V . Antoni

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Intermittency in fluid turbulence can be evidentiated through the analysis of Probability Distribution Functions (PDF) for velocity fluctuations, which display a strong non–gaussian behavior at small scales. In this paper we investigate the occurrence of intermittency in plasma turbulence by studying the departure from the gaussian distribution of PDF for(More)
Coherent structures identified in two reversed field pinch experiments are interpreted as a dynamic balance of dipolar and monopolar vortices growing and evolving under the effect of the ExB flow shear. For the first time their contribution to the anomalous transport has been estimated in fusion related plasmas, showing that they can account for up to 50%(More)
Two Neutral Beam Injectors (NBI) are foreseen to provide a substantial fraction of the heating power necessary to ignite thermonuclear fusion reactions in ITER. The development of the NBI system at unprecedented parameters (40 A of negative ion current accelerated up to 1 MV) requires the realization of a full scale prototype, to be tested and optimized at(More)
In order to test the self-organized criticality (SOC) paradigm in transport processes, a novel technique has been applied for the first time to plasmas confined in reversed field pinch configuration. This technique consists of an analysis of the probability distribution function of the times between bursts in density fluctuations measured by microwave(More)
A statistical analysis of the anomalous particle flux in the edge region of the RFX experiment has revealed that laminar times between bursts, which account for more than 50% of the losses, have a power law distribution and that flux fluctuations are not self-similar. These properties are found in contrast with a wide class of self-organized-criticality(More)
Turbulent structures detected in the edge plasma of fusion devices, often described as blobs, are generally believed to be responsible for confinement degradation. Recent experimental evidence and theories have suggested their filamentary electromagnetic nature. In this Letter the first direct experimental measurements of the parallel current density(More)
Optimization of machine operation, including plasma position control, density control and especially feedback control on multiple magnetohydrodynamic modes, has led RFX-mod to operate reliably at 1.5 MA, the highest current ever achieved on a reversed field pinch (RFP). At high current and low density the magnetic topology spontaneously self-organizes in an(More)
Measurements of magnetic and electrostatic fluctuations in an applied field magneto-plasma-dynamic thruster have shown that a m/n=1/1 kink mode becomes unstable whenever the Kruskal-Shafranov limit is violated. A positive correlation is established between the kink and performance degradation at high current, which has until now prevented the use of this(More)
The results leading to the identification of coherent structures emerging from the background turbulence in the edge region of the reversed field pinch experiments EXTRAP-T2R and RFX are reviewed. These structures have traits of vortices in velocity field and blobs in density, and the reconstruction of their spatial structure and of their time evolution is(More)
In view of the realization of the negative ion beam injectors for ITER, a test facility, named SPIDER, is under construction in Padova (Italy) to study and optimize production and extraction of negative ions. The present paper is devoted to the analysis of the expected first operations of SPIDER in terms of single-beamlet and multiple-beamlet simulations of(More)