The experimental determination of the radial electric field Er and the associated E × B drift velocity at the edge of RFX is presented and possible mechanisms responsible for its generation are discussed. Er measurements by means of an array of Langmuir probes and those deduced from Doppler spectroscopy of impurity lines agree fairly well. In particular the rotation velocity of the plasma edge has been determined from the Doppler shift of a C III emission line. The observation of other ions characterised by different radial positions, such as B IV and C V, has allowed an estimate of the velocity shear. Typical values of plasma rotation at the edge are around 10 km/s while the velocity shear is of the order of (105-106)s-1 in the spontaneous layer, a few cm thick, usually observed in standard discharges. Plasma rotation has been artificially modified by both positive and negative edge biasing and the associated increase or decrease of the fluid velocity is well in agreement with the radial electric field change. The modification of Er during edge biasing and Pulsed Poloidal Current Drive (PPCD) are also reported and interpreted within a momentum balance model. Analytical and self-consistent Monte Carlo models at the plasma edge suggest that impurities have a relevant role in the generation of the radial electric field, due to their relatively large Larmor radius.

Antoni, V., Bartiromo, R., Carraro, L., Desideri, D., Martines, E., Puiatti, M., et al. (2000). Experimental measurements and modelling of the structure of the radial electric field in RFX. CZECHOSLOVAK JOURNAL OF PHYSICS, 50(12), 1387-1396 [10.1023/A:1022843529120].

Experimental measurements and modelling of the structure of the radial electric field in RFX

Martines E;
2000

Abstract

The experimental determination of the radial electric field Er and the associated E × B drift velocity at the edge of RFX is presented and possible mechanisms responsible for its generation are discussed. Er measurements by means of an array of Langmuir probes and those deduced from Doppler spectroscopy of impurity lines agree fairly well. In particular the rotation velocity of the plasma edge has been determined from the Doppler shift of a C III emission line. The observation of other ions characterised by different radial positions, such as B IV and C V, has allowed an estimate of the velocity shear. Typical values of plasma rotation at the edge are around 10 km/s while the velocity shear is of the order of (105-106)s-1 in the spontaneous layer, a few cm thick, usually observed in standard discharges. Plasma rotation has been artificially modified by both positive and negative edge biasing and the associated increase or decrease of the fluid velocity is well in agreement with the radial electric field change. The modification of Er during edge biasing and Pulsed Poloidal Current Drive (PPCD) are also reported and interpreted within a momentum balance model. Analytical and self-consistent Monte Carlo models at the plasma edge suggest that impurities have a relevant role in the generation of the radial electric field, due to their relatively large Larmor radius.
Articolo in rivista - Articolo scientifico
reversed field pinch; RFP; RFX; velocity shear; edge biasing;
English
1387
1396
10
Antoni, V., Bartiromo, R., Carraro, L., Desideri, D., Martines, E., Puiatti, M., et al. (2000). Experimental measurements and modelling of the structure of the radial electric field in RFX. CZECHOSLOVAK JOURNAL OF PHYSICS, 50(12), 1387-1396 [10.1023/A:1022843529120].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/365825
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