Advances in lower hybrid current drive technology on Alcator C-Mod

Wallace, G.; Shiraiwa, S.; Hillairet, J.; Preynas, M.; Beck, W.; Casey, J.A.; Doody, J.; Faust, I.; Fitzgerald, E.; Johnson, D.; Kanojia, A.; Koert, P.; Lau, C.; Lin, Y.; Leccacorvi, R.; MacGibbon, P.; Meneghini, O.; Murray, Richard A.; Parker, R.; Terry, D.R.; Vieira, R.; Wilson, J. R.; Wukitch, S.J.; Zhou, Longfei

doi:10.1088/0029-5515/53/7/073012

Cited by 15 publications

(15 citation statements)

References 20 publications

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“…The discovery of ion cyclotron PDI in Alcator C-Mod was reported in the last IAEA meeting and the downshift of the sideband frequencies was found to be characteristic of the magnetic field strength near the inner separatrix [60,61]. The location of the PDI at onset has since been observed to be dependent on the X-point location [62].…”

Section: Parametric Decay and The Density Limit For Lhcdmentioning

confidence: 98%

Alcator C-Mod: research in support of ITER and steps beyond

et al. 2015

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Abstract. This paper presents an overview of recent highlights from research on Alcator C-Mod. Significant progress has been made across all research areas over the last two years, with particular emphasis on divertor physics and power handling, plasma-material-interaction studies, ELM-suppressed pedestal dynamics, core transport and turbulence, and RF heating and current drive utilizing Ion Cyclotron and Lower Hybrid tools. Specific results of particular relevance to ITER include: inner wall SOL transport studies that have led, together with results from other experiments, to the change of the detailed shape of the inner wall in ITER; runaway electron studies showing that the critical electric field required for runaway generation is much higher than predicted from collisional theory; core tungsten impurity transport studies reveal that tungsten accumulation is naturally avoided in typical C-Mod conditions.

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Section: Parametric Decay and The Density Limit For Lhcdmentioning

confidence: 98%

Alcator C-Mod: research in support of ITER and steps beyond

et al. 2015

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“…This launcher will be located off the midplane where improved single pass absorption can be achieved. 357,368 The design reduces reflected power via a toroidal bi-junction while retaining the control of the n k spectrum. Velocity space synergy with the midplane launcher is predicted to maximize the driven current at ITER relevant densities.…”

Section: B Decrease Of Lhcd Efficiency At High Densitymentioning

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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“…These parameters are favourable for toroidal electric current driven by LH waves, where the rf-driven current is generated efficiently in the co-current direction [32]. Recent results from C-Mod LHCD experiments may be found in [33][34][35][36][37]. H-mode is accessed with up to 5 MW of ICRF power, usually by H minority heating in D plasmas [31] at 5.4 T.…”

Section: Introductionmentioning

confidence: 99%

Effects of LHRF on toroidal rotation in Alcator C-Mod plasmas

Rice¹,

Podpaly²,

Reinke³

et al. 2013

Nucl. Fusion

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Application of lower hybrid range of frequencies (LHRF) waves can induce both co-and counter-current directed changes in toroidal rotation in Alcator C-Mod plasmas, depending on the target plasma current, electron density, confinement regime and magnetic shear. For ohmic L-mode discharges with good core LH wave absorption, and significant current drive at a fixed LH power near 0.8 MW, the interior (r/a < 0.5) rotation increments (on a time scale of order the current relaxation time) in the counter-current direction if n e (10 20 m −3) > q 95 /11.5, and in the co-current direction if n e (10 20 m −3) < q 95 /11.5. All discharges with co-current rotation changes have q 0 > 1, indicating a good correlation with driven current fraction, unifying the results observed on various tokamaks. For high density (n e 1.2 × 10 20 m −3) L-mode target discharges, where core LH wave absorption is low, the rotation change is in the co-current direction, but evolves on a shorter momentum transport time scale, and is seen across the entire spatial profile. For H-mode target plasmas, both co-and counter-current direction increments have been observed with LHRF. The H-mode co-rotation is correlated with the pedestal temperature gradient, which itself is enhanced by the LH waves absorbed in the plasma periphery. The H-mode counter-rotation increment, a flattening of the peaked velocity profile in the core, is consistent with a reduction in the momentum pinch correlated with a steepening of the core density profile. Most of these rotation changes must be due to indirect transport effects of LH waves on various parameters, which modify the momentum flux.

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Advances in lower hybrid current drive technology on Alcator C-Mod

Cited by 15 publications

References 20 publications

Alcator C-Mod: research in support of ITER and steps beyond

Alcator C-Mod: research in support of ITER and steps beyond

20 years of research on the Alcator C-Mod tokamak

Effects of LHRF on toroidal rotation in Alcator C-Mod plasmas

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