X-ray observations of central toroidal rotation in ohmic Alcator C-Mod plasmas

Rice, J. E.; Marmar, E.; Bombarda, F.; Qu, Laiye

doi:10.1088/0029-5515/37/3/i11

Cited by 73 publications

(62 citation statements)

References 30 publications

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“…The Alcator C-Mod rotation results are summarized in the following. Lower single null Ohmic L-mode discharges are found to have a slight (∼10 km/s) counter-current rotation [26], and the magnitude and direction are consistent with neo-classical theory [27]. ICRF and Ohmic H-mode plasmas exhibit co-current rotation up to 100 km/s, without direct momentum input.…”

Section: Introductionsupporting

confidence: 61%

“…The C-Mod rotation observations in Ohmic L-mode plasmas [26] have previously been compared to the predictions of neo-classical theory [27]. The calculated magnitude, direction (counter-current) and independence on the mass of the impurity ions were found to be in agreement with the experiment for discharges with a lower single null.…”

Section: Comparisons With Theorymentioning

confidence: 72%

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Toroidal rotation and momentum transport in Alcator C-Mod plasmas with no momentum input

et al. 2004

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Section: Introductionsupporting

confidence: 61%

Section: Comparisons With Theorymentioning

confidence: 72%

Toroidal rotation and momentum transport in Alcator C-Mod plasmas with no momentum input

et al. 2004

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“…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 -.…”

Section: Observations Of Toroidal Rotation and Scalingsmentioning

confidence: 86%

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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“…204,205 Strong co-current rotation, with toroidal velocities up to 130 km/s (about 0.3 times the sound speed), has been observed and is strongest in enhanced confinement plasmas, i.e., the H-and I-mode. Under otherwise similar condition, the rotation state is independent of whether the plasma is heated with ICRF power or Ohmically, suggesting that the underlying mechanism is independent of the specific heating method.…”

Section: B Momentum Transport and Intrinsic Rotationmentioning

confidence: 99%

20 years of research on the Alcator C-Mod tokamak

et al. 2014

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The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only highpower radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing componentsapproaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated a) Paper AR1 1, Bull. Am. Phys. Soc. 58, 21 (2013). b) Invited speaker.

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X-ray observations of central toroidal rotation in ohmic Alcator C-Mod plasmas

Cited by 73 publications

References 30 publications

Toroidal rotation and momentum transport in Alcator C-Mod plasmas with no momentum input

Toroidal rotation and momentum transport in Alcator C-Mod plasmas with no momentum input

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

20 years of research on the Alcator C-Mod tokamak

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