through the Reynold's stress. Both TRB and CUTIE turbulence codes show the existence of an anomalous poloidal velocity, being significantly larger than the neo-classical values. And similarly to experiments, the poloidal velocity profiles peak in the vicinity of the ITB and is caused by flow due to the Reynold's stress.

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Section: Analysis Of Local Momentum and Ion Heat Diffusivities And Th...mentioning

confidence: 72%

Toroidal and poloidal momentum transport studies in JET

et al. 2007

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“…To test the predictions for the size of the momentum flux arising from the inclusion of turbulent acceleration, we have implemented theu 1s terms given by (8) in the local, δf gyrokinetic code stella [45]. For the sake of simulation efficiency, we do not separately evolve g 1s,k and g 2s,k ; instead, we simulate a single equation for g s,k = g 1s,k + g 2s,k , (4) and (9):…”

Section: Simulation Equations and Resultsmentioning

confidence: 99%

“…As the plasma pressure in tokamaks is small compared to the magnetic pressure, |β | is typically small. The parallel acceleration given by (8) is then dominated by the turbulent contributions.…”

Section: Symmetry-breaking Induced By Turbulent Accelerationmentioning

confidence: 99%

“…Observational evidence obtained from a wide range of tokamaks indicates that axisymmetric plasmas exhibit differential toroidal rotation even in the absence of an externally applied torque (cf. [1,2,3,4,5,6,7,8,9,10,11]). This 'intrinsic rotation' is determined by momentum redistribution within the plasma, which is typically dominated by turbulent transport.…”

Section: Introductionmentioning

confidence: 99%

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Intrinsic rotation driven by turbulent acceleration

Barnes

Parra

2018

Plasma Phys. Control. Fusion

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Differential rotation is induced in tokamak plasmas when an underlying symmetry of the governing gyrokinetic-Maxwell system of equations is broken. One such symmetry-breaking mechanism is considered here: the turbulent acceleration of particles along the mean magnetic field. This effect, often referred to as the 'parallel nonlinearity', has been implemented in the δf gyrokinetic code stella and used to study the dependence of turbulent momentum transport on the plasma size and on the strength of the turbulence drive. For JET-like parameters with a wide range of driving temperature gradients, the momentum transport induced by the inclusion of turbulent acceleration is similar to or smaller than the ratio of the ion Larmor radius to the plasma minor radius. This low level of momentum transport is explained by demonstrating an additional symmetry that prohibits momentum transport when the turbulence is driven far above marginal stability.

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“…Plasma rotation without significant external momentum injection is in this context particularly interesting since, unlike in today's experiments, Neutral Beam Injection in ITER is not expected to give rise to significant rotation. Experiments [26] aimed at studying plasma rotation in ICRF heated plasmas with little or no external momentum input in both plasmas with ICRF and LH have been carried out. The rotation profiles have been measured by CXRS (Charge Exchange Recombination Spectroscopy), using short diagnostic NBI pulses.…”

Section: Rotation In Icrf Heated Plasmasmentioning

confidence: 99%

Overview of recent results on Heating and Current Drive in JET

Ongena¹,

Baranov²,

Bobkov

et al. 2007

AIP Conference Proceedings

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Recent progress on heating and current drive on JET is reported. Topics discussed are: high power coupling of ICRF/LH at ITER relevant antenna/launcher-separatrix distances, succesfull demonstration of 3dB couplers for ELM tolerance of the ICRF system, influence of ICRF on LH operation, rotation studies in plasma without external momentum with standard and enhanced JET toriodal field ripple, studies of different ICRF heating schemes and of NTM avoidance schemes using Ion Cyclotron Current Drive. A brief outlook on future plans for experiments at JET is given.

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Toroidal Rotation in RF Heated JET Plasmas

Cited by 4 publications

References 28 publications

Toroidal and poloidal momentum transport studies in JET

Toroidal and poloidal momentum transport studies in JET

Intrinsic rotation driven by turbulent acceleration

Overview of recent results on Heating and Current Drive in JET

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