Parallel and perpendicular flows in the RFX-mod edge region

Spolaore, M.; Vianello, N.; Agostini, M.; Bonfiglio, D.; Cavazzana, R.; Lorenzini, R.; Martines, E.; Momo, B.; Scarin, P.; Serianni, G.; Spagnolo, S.; Zuin, M.

doi:10.1016/j.jnucmat.2010.12.029

Cited by 6 publications

(11 citation statements)

References 24 publications

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“…The perpendicular flow radial profile ( fig. 3b) seems to show a slightly different behaviour (as its time evolution during the F-steps), anyway the profile shape is comparable with the same quantity measured by the Uprobe [11].…”

Section: Discussion Of the Experimental Resultssupporting

confidence: 72%

“…3), another insertable system, dubbed "U-probe" [11], located 30˚toroidally far from the Gundestrup one, has been used to reconstruct the electron temperature radial profile and time evolution, together with the density fluctuations.…”

Section: Experimental Equipmentmentioning

confidence: 99%

“…In fig.1 the radial profile of the plasma flow parallel component M par , carried out through the ion saturation current measurements (for the explored insertions with this configuration), has been compared with both magnetized and unmagnetized model based on the floating potential measurements, and a reasonable agreement has been found. The radial profile of the perpendicular component M perp for the same models has been compared with the v E×B flow (in fig.3b both profiles have been overplotted), measured by the U-probe [10], computing the radial derivative of the plasma potential, v E×B = (-dV p (r)/dr)/B [11]. Also in this case the profiles appear to be compatible, supporting the reliability of the method based on Gundestrup probe collecting V fl signals.…”

Section: Model Validationmentioning

confidence: 99%

“…Specifically, a step in the reversal parameter F has been induced during the discharge to compare different magnetic equilibria: a phase with a shallow reversal (F > -0.07) and a phase with deeper reversal (F < −0.15) [11]. An example is shown in fig.4, together with the time evolution of the parallel and perpendicular flow M par , M perp and a reconstruction of the local magnetic topology (Poincaré plots) obtained with the FLiT code [14] at three different time instants.…”

Section: Time Evolutionmentioning

confidence: 99%

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Flow Measurements in the Edge Region of the RFX‐Mod Experiment

Spolaore

Cavazzana

Innocente

et al. 2010

Contrib. Plasma Phys.

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In this contribution a detailed study of the edge flow properties performed on the outer region of the RFX-mod experiment using a Gundestrup probe is presented. In particular, both parallel and perpendicular components (with respect to the magnetic field) have been evaluated in several low current discharges providing a complete reconstruction of the edge flow profiles.Different methods based on both magnetized and unmagnetized models have been used to evaluate the averaged plasma flow components and their time variations. Furthermore, configurations involving either ion saturation current signals or floating potential ones have been used to evaluate both parallel and perpendicular flow components and a good agreement has been found between different methods.Finally, the dynamic behaviour of edge flow fluctuations induced by gradient modifications following pellet injection and by varying the edge magnetic topology (the m = 0 islands radial position) have been studied.

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Section: Discussion Of the Experimental Resultssupporting

confidence: 72%

Section: Experimental Equipmentmentioning

confidence: 99%

Section: Model Validationmentioning

confidence: 99%

Section: Time Evolutionmentioning

confidence: 99%

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Flow Measurements in the Edge Region of the RFX‐Mod Experiment

Spolaore

Cavazzana

Innocente

et al. 2010

Contrib. Plasma Phys.

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“…The fluctuations of the flow exhibit a toroidal ripple whose minima are well correlated with the maximum values of the plasma shift. The same information is also obtained through the GPI diagnostic, which gives an average value of the flow in the last 25 mm of the plasma close to the wall [27,31]. Since the toroidal flow is linked to the radial component of the electric field through v φ = E r /B θ , this experimental result means that E r in the edge also has a toroidal ripple with seven bumps.…”

Section: Magnetic Structure and Flowmentioning

confidence: 53%

Topology and transport in the edge region of RFX-mod helical regimes

et al. 2011

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New edge diagnostics and detailed analysis of magnetic topology have significantly improved the comprehension of the processes developing at the boundary of a reversed-field pinch (RFP) plasma in RFX-mod (a = 0.46 m, R = 2 m). An upper critical density n C ≈ 0.4 n G (n G Greenwald density) is found to limit the operational space for the improved quasi-single helical (QSH) regime: magnetic topology reconstructions and diagnostic observations suggest that this limit is due to a helical plasma–wall interaction which determines toroidally and poloidally localized edge density accumulation and cooling. The experimental evidence is provided by a variety of diagnostics: the magnetic boundary as reconstructed from equilibrium codes reveals a helical deformation, which is well correlated with the modulation of edge pressure profile as reconstructed from the thermal helium beam diagnostic. Correlations with the helical deformation are also observed on the space- and time-resolved patterns of the floating potential measured at the wall, and with the edge plasma flow, obtained from different diagnostics. The relevance of these findings is that understanding the mechanisms that limit the operational space of QSH is decisive in achieving the goal of high-density stationary helical RFP equilibrium.

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