Observation of ion cyclotron range of frequencies mode conversion plasma flow drive on Alcator C-Mod

Lin, Y.; Rice, J. E.; Wukitch, S.J.; Greenwald, M.; Hubbard, A.; Ince‐Cushman, A.; Lin, L.; Marmar, E.; Porkoláb, M.; Reinke, M.L.; Tsujii, N.; Wright, J. C.; Team, Jet

doi:10.1063/1.3082936

Cited by 46 publications

(58 citation statements)

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“…324 Simulations with the TORIC code showed that the mechanism is through IC wave interaction with He 3 ions, while the shorter wavelength IBW only caused electron heating. 325 316 conversion regime. Although the stored energy increase is somewhat larger for the minority heating case, the toroidal rotation is much greater for mode conversion.…”

Section: B Icrf Flow Drivementioning

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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Section: B Icrf Flow Drivementioning

confidence: 99%

20 years of research on the Alcator C-Mod tokamak

et al. 2014

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“…This is especially important for extrapolations to next generation devices, in which the effectiveness of NBI is expected to be diminished. As such, these devices will depend more heavily on alternate heating schemes such as ion and electron wave heating and current drive, both of which have been observed experimentally to impact the plasma rotation [23,24,25,26,27,28,29]. In particular, the influence of electron heating on plasma rotation remains unclear.…”

Section: Introductionmentioning

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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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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“…[15,16]). Although no consistent theoretical framework yet exists that solidly links the experimental evidence of flow driven on the one hand and the fate of the energy carried by the up-down asymmetric mode converted waves on the other hand, many believe that one of the main roles externally launched ICRF waves may play in future machines is to ensure flow drive which impacts on plasma confinement and stability.…”

Section: Introductionmentioning

confidence: 99%

Minority and mode conversion heating in (³He)–H JET plasmas

Eester¹,

Lerche²,

Johnson³

et al. 2012

Plasma Phys. Control. Fusion

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Radio frequency (RF) heating experiments have recently been conducted in JET (3 He)-H plasmas. This type of plasmas will be used in ITER's non-activated operation phase. Whereas a companion paper in this same PPCF issue will discuss the RF heating scenario's at half the nominal magnetic field, this paper documents the heating performance in ( 3 He)-H plasmas at full field, with fundamental cyclotron heating of 3 He as the only possible ion heating scheme in view of the foreseen ITER antenna frequency bandwidth. Dominant electron heating with global heating efficiencies between 30% and 70% depending on the 3 He concentration were observed and mode conversion (MC) heating proved to be as efficient as 3 He minority heating. The unwanted presence of both 4 He and D in the discharges gave rise to 2 MC layers rather than a single one. This together with the fact that the location of the high-field side fast wave (FW) cutoff is a sensitive function of the parallel wave number and that one of the locations of the wave confluences critically depends on the 3 He concentration made the interpretation of the results, although more complex, very interesting: three regimes could be distinguished as a function of X[ 3 He] < 5%) in which the RF performance is degrading and ultimately becoming very poor, and finally (iii) a good heating regime at 3 He concentrations beyond 6%. In this latter regime, the heating efficiency did not critically depend on the actual concentration while at lower concentrations (X[ 3 He] < 4%) a bigger excursion in heating efficiency is observed and the estimates differ somewhat from shot to shot, also depending on whether local or global signals are chosen for the analysis. The different dynamics at the various concentrations can be traced back to the presence of 2 MC layers and their associated FW cutoffs residing inside the plasma at low 3 He concentration. One of these layers is approaching and crossing the low-field side plasma edge when 1.8 < X[ 3 He] < 5%. Adopting a minimization procedure to correlate the MC positions with the plasma composition reveals that the different behaviors observed are due to contamination of the plasma. Wave modeling not only supports this interpretation but also shows that moderate concentrations of D-like species significantly alter the overall wave behavior in 3 He-H plasmas. Whereas numerical modeling yields quantitative information on the heating efficiency, analytical work gives a good description of the dominant underlying wave interaction physics.

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Observation of ion cyclotron range of frequencies mode conversion plasma flow drive on Alcator C-Mod

Abstract: Abstract. At modest3 He levels (n 3He /n e ~ 8-12%), in relatively low density D( 3 He) plasmas, e n ≤

Cited by 46 publications

References 45 publications

20 years of research on the Alcator C-Mod tokamak

20 years of research on the Alcator C-Mod tokamak

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

Minority and mode conversion heating in (³He)–H JET plasmas

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Observation of ion cyclotron range of frequencies mode conversion plasma flow drive on Alcator C-Mod

Abstract: Abstract. At modest3 He levels (n 3He /n e ~ 8-12%), in relatively low density D( 3 He) plasmas, e n ≤

Cited by 46 publications

References 45 publications

20 years of research on the Alcator C-Mod tokamak

20 years of research on the Alcator C-Mod tokamak

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

Minority and mode conversion heating in (3He)–H JET plasmas

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Minority and mode conversion heating in (³He)–H JET plasmas