Overview of toroidal momentum transport

Peeters, A. G.; Angioni, C.; Bortolon, A.; Camenen, Y.; Casson, F. J.; Duval, B. P.; Fiederspiel, L.; Hornsby, W. A.; Idomura, Yasuhiro; Hein, T.; Kluy, N.; Mantica, P.; Parra, Félix I.; Snodin, A. P.; Szepesi, G.; Strintzi, D.; Tala, T.; Tardini, G.; Vries, P. C. de; Weiland, Jan

doi:10.1088/0029-5515/51/9/094027

Cited by 132 publications

(222 citation statements)

References 121 publications

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“…whereṽ r E is the radial component of the perturbed E × B velocity,f is the perturbed velocity distribution, m is the ion mass, v is the velocity parallel to the magnetic field, and s is the field aligned coordinate, see for example [25]. Hence, this equation represents the radial transport of parallel velocity perturbations via the radial component of the fluctuating E × B drift.…”

Section: Iii1 Discussion Of Physics Behind Intrinsic Rotation Revermentioning

confidence: 99%

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

McDermott¹,

Angioni²,

Conway³

et al. 2014

Nucl. Fusion

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Abstract. The ASDEX Upgrade intrinsic rotation database has been expanded to include a large number of measurements from Ohmic L-mode discharges covering a wide range of plasma densities, currents, and magnetic fields. This database was then used to study the rotation behavior across the transition from linear to saturated Ohmic confinement (LOC/SOC). At low collisionailty the plasma is in the LOC regime and the toroidal rotation profile is in the co-current direction. As the collisionality is increased and the plasma transitions from LOC to SOC, the core rotation decreases resulting in a hollow, counter-current profile. Even deeper in the SOC regime, however, a second reversal back toward the co-current direction occurs. Linear gyrokinetic calculations indicate that these reversals can not be explained by a transition from a trapped electron mode (TEM) to an ion temperature gradient (ITG) dominated regime. Rather, the analysis indicates that the intrinsic normalised rotation gradient, u', depends strongly on local plasma parameters, in particular on R/L ne . Taken together with turbulent particle transport theory, these results suggest that the coto counter-current directed rotation reversal occurs in the TEM regime due to profile changes and not due to transition from TEM to ITG. The second reversal back to the co-current direction is explained by the reduction of R/L ne observed in ITG dominated plasmas. Lastly, a simple linear model for the residual stress assuming a fixed poloidal tilt angle of the turbulent eddies was applied to the database. This model is able to capture the main parameter dependencies observed in the data and demonstrates that at least two processes contributing to the poloidal tilt of the turbulent eddies are needed to reproduce the experimentally observed u' values: one proportional to the sign of the turbulence propagation and the second independent of ω r .

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Section: Iii1 Discussion Of Physics Behind Intrinsic Rotation Revermentioning

confidence: 99%

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

McDermott¹,

Angioni²,

Conway³

et al. 2014

Nucl. Fusion

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Section: -Introductionmentioning

confidence: 99%

“…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 created a lot of interest. The question of whether intrinsic rotation would on its own or as a supplement to NBI induced rotation be sufficient to fulfill the requirements for high confinement plasmas such as the suppression of turbulence and stabilization of MHD modes is a key issue.…”

mentioning

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

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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...

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“…Here χ ζ is the anomalous viscosity, V pinch is the pinch [31,32,33], Π res rζ is the residual stress [7,8,9], and a is a parallel acceleration [7,34] which acts as a local source. Π res rζ and a are required to spin-up plasmas from rest [8,9].…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Conversion of poloidal flows into toroidal flows by phase space structures in trapped ion resonance driven turbulence

Kosuga

Itoh

Diamond

et al. 2013

Plasma Phys. Control. Fusion

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A theory to describe the conversion of poloidal momentum into toroidal momentum by phase space structures in trapped ion resonance driven turbulence is presented. In trapped ion resonance driven turbulence, phase space structures are expected to form and can contribute to transport by exerting dynamical friction. Toroidal momentum flux by dynamical friction is calculated. It is shown that dynamical friction exerted on trapped ion granulations can mediate momentum transfer between poloidal and toroidal flows. The conversion coefficient is calculated as measurable, which can be validated in current devices.

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Overview of toroidal momentum transport

Cited by 132 publications

References 121 publications

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

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

Conversion of poloidal flows into toroidal flows by phase space structures in trapped ion resonance driven turbulence

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