S. Cappello
A5088254306- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Quantum chaos and dynamical systems
- Fusion materials and technologies
- Geomagnetism and Paleomagnetism Studies
- Physics of Superconductivity and Magnetism
- Quantum, superfluid, helium dynamics
- Astro and Planetary Science
- Particle Accelerators and Free-Electron Lasers
- Characterization and Applications of Magnetic Nanoparticles
- Fluid Dynamics and Turbulent Flows
- Advanced Thermodynamics and Statistical Mechanics
- Modular Robots and Swarm Intelligence
- Cold Atom Physics and Bose-Einstein Condensates
- Plasma and Flow Control in Aerodynamics
- Laser-induced spectroscopy and plasma
- Dust and Plasma Wave Phenomena
- Theoretical and Computational Physics
- Advanced Frequency and Time Standards
- Gas Dynamics and Kinetic Theory
National Agency for New Technologies, Energy and Sustainable Economic Development
2015-2024
University of Padua
2015-2024
Institute for the Science and Technology of Plasmas
2022-2024
University of Rome Tor Vergata
2024
Princeton Plasma Physics Laboratory
2013
Princeton University
2013
Los Alamos National Laboratory
2013
Oak Ridge National Laboratory
2011
Consorzio Roma Ricerche
2000
Institute of Ionized Gas
1992-2000
Abstract An overview is presented of the progress since 2021 in construction and scientific programme preparation Divertor Tokamak Test (DTT) facility. Licensing for building has been granted at end 2021. Cat. A radiologic source also 2022. The toroidal field magnet system progressing. prototype 170 GHz gyrotron produced it now under test on FALCON design vacuum vessel, poloidal coils civil infrastructures completed. shape first DTT divertor agreed with EUROfusion to different plasma exhaust...
The reversed field pinch (RFP) is a configuration for plasma magnetic confinement. It has been traditionally viewed as dominated by bath of MHD instabilities producing chaos and high energy transport. We report experimental results which go beyond this view. They show decrease the formation coherent helical structure in plasma, whose imaging temperature profile are provided first time. These quasi-single-helicity states observed both transiently stationary conditions. last case consistent...
Reversed field pinch (RFP) sustainment is studied in the framework of three dimensional magnetohydrodynamic (MHD) numerical simulations. The scaling law for magnetic fluctuation amplitude with Lundquist number S delta B approximately=S-0.22, which can be understood if basic dynamic processes are governed by current sheet reconnection. Quasi-periodic oscillations fact found to correlated presence localized currents, sufficiently large make major contribution average power dissipated...
We report the results of an experimental and theoretical international project dedicated to study quasi-single helicity (QSH) reversed field pinch (RFP) plasmas. The has involved several RFP devices numerical codes. It appears that QSH spectra are a robust feature common all experiments. Our expand reinforce evidence formation self-organized states with one dominant helical mode (Ohmic SH state) is approach complementary active control magnetic turbulence improve confinement in steady state RFP.
A scaling approach to the simplest viscoresistive MHD model reveals that Prandtl number acts only through inertia term. When this term is negligible dynamics ruled by Hartmann H only. This occurs for reversed field pinch as seen numerical simulation of model. large system in a multiple helicity state. In vicinity = 2500 displays temporal intermittency with laminar phases quasi-single-helicity (SH) type. For lower H's two basins SH are shown coexist. regimes interest because their nonchaotic...
In this paper numerical results of three-dimensional (3-D) resistive magnetohydrodynamic (MHD) plasma simulations are presented. A system coupled nonlinear differential equations is evolved in time over a significant fraction the macroscopic diffusion scale. The dynamical evolution resembles main features famous Lorenz system. fact, sensitivity MHD on initial distribution spectral energy and stochastic oscillations phase space have been found. At least two dynamic attractors motion...
The RFX-mod machine (Sonato et al 2003 Fusion Eng. Des. 66 161) recently achieved, for the first time in a reversed-field pinch, high plasma current up to 1.6 MA with good confinement. Magnetic feedback control of magnetohydrodynamic instabilities was essential reach goal. As is raised, spontaneously accesses new helical state, starting from turbulent multi-helical conditions. Together this raise, ratio between dominant and secondary mode amplitudes increases continuous way. This brings...
RFX-mod is a Reversed Field Pinch device that allowed performing experiments in regimes with plasma current up to 2 MA, thanks its MHD active control system. Experiments have shown improved performances are obtained when the resonant part of m = 1 spectrum one dominant tearing mode much higher than other secondary ones (quasi single helicity states). Tearing modes play crucial role determining energy and particle transport. Based on present understanding interplay between passive conductive...
The resilience to chaotic perturbations of one-parameter one-degree-of-freedom Hamiltonian dynamics is shown increase when its corresponding separatrix vanishes due a saddle-node bifurcation. This first highlighted for the magnetic chaos related quasisingle helicity (QSH) states reversed field pinch. It provides rationale confinement improvement helical structures experimentally found QSH plasmas; such feature would not be expected from classical resonance overlap picture as disappearance...
Within the framework of MHD modelling RFP is shown to develop turbulent or laminar regimes switching from former latter in a continuous way depending on strength dissipative forces (the higher they are more corresponding regime). In either these cases interesting features can be observed such as occurrence quasi-periodic relaxation events involving reconnection processes, formation stationary helical symmetric configurations. The first case corresponds conventional dynamo where perturbations...
Magnetic field lines and the corresponding particle orbits are computed for a typical chaotic magnetic provided by magnetohydrodynamics numerical simulation of reversed-field pinch. The $m=1$ modes phase locked produce toroidally localized bulging plasma which increases transport. $m=0$ chaos implying poor confinement. However, they also allow formation islands induce transport barriers inside reversal surface.
RFX-mod is a reversed field pinch (RFP) experiment equipped with system that actively controls the magnetic boundary. In this paper we describe results of new control algorithm, clean mode (CMC), in which aliasing sideband harmonics generated by discrete saddle coils corrected real time. CMC operation leads to smoother (i.e. more axisymmetric) Tearing modes rotate (up 100 Hz) and partially unlock. Plasma–wall interaction diminishes due decrease non-axisymmetric shift plasma column. With...
We report the first nonlinear three-dimensional magnetohydrodynamic (MHD) numerical simulations of reversed-field pinch (RFP) that exhibit a systematic repetition quasisingle helicity states with same dominant mode in between reconnection events. This distinctive feature experimental self-organized helical RFP plasmas is reproduced MHD at low dissipation by allowing modulation plasma magnetic boundary similar to one. Realistic amplitudes and topology are also found.
This paper reports experimental results showing that coherent helical structures are formed in the reversed field pinch (RFP) self-organizing plasma core as a result of transitions to states where n-spectrum m=1 modes is dominated by single (1,nmax) geometrical helicity. These dubbed quasi-single helicity (QSH) states. Their magnetic and thermal properties measured reverse experiment (RFX) [G. Rostagni, Fusion Eng. Des. 25, 301 (1995)] device described. The present theoretical understanding...
Optimization of machine operation, including plasma position control, density control and especially feedback on multiple magnetohydrodynamic modes, has led RFX-mod to operate reliably at 1.5 MA, the highest current ever achieved a reversed field pinch (RFP). At high low magnetic topology spontaneously self-organizes in an Ohmical helical symmetry, