Scaling of rotation and momentum confinement in JET plasmas

Vries, P. C. de; Hua, M.-D.; McDonald, D. C.; Giroud, C.; Janvier, Miho; Johnson, M.F.; Tala, T.; Zastrow, K.‐D.; Contributors, Jet

doi:10.1088/0029-5515/48/6/065006

Cited by 59 publications

(88 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The central toroidal rotation velocity for ITER H-mode plasmas with NBI power of 34 MW, was predicted to be in the range of 10-170 km/s [4]. This is lower than currently observed at JET for the same Prandtl number (ratio between momentum and ion heat diffusivity) and with NBI power less than 20 MW [5]. It is important to note that ITER simulations depend on options of momentum transport whose theory is still evolving.…”

Section: -Introductionmentioning

confidence: 79%

See 1 more Smart Citation

JET intrinsic rotation studies in plasmas with a high normalized beta and varying toroidal field ripple

Nave

Eriksson

Giroud

et al. 2012

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

Understanding the origin of rotation in Ion Cyclotron Resonance Frequency (ICRF) heated plasmas is important for predictions for burning plasmas sustained by alpha particles, being characterized by a large population of fast ions and no external momentum input. The angular velocity of the plasma column has been measured in JET H-mode plasmas with pure ICRF heating for both the standard low toroidal magnetic ripple configuration, of about ~ 0.08% and, for increased ripple values up to 1.5 % [1]. These new JET rotation data were compared with the multi-machine scaling of ref. [2] for the Alfven-Mach number and with the scaling for the velocity change from L-mode into H-mode. The JET data do not fit well any of these scalings that were derived for plasmas that are co-rotating with respect to the plasma-current.With the standard low ripple configuration, JET plasmas with large ICRF heating power and normalized beta, βN ≈1.3, have a very small co-current rotation, with Alfven-Mach numbers significantly below those given by the rotation scaling of ref. [2]. In some cases the plasmas are actually counter-rotating. No significant difference between the H-mode and L-mode rotation is observed. Typically the H-mode velocities near the edge are lower than in Lmodes. With ripple values larger than the standard JET value, between 1% and 1.5%, H-mode plasmas were obtained where both the edge and the core counter rotated. I -IntroductionIntrinsic rotation can play a key role in the performance of future tokamak power plants where the momentum input will be small [3]. In present day tokamak experiments, rotation is mostly driven by the torque coming from the neutral beam injection (NBI). However, in reactors with high NBI power at high beam energy, the torque is expected to be small. The central toroidal rotation velocity for ITER H-mode plasmas with NBI power of 34 MW, was predicted to be in the range of 10-170 km/s [4]. This is lower than currently observed at JET for the same Prandtl number (ratio between momentum and ion heat diffusivity) and with NBI power less than 20 MW [5]. It is important to note that ITER simulations depend on options of momentum transport whose theory is still evolving. For instance, the ITER simulations of ref.[4] do not include any contribution from a momentum pinch which is found to exist in JET NBI discharges [6,7] and other tokamaks [8,9]. This inward pinch will modify the rotation profile in ITER, in particular the peaking of the rotation profile will increase. Understanding of momentum transport is crucial in order to reliably model rotation profiles in ITER and other future devices, however, this is not the scope of this paper. A good overview of momentum transport theory, covering also aspects like residual stress and up-down asymmetry that may affect significantly the rotation profile in ITER, is given in reference [10].As the NBI driven rotation in future machines is presumed to be small, the intrinsic plasma rotation, which occurs in the absence of momentum sources such as NBI, has...

show abstract

Section: -Introductionmentioning

confidence: 79%

“…2) than in the newer ELMy pulses (figs. [3][4][5], that may lead to a higher pedestal and core rotation.…”

Section: -Discussion and Conclusionmentioning

confidence: 99%

JET intrinsic rotation studies in plasmas with a high normalized beta and varying toroidal field ripple

Nave

Eriksson

Giroud

et al. 2012

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…Another experimental observation that guided this search for a dimensionless scaling is the correlation of the intrinsic toroidal velocity with the local T i [10,19] or the gradient in T i [33]. This correlation also holds in conditions with significant NBI-torque drive [34,35].…”

Section: Background: Empirical and Dimensionless Scaling Of Intrmentioning

confidence: 99%

Dimensionless size scaling of intrinsic rotation in DIII-D

et al. 2016

View full text Add to dashboard Cite

A dimensionless empirical scaling for intrinsic toroidal rotation is given; M A~βN ρ *, where M A is the toroidal velocity divided by the Alfvén velocity, β N the usual normalized β value, and ρ* is the ion gyroradius divided by the minor radius. This scaling describes well experimental data from DIII-D, and also some published data from C-Mod and JET.The velocity used in this scaling is in an outer location in minor radius, outside of the interior core and inside of the large gradient edge region in H-mode conditions. This scaling establishes the basic magnitude of the intrinsic toroidal rotation and its relation to the rich variety of rotation profiles that can be realized for intrinsic conditions is discussed. This scaling has some similarities to existing dimensioned scalings, both the (2012)]. These relationships are described.

show abstract

“…On the experimental side, a significant improvement in the characterization of the steady-state behaviour of toroidal rotation has been achieved, both in plasmas with external torque source [11][12][13][14] and in plasmas without external torque sources [15][16], which still exhibit non-zero toroidal rotation, the so-called "intrinsic rotation", whose physical origin is still under investigation. A rather surprising recent observation from steady-state momentum studies is that the effective momentum diffusivity is much lower than the ion heat diffusivity (P r eff = χ φ eff / χ i eff~0 .4 using the definition of χ φ as in Eq.1) [11,[13][14], apparently contradicting the theoretical expectations.…”

Section: Introductionmentioning

confidence: 99%

“…A rather surprising recent observation from steady-state momentum studies is that the effective momentum diffusivity is much lower than the ion heat diffusivity (P r eff = χ φ eff / χ i eff~0 .4 using the definition of χ φ as in Eq.1) [11,[13][14], apparently contradicting the theoretical expectations. It is clear that the existence of a momentum inward pinch would solve the apparent contradiction, allowing for similar diagonal diffusivities at the same time as different effective values.…”

Section: Introductionmentioning

confidence: 99%

Perturbative studies of toroidal momentum transport using neutral beam injection modulation in the Joint European Torus: Experimental results, analysis methodology, and first principles modeling

Mantica

Tala²,

Ferreira³

et al. 2010

Physics of Plasmas

Self Cite

View full text Add to dashboard Cite

ABSTRACT.Perturbative experiments have been carried out in the JET tokamak in order to identify the diffusive and convective components of toroidal momentum transport. The torque source was modulated either by modulating tangential neutral beam power or by modulating in anti-phase tangential and normal beams to produce a torque perturbation in the absence of a power perturbation. The resulting periodic perturbation in the toroidal rotation velocity was modelled using time dependent transport simulations in order to extract empirical profiles of momentum diffusivity and pinch. Details of the experimental technique, data analysis and modelling are provided. The momentum diffusivity in the core region (0.2<ρ<0.8) was found to be close to the ion heat diffusivity ( χ φ / χ i~0 .7-1.7) and a significant inward momentum convection term, up to 20m/s, was found, leading to an effective momentum diffusivity significantly lower than the ion heat diffusivity (

show abstract

Scaling of rotation and momentum confinement in JET plasmas

Cited by 59 publications

References 31 publications

JET intrinsic rotation studies in plasmas with a high normalized beta and varying toroidal field ripple

JET intrinsic rotation studies in plasmas with a high normalized beta and varying toroidal field ripple

Dimensionless size scaling of intrinsic rotation in DIII-D

Perturbative studies of toroidal momentum transport using neutral beam injection modulation in the Joint European Torus: Experimental results, analysis methodology, and first principles modeling

Contact Info

Product

Resources

About