Magnetic perturbations as a viable tool for edge turbulence modification

Vianello, N.; Rea, Cristina; Agostini, M.; Cavazzana, R.; Ciaccio, G.; Masi, G.; Martines, E.; Mazzi, A.; Momo, B.; Spizzo, G.; Scarin, P.; Spolaore, M.; Zanca, P.; Zuin, M.; Carraro, L.; Innocente, P.; Marrelli, L.; Puiatti, M. E.; Terranova, D.

doi:10.1088/0741-3335/57/1/014027

Cited by 21 publications

(29 citation statements)

References 45 publications

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“…The use of a helical angle to map data of E r in a frame of reference traveling with the mode, as it is done e.g. in the stellarator or, more recently, in the RFX-mod [17,19], could be useful for this purpose.…”

Section: Maps Of Plasma Potential: Experiments and Simulationsmentioning

confidence: 99%

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

et al. 2015

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The electrostatic response of the edge plasma to a magnetic island induced by resonant magnetic perturbations to the plasma edge of the circular limiter tokamak TEXTOR is analyzed. Measurements of plasma potential are interpreted with simulations with the Hamiltonian guiding center code Orbit. We find a strong correlation between the magnetic field topology and the poloidal modulation of the measured plasma potential. The ion and electron drifts yield a predominantly electron driven radial diffusion when approaching the island X-point while ion diffusivities are generally an order of magnitude smaller. This causes a strong radial electric field structure pointing outward from the island O-point. The good agreement found between measured and modeled plasma potential connected to the enhanced radial particle diffusivities supports that a magnetic island in the edge of a tokamak plasma can act as convective cell. We show in detail that the particular, non-ambipolar drifts of electrons and ions in a 3D magnetic topology account for theseeffects. An analytical model for the plasma potential is implemented in the code Orbit, and analyses of ion and electron radial diffusion show that both ion-and electron-dominated transport regimes can exist, which are known as ion and electron root solutions in stellarators. This finding and comparison with reversed field pinch studies and stellarator literature suggests that the role of magnetic islands as convective cells and hence as major radial particle transport drivers could be a generic mechanism in 3D plasma boundary layers.

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Section: Maps Of Plasma Potential: Experiments and Simulationsmentioning

confidence: 99%

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

et al. 2015

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“…We will focus on the role of electrostatic fluctuations in edge transport mechanisms by describing how this specific transport channel can be affected by the application of external 3D fields. We will see that the electrostatic fluxes turn out to be modulated around the O-point and the X-point of the outermost island, therefore the flux modulation in the presence of resonant MP fields is a common physical feature despite the different magnetic geometry, accordingly to what has been discussed in [20,22]. Furthermore, we will provide information about the typical transverse wave numbers of the fluctuations of electrostatic particle and energy fluxes in both the RFP and the tokamak configuration.…”

Section: Introductionmentioning

confidence: 63%

Comparative studies of electrostatic turbulence induced transport in presence of resonant magnetic perturbations in RFX-mod

et al. 2015

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Three-dimensional non-axisymmetric magnetic fields are purposely applied to toroidally symmetric fusion plasmas in order to modify transport of heat and particle fluxes to the plasma-facing components (PFCs), and specifically to control and suppress Edge Localized Modes (ELMs) in H-mode tokamak plasmas. This paper presents a comparative study between two magnetic configurations available in the RFX-mod device, namely the original reversed-field pinch configuration and the more recent low-field circular ohmic tokamak. The object of this study is the chaotic edge, which is spontaneous in the RFP configuration and induced by externally applied magnetic perturbations (MPs) in the tokamak. The analogy between the RFX-mod reversed-field pinch and tokamak configuration is developed through experiments with externally applied Resonant Magnetic Perturbations (RMPs). A detailed study of the underlying magnetic topology in both configurations is given through the field line tracing code FLiT. The electrostatic flux profiles turn out to be modulated around the O-point and X-point of the magnetic islands driven by the externally applied perturbations. Furthermore, the evidence of transport induced by small-scale electrostatic turbulence is discussed and the transverse wave numbers characterizing it are identified.

