The impact of radial electric fields and plasma rotation on intermittence in TJ-II

Carreras, B. A.; Garcia, L.; Grenfell, G.; Voldiner, I.; Hidalgo, C.

doi:10.1088/1361-6587/ac54e9

Cited by 2 publications

(1 citation statement)

References 19 publications

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“…Given the limitations of this numerical model, the numerical calculations do not constitute a full and detailed simulation of these TJ-II plasmas, although they do reproduce many of their salient features. For more details, please refer to [27].…”

Section: Modellingmentioning

confidence: 99%

Rational surfaces, flows and radial structure in the TJ-II stellarator

et al. 2022

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In this work, we perform a rotational transform scan in the TJ-II stellarator, while measuring several turbulent quantities well inside the plasma edge by means of a Langmuir probe and applying a radial electric field to the edge plasma using a biasing probe. By calculating the intermittence parameter from floating potential measurements, we are able to identify a major low order rational surface and hence relate the probe measurements to the local value of the rotational transform. Based on the former, we are able to show that the poloidal plasma velocity (and hence radial electric field) has a significant radial structure that is clearly related to the rotational transform profile and in particular the lowest order rational surfaces in the range studied. The poloidal velocity is also affected by the edge biasing. The particle flux Γ was also found to exhibit a radial pattern, as did the flow shear suppression term ωE×B, but their relation to the low-order rational surfaces was less clear. We surmise that this lack of direct correspondence is due to an unknown term in the turbulence evolution equation: the instability growth rate, γ. We make use of a reduced Magnetohydrodynamic turbulence model to interpret the results. Overall, a picture is obtained in which the plasma self-organizes towards a state with a clear radial pattern of the radial electric field, in line with expectations from some numerical studies describing the spontaneous formation of an ‘E × B staircase’, consistence of alternating layers with fast and slow radial transport. In this state, profiles of various quantities (density, temperature, pressure) will not be smooth.

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Section: Modellingmentioning

confidence: 99%

Rational surfaces, flows and radial structure in the TJ-II stellarator

et al. 2022

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The performance of equilibrium radial electric field shear on microturbulence with different magnetic shears in tokamak plasmas

Chen

Qin

Sun

et al. 2023

Plasma Phys. Control. Fusion

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Global gyrokinetic particle simulations show that equilibrium radial electric field (Er) shear reduces the linear growth rate, ion heat conductivity, and nonlinear turbulence amplitude for both the ion temperature gradient (ITG) and kinetic ballooning mode (KBM) microturbulence with tilting the poloidal mode structure. Increase in the magnetic shear enhances the stabilizing performance of the Er shear on linear growth rate for ITG case but has no effect on that for KBM case. The radial correlation length of the ITG turbulence is decreased by increasing the magnetic shear in a weak ion diamagnetic flow shear condition with low β, leading to a reduction in effective ExB shearing rate, which weakens the suppression performance of the Er shear on ITG turbulence amplitude. In contrast, under a larger ion diamagnetic flow shear for higher β, increase in magnetic shear strengthens the suppression performance of the Er shear on KBM turbulence amplitude due to increase in the effective shearing rate by increasing the radial correlation length of the turbulence.

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The impact of radial electric fields and plasma rotation on intermittence in TJ-II

Cited by 2 publications

References 19 publications

Rational surfaces, flows and radial structure in the TJ-II stellarator

Rational surfaces, flows and radial structure in the TJ-II stellarator

The performance of equilibrium radial electric field shear on microturbulence with different magnetic shears in tokamak plasmas

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