Neoclassical theory for rotation and impurity transport in tokamaks with neutral beam injection

Stacey, Weston M.

doi:10.1063/1.1324664

Cited by 15 publications

(5 citation statements)

References 23 publications

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“…The neoclassical impurity transport theory in axisymmetric devices has been discussed extensively in the literature [21][22][23][24]. A comprehensive review of the collisional theory was given by Hirshman and Sigmar [21] and recently the moment approach was extended to the model including general source and sink terms in the force balance equations, which is applicable to tokamaks with arbitrary collisionality and aspect ratio [22].…”

Section: Neoclassical Impurity Transportmentioning

confidence: 99%

“…A comprehensive review of the collisional theory was given by Hirshman and Sigmar [21] and recently the moment approach was extended to the model including general source and sink terms in the force balance equations, which is applicable to tokamaks with arbitrary collisionality and aspect ratio [22]. On the other hand, a self-consistent neoclassical theory for impurity transport in tokamaks has been developed by Stacey and Sigmar [23,24]. However, there are few reports for impurity transport in nonaxisymmetric devices, which were mainly discussed in the long mean free path regimes [25].…”

Section: Neoclassical Impurity Transportmentioning

confidence: 99%

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Impurity behaviour in LHD long pulse discharges

Nakamura

Takeiri

Peterson

et al. 2002

Plasma Phys. Control. Fusion

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Intrinsic impurity behaviour in neutral beam heated LHD long pulse discharges with a discharge duration of 10 s was investigated. Spectroscopic and bolometric measurements showed a remarkable temporal increase of core radiation due to metallic impurities. Central impurity accumulation was found in a narrow plasma density region ( ne = 1-3 × 10 19 m −3 ) for both density ramp-up discharges and constant density discharges. In the density ramp-up discharges, high-Z impurities were accumulated in the low-density region and diffused out from the core plasma in the high-density region. The impurity behaviour was compared with neoclassical predictions.

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Section: Neoclassical Impurity Transportmentioning

confidence: 99%

Section: Neoclassical Impurity Transportmentioning

confidence: 99%

Impurity behaviour in LHD long pulse discharges

Nakamura

Takeiri

Peterson

et al. 2002

Plasma Phys. Control. Fusion

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“…It is under investigation to confirm the modification of neoclassical impurity transport by using DKES/ PENTA code with an external momentum source, including the change of E r in high power discharges. On the other hand, for tokamak plasmas, the effect of NBI momentum input on neoclassical transport has been reported in several papers [24][25][26]. Radial impurity transport fluxes are produced by the direct momentum exchange between injected beam particles and impurities or the radial electric field obtained from momentum balance.…”

Section: Discussionmentioning

confidence: 99%

Strong suppression of impurity accumulation in steady-state hydrogen discharges with high power NBI heating on LHD

et al. 2017

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Strong suppression of impurity accumulation is observed in long pulse hydrogen discharges with high power NBI (Neutral Beam Injection) heating (P nbi > 10 MW) on the Large Helical Device (LHD), even in impurity accumulation window where the intrinsic impurities such as Fe and C are always accumulated into the plasma core. Density scan experiments in these discharges demonstrate a new operational regime without impurity accumulation in steady state hydrogen discharges. Impurity pinch decreases with increasing ion temperature gradient and carbon Mach number. The peaking of the measured carbon profiles shows strong anti-correlations with the Mach number and its radial gradient. An external torque has a big impact on impurity transport and strong co-current rotation leads to an extremely hollow carbon profile, so-called 'impurity hole' observed in high ion temperature modes. Impurity pinch in the plasmas with net zero torque input (balanced NBI injection) is also strongly reduced by increasing ion temperature gradient, which can drive turbulent modes. The combination effect of turbulence and toroidal rotation plays an important role in the impurity transport.

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“…Previous works have considered modifications to the species particle flux due to a direct effect of external sources of momentum [15][16][17][18] and a simplified model for the anomalous part of the stress tensor. The result found was that externally applied momentum injection could lead to a net outward impurity flux, under certain conditions.…”

Section: Introductionmentioning

confidence: 99%

Impurity outward particle flux from externally applied torque

Fable,

Angioni

2023

Plasma Phys. Control. Fusion

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In this work a term in the impurity particle flux expression, which arises from the externally applied angular momentum torque, is rederived and analyzed in detail. This contribution to the species particle flux is found to be directed outward for co-current injected torque in conditions pertinent to present devices, which could explain the increasing hollowness of light impurity density profiles observed experimentally as neutral beam injected power is increased. This result is obtained by revisiting the fluid framework to compute the particle flux of a generic ion species.

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Neoclassical theory for rotation and impurity transport in tokamaks with neutral beam injection

Abstract: A self-consistent, first-principles neoclassical theory for rotation and impurity transport in tokamaks is presented. The implications of this theory for impurity transport in a tokamak are illustrated by a model problem calculation.

Cited by 15 publications

References 23 publications

Impurity behaviour in LHD long pulse discharges

Impurity behaviour in LHD long pulse discharges

Strong suppression of impurity accumulation in steady-state hydrogen discharges with high power NBI heating on LHD

Impurity outward particle flux from externally applied torque

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