Correlation between Electron Transport and Shear Alfvén Activity in the National Spherical Torus Experiment

Stutman, D.; Delgado‐Aparicio, L.; Gorelenkov, N. N.; Finkenthal, M.; Fredrickson, E.; Kaye, S. M.; Mazzucato, E.; Tritz, K.

doi:10.1103/physrevlett.102.115002

Cited by 78 publications

(107 citation statements)

References 22 publications

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“…Microtearing modes have since been found in conventional aspect ratio tokamak plasmas [19,20], and a nonlinear microtearing mode saturation theory estimate of χ e was found to be consistent with NSTX measurements [21]. Electron heat transport was observed to increase dramatically with rising beam power in the core of NSTX, where fast particle instabilities were observed and thermal temperature gradients were too low to drive transport via the usual mechanisms [22]. Microtearing modes, fast particle instabilities, and sonic flows will not be addressed further in this paper.…”

Section: Confinement Transport and Gyrokinetic Studies Of Stsmentioning

confidence: 66%

Gyrokinetic simulations of spherical tokamaks

Roach

Abel

Akers

et al. 2009

Plasma Phys. Control. Fusion

167

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Abstract. This paper reviews transport and confinement in spherical tokamaks (STs) and our current physics understanding that is partly based on gyrokinetic simulations. We show that equilibrium flow shear can sometimes entirely suppress ion scale turbulence in today's STs. Advanced nonlinear simulations of electron temperature gradient (ETG) driven turbulence, including kinetic ion physics, collisions and equilibrium flow shear, support the model that ETG turbulence can explain electron heat transport in many ST discharges.

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Section: Confinement Transport and Gyrokinetic Studies Of Stsmentioning

confidence: 66%

Gyrokinetic simulations of spherical tokamaks

Roach

Abel

Akers

et al. 2009

Plasma Phys. Control. Fusion

167

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“…69(a). 163 The radial electron temperature profile instead broadens with the NBI power, indicating greatly enhanced electron thermal diffusivity in the core with the applied NBI power as shown in Fig. 69(b).…”

Section: Anomalous Electron Thermal Energy Transport By Gaesmentioning

confidence: 94%

“…162 In addition, there are energetic-particle-driven global and compressional Alfv en eigenmodes (GAE and CAE), which can also affect power deposition and electron energy transport in the plasma core region. 163 In terms of drive and stabilization mechanisms, electron beta b e and collisionality e/i are important parameters as illustrated in Fig. 62.…”

Section: A Motivation For St Researchmentioning

confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

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“…The high frequency instability observed in NSTX [2,3] had k ∥ qR ≫ 1. Assuming that this condition is satisfied, we approximate the Bessel function as J…”

Section: Energy Channelling and Electron Heat Transport (Quasilinear mentioning

confidence: 99%

“…In experiments on both W7-AS and NSTX the instabilities affected the heat transport but had no visible influence on the particle transport. In addition, NSTX experiments have shown that the effect of the Alfvénic activity on the plasma heat transport can differ at different locations: the calculated heat conductivity coefficient increases with injected power in the core region and decreases at the periphery [2,3]. Another peculiarity of the NSTX data is that the anomalous heat transport correlates only with high frequency instabilities (0.5 ÷ 1.1 MHz).…”

Section: Introductionmentioning

confidence: 99%

Effects of energetic-ion-driven instabilities on plasma heating, transport and rotation in toroidal systems

et al. 2010

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Abstract. A theory is developed from which it follows that energetic-ion-driven instabilities can, first, channel the energy of the energetic ions outside the region where these ions are located and, second, considerably affect the electron heat flux across the magnetic field. A new mechanism of the frequency chirping is revealed. Namely, it is shown that instabilities caused by the energetic ions can influence the plasma rotation, in which case the development of the instabilities results in variation of the Doppler shift in time. It is concluded that a key factor responsible for the mentioned phenomena is the local imbalance of the wave emission by energetic ions and the wave absorption by electrons along the radius. On the basis of the developed theory, experiments on the stellarator Wendelstein 7-AS and the spherical torus NSTX, where effects of Alfvénic activity on the plasma temperature were observed, are considered. Effects of energetic-ion-driven instabilities2

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Correlation between Electron Transport and Shear Alfvén Activity in the National Spherical Torus Experiment

Cited by 78 publications

References 22 publications

Gyrokinetic simulations of spherical tokamaks

Gyrokinetic simulations of spherical tokamaks

Recent progress on spherical torus research

Effects of energetic-ion-driven instabilities on plasma heating, transport and rotation in toroidal systems

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