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“…The negative electrode biasing induced in a quite reproducible way the H-mode achievement. Two EX/P5-24 4 reperesentative shots were chosen, #39101 and #39135 respectively, operated in Deuterium. An example of plasma features modifications induced by negative electrode biasing is shown in fig.…”

Section: H-mode Achievement In Rfx-mod Tokamakmentioning

confidence: 99%

“…This system represents the state of the art of MHD mode feedback control [2]. It allows a noticeable flexibility, so that the magnetic boundary can be effectively controlled and modulated by applying resonant or non-resonant magnetic perturbations (MP) both in RFP and in tokamak configurations [3,4]. The application of MPs is widely studied in the fusion community as a promising tool in particular to limit the impact of ELMs on plasma facing components [5].…”

Section: Introductionmentioning

confidence: 99%

H-mode achievement and edge features in RFX-mod tokamak operation

Spolaore¹,

Cavazzana²,

Marrelli³

et al. 2017

Nucl. Fusion

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The RFX-Mod experiment is a fusion device designed to operate as a Reversed Field Pinch (RFP), with a major radius R " 2 m and a minor radius a " 0.459 m. Its high versatility recently allowed operating also as an ohmic tokamak allowing comparative studies between the two configurations in the same device. The device is equipped with a state of the art MHD mode feedback control system, providing a magnetic boundary effective control and modulation, by applying resonant or nonresonant magnetic perturbations (MP) both in RFP and in tokamak configurations. In the fusion community the application of MPs is widely studied as a promising tool in particular to limit the impact of plasma filaments and ELMs, in particular on plasma facing components. An important issue is envisaged in the exploitation of the RFX-Mod active control system for ELM mitigation studies.As a first step in this direction, this paper will focus on the most recent achievements in term of RFX-Mod tokamak explored scenarios, which allowed the first investigation of the ohmic and edge biasing induced H-mode. In particular the realization of D-shaped tokamak discharges and the design and deployment of an insertable polarized electrode were accomplished. Both operations took advantage of the implementation of a real-time feedback control system of the electron density and of a multivariable shape feedback control system designed on a full modelbased approach. Indications of Ohmic H-mode were transiently observed during Single Null shaped plasmas. Stationary H-mode phases were instead obtained with insertable electrode biasing stimulation. The edge biasing is applied in new operation scenarios relatively unexplored with this technique in particular in plasma shaped Single Null discharges and in the very low-q circular plasma discharges, qpaq ă 2, achievable in RFX-Mod. Important modification of the edge plasma density and flow properties are observed as well as, in some cases, a complex "dithering" phenomenology, characterized by very fast L-H and H-L transitions. These strong fluctuations appear associated to the onset of MHD activity, whose behaviour will be analyzed and discussed in the paper along with the filamentary structures observed in the fast turbulence electromagnetic fluctuations.Published as a journal article in Nuclear Fusion http://iopscience.iop.org/article/Abstract The RFX-mod experiment is a fusion device designed to operate as a Reversed Field Pinch (RFP), with a major radius R= 2 m and a minor radius a = 0.459 m. Its high versatility recently allowed operating also as an ohmic tokamak allowing comparative studies between the two configurations in the same device. The device is equipped with a state of the art MHD mode feedback control system, providing a magnetic boundary effective control, by applying resonant or non-resonant magnetic perturbations (MP) both in RFP and in tokamak configurations. In the fusion community the application of MPs is widely studied as a promising tool to limit the impact of plasma filaments and ELMs on p...

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Magnetic perturbations as a viable tool for edge turbulence modification

Cited by 21 publications

References 45 publications

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

Comparative studies of electrostatic turbulence induced transport in presence of resonant magnetic perturbations in RFX-mod

H-mode achievement and edge features in RFX-mod tokamak operation

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