Characterization of the angular momentum transport in ASDEX

Kallenbach, A.; Mayer, H. M.; Fußmann, G.; Mertens, V.; Stroth, U.; Vollmer, O.; Team, Asdex

doi:10.1088/0741-3335/33/6/004

Cited by 59 publications

(58 citation statements)

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“…Despite this difficulty, it was determined that the data sets with low levels of ECRH power or high levels of onaxis beam heating, which have the strongest central torque deposition, can be explained fully by reasonable increases in diffusivity with effective Prandtl numbers (Pr =χ ef f /χ i ) of order 0.5-1. This is consistent with many previous experimental results, which have shown that the ion heat and momentum transport channels are linked [46,47,18,48,52]. Examples of these two conditions can be seen in the first and third ECRH phases shown in Fig.…”

Section: Discussionsupporting

confidence: 92%

“…The total convective velocity can be calculated by using TRANSP computed torque density profiles and assuming that χ φ χ i [46,47,18,48,52]. It only makes sense to perform this calculation for cases where the profiles can not be explained by a reasonable increase in χ φ and at radii where a change in the toroidal rotation is actually observed.…”

Section: Calculation Of Required Torque or Outward Pinchmentioning

confidence: 99%

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

McDermott

Angioni

Dux

et al. 2011

Plasma Phys. Control. Fusion

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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.

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Section: Discussionsupporting

confidence: 92%

Section: Calculation Of Required Torque or Outward Pinchmentioning

confidence: 99%

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

McDermott

Angioni

Dux

et al. 2011

Plasma Phys. Control. Fusion

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“…Toroidal impurity rotation in ohmic plasmas (no net momentum input) is consistent with neoclassical predictions [24,33,34]; in ohmic L-mode discharges, impurities rotate in the direction opposite to the plasma current, so in general the assumption that the majority ions and impurities (which are most often measured) rotate in the same way might be questionable [34]. In neutral beam heated plasmas, which have substantial direct momentum input, the toroidal momentum confinement time is much shorter than the neoclassical predictions [8][9][10][11]. Toroidal rotation profiles have been used to infer E, [8,11].…”

Section: Introductionsupporting

confidence: 67%

Observations of central toroidal rotation in ICRF heated Alcator C-Mod plasmas

et al. 1998

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IntroductionRotation plays an important role in the transition from L-to H-mode [1][2][3][4].Poloidal rotation in the edge plasma region has been closely associated with the L-H transition [5-7], and toroidal momentum confinement is well correlated with energy confinement [8-11]. While there have been several diagnostic systems designed to measure impurity toroidal rotation in tokamak plasmas [8-33], most of the observations have been made in plasmas with an external momentum source, usually provided by neutral beams. Toroidal impurity rotation in ohmic plasmas (no net momentum input) is consistent with neoclassical predictions [24,33,34]; in ohmic L-mode discharges, impurities rotate in the direction opposite to the plasma current, so in general the assumption that the majority ions and impurities (which are most often measured) rotate in the same way might be questionable [34]. In neutral beam heated plasmas, which have substantial direct momentum input, the toroidal momentum confinement time is much shorter than the neoclassical predic- Experiment DescriptionThe observations presented here were obtained from the Alcator C- Mod [35] tokamak, a compact (major radius R = 67 cm, typical minor radius of 22 cm, and Observations of Toroidal Rotation and ScalingsShown in Fig clockwise, and the solid spectrum is blue-shifted, the argon is rotating clockwise, in same direction as the plasma current during the RF pulse. This is in the direction opposite to the rotation of impurities in ohmic L-mode plasmas [8,24,33,34]. The magnitude of the shift is -. 5 mA, which yields a toroidal rotation velocity of (.5 mA/3731.1 mA) x c = 4.0 x 106 cm/s, in the co-current direction. Since the major radius of Alcator C-Mod is 67 cm, this corresponds to an angular rotation speed of 60 kRad/sec.The toroidal rotation may also be determined from the heliumlike argon forbid-4 den line. Shown in Fig.3a and 3b are spectra recorded from a spectrometer viewing the plasma mid-plane, at an angle of 60 from a major radius, in a slight counter clockwise view. The spectra of Fig.3a were obtained from a 1.1 MA discharge (clockwise current), and there is a blue-shift of .13±.01 ml during the H-mode phase (solid spectrum), when the plasma stored energy increased by .12 MJ. This corresponds to a toroidal rotation velocity increase of (.13 mA/3994.3 mX)/sin(6*)x c = 1.0 x 107 cm/s (150 kRad/sec), in the co-current direction. The spectra of Fig.3b were obtained with the same view from a 1.0 MA discharge with the plasma current in the counter clockwise direction, and there is a red-shift of .07t.01 mA during the 2.7 MW ICRF pulse, indicating that the argon is rotating in the counter clockwise direction, again co-current. This L-mode discharge had a stored energy increase of 45 kJ, when the magnitude of the toroidal rotation velocity increased by 5.3 x 106 cm/s, and still opposite to the rotation direction in ohmic discharges.The phasing of the RF antennas for this case was the same as in Fig.3a. Shown in Fig.3c are spectra recorded from a 6* clockwise ...

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“…The toroidal momentum diffusivity is added to an ad hoc enhancement, taken in this case to be twice the neoclassical ion thermal diffusivity [27]. In the ASTRA calculations the toroidal velocity is assumed as v tor = 2.5×10 4 × T i (keV) assuming χ mom is proportional to χ i [32]. ICRF deposition profiles are taken from TORIC4 results provided by the TSC/TRANSP simulations.…”

Section: Iter Hybrid Scenariosmentioning

confidence: 99%

Simulation of the hybrid and steady state advanced operating modes in ITER

et al. 2007

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Abstract. Integrated simulations are done to establish a physics basis, in conjunction with present tokamak experiments, for the operating modes in ITER. Simulations of the hybrid mode are done using both fixed and free-boundary 1.5D transport evolution codes including CRONOS, ONETWO, TSC/TRANSP, TOPICS, and ASTRA. The hybrid operating mode is simulated using the GLF23 energy transport model. The injected powers are limited to the negative ion neutral beam (NBI), ion cyclotron (ICRF), and electron cyclotron (EC). Several plasma parameters and source parameters are specified for the hybrid cases to provide a comparison among the simulations. Simulations of the steady state operating mode are done with the same 1.5D transport evolution codes cited above. In these cases the energy transport model is more difficult to prescribe, so that energy confinement models will range from theory based to empirically based. The injected powers include the same sources for the hybrid with the possible addition of lower hybrid (LH). These simulations will be presented and compared with particular focus on code to code results when using the same energy transport model, and within the same code when using different energy transport models

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Characterization of the angular momentum transport in ASDEX

Cited by 59 publications

References 0 publications

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

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

Observations of central toroidal rotation in ICRF heated Alcator C-Mod plasmas

Simulation of the hybrid and steady state advanced operating modes in ITER

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