Experimental investigation and validation of neutral beam current drive for ITER through ITPA Joint Experiments

Suzuki, Takahiro; Akers, R.; Gates, D.; Günter, S.; Heidbrink, W. W.; Hobirk, J.; Luce, T. C.; Murakami, M.; Park, J. M.; Turnyanskiy, M.; experts,

doi:10.1088/0029-5515/51/8/083020

Cited by 25 publications

(19 citation statements)

References 23 publications

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“…The work reported here is a continuation of previous work, in both modeling and experiment, on the use of offaxis neutral beam injection [15][16][17][18][19] and on increasing the b N stability limit through broadening of the current and pressure profiles. Modeling of the effect of broadening the pressure profile is discussed in Refs.…”

Section: Introductionmentioning

confidence: 80%

Progress toward fully noninductive discharge operation in DIII-D using off-axis neutral beam injection

et al. 2013

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The initial experiments on off-axis neutral beam injection into high noninductive current fraction (f NI ), high normalized pressure (b N ) discharges in DIII-D [J. L. Luxon, Fusion Sci. Technol. 48, 828 (2005)] have demonstrated changes in the plasma profiles that increase the limits to plasma pressure from ideal low-n instabilities. The current profile is broadened and the minimum value of the safety factor (q min ) can be maintained above 2 where the profile of the thermal component of the plasma pressure is found to be broader. The off-axis neutral beam injection results in a broadening of the fast-ion pressure profile. Confinement of the thermal component of the plasma is consistent with the IPB98(y,2) scaling, but global confinement with q min > 2 is below the ITER-89P scaling, apparently as a result of enhanced transport of fast ions. A 0-D model is used to examine the parameter space for f NI ¼ 1 operation and project the requirements for high performance steady-state discharges. Fully noninductive solutions are found with 4 < b N < 5 and bootstrap current fraction near 0.5 for a weak shear safety factor profile. A 1-D model is used to show that a f NI ¼ 1 discharge at the top of this range of b N that is predicted stable to n ¼ 1, 2, and 3 ideal MHD instabilities is accessible through further broadening of the current and pressure profiles with off-axis neutral beam injection and electron cyclotron current drive. V C 2013 AIP Publishing LLC.

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Section: Introductionmentioning

confidence: 80%

Progress toward fully noninductive discharge operation in DIII-D using off-axis neutral beam injection

et al. 2013

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“…These cases occur during off-axis NBCD scenarios and they are summarized in Ref. 6. ASDEX Upgrade observes 43 absolute levels of off-axis NBCD that are smaller than the expected values based on neoclassical theory.…”

Section: A Experiments and Modelingmentioning

confidence: 96%

“…Indeed, reviews of the status of energetic ion research have evolved from basic principles 4 to a focus on Alfvénic physics. 5 A recent joint experiment 6 conducted through the International Tokamak Physics Activity (ITPA) directed attention to the possibility that microturbulence significantly enhances neutral beam ion diffusion in cases of off-axis neutral beam current drive (NBCD). Conceptually, this occurs because off-axis neutral beam injection places a large population of beam ions in the mid-radius region of the plasma where microturbulence is strong.…”

Section: Introductionmentioning

confidence: 99%

Energetic ion transport by microturbulence is insignificant in tokamaks

et al. 2013

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Energetic ion transport due to microturbulence is investigated in magnetohydrodynamic-quiescent plasmas by way of neutral beam injection in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. A range of on-axis and off-axis beam injection scenarios are employed to vary relevant parameters such as the character of the background microturbulence and the value of E b =T e , where E b is the energetic ion energy and T e the electron temperature. In all cases, it is found that any transport enhancement due to microturbulence is too small to observe experimentally. These transport effects are modeled using numerical and analytic expectations that calculate the energetic ion diffusivity due to microturbulence. It is determined that energetic ion transport due to coherent fluctuations (e.g., Alfvén eigenmodes) is a considerably larger effect and should therefore be considered more important for ITER. V C 2013 AIP Publishing LLC.

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“…[45], the outermost beam, with R tan =130 cm, provides substantial off-axis neutral beam current drive (NBCD). Note that off-axis NBCD has been observed in conventional aspect ratio tokamaks [50][51][52][53][54], as well as STs [55].…”

Section: : the Nstx-upgrade Facilitymentioning

confidence: 99%

“…The neutral beam current drive [50][51][52][53][54][55][62][63][64] is computed by the NUBEAM code [65]; 8000 to 16000 particles were typically used in these simulations, weighted toward the plasma core to reduce the Monte-Carlo noise on the central beam current drive (wghta=10 [65]). The beam-current shielding factor derived by Lin-Liu & Hinton [64] is used.…”

Section: Free-boundary Transp Simulationsmentioning

confidence: 99%

Exploration of the equilibrium operating space for NSTX-Upgrade

Gerhardt¹,

André²,

Ménard³

2012

Nucl. Fusion

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This paper explores a range of high-performance equilibrium scenarios achievable with neutral beam heating in the NSTX-Upgrade device (Menard J.E. 2012 Nucl. Fusion 52 083015). NSTX-Upgrade is a substantial upgrade to the existing NSTX device (Ono M. et al 2000 Nucl. Fusion 40 557), with significantly higher toroidal field and solenoid capabilities, and three additional neutral beam sources with significantly larger current-drive efficiency. Equilibria are computed with free-boundary TRANSP, allowing a self-consistent calculation of the non-inductive current-drive sources, the plasma equilibrium and poloidal-field coil currents, using the realistic device geometry. The thermal profiles are taken from a variety of existing NSTX discharges, and different assumptions for the thermal confinement scalings are utilized. The no-wall and ideal-wall n = 1 stability limits are computed with the DCON code. The central and minimum safety factors are quite sensitive to many parameters: they generally increase with large outer plasma-wall gaps and higher density, but can have either trend with the confinement enhancement factor. In scenarios with strong central beam current drive, the inclusion of non-classical fast-ion diffusion raises qmin, decreases the pressure peaking, and generally improves the global stability, at the expense of a reduction in the non-inductive current-drive fraction; cases with less beam current drive are largely insensitive to additional fast-ion diffusion. The non-inductive current level is quite sensitive to the underlying confinement and profile assumptions. For instance, for BT = 1.0 T and Pinj = 12.6 MW, the non-inductive current level varies from 875 kA with ITER-98y,2 thermal confinement scaling and narrow thermal profiles to 1325 kA for an ST specific scaling expression and broad profiles. Scenarios are presented which can be sustained for 8–10 s, or (20–30) τCR, at βN = 3.8–4.5. The value of qmin can be controlled at either fixed non-inductive fraction of 100% or fixed plasma current, by varying which beam sources are used, opening the possibility for feedback control of the current profile. In terms of quantities like collisionality, neutron emission, non-inductive fraction, or stored energy, these scenarios represent a significant performance extension compared with NSTX and other present spherical torii.

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Experimental investigation and validation of neutral beam current drive for ITER through ITPA Joint Experiments

Cited by 25 publications

References 23 publications

Progress toward fully noninductive discharge operation in DIII-D using off-axis neutral beam injection

Progress toward fully noninductive discharge operation in DIII-D using off-axis neutral beam injection

Energetic ion transport by microturbulence is insignificant in tokamaks

Exploration of the equilibrium operating space for NSTX-Upgrade

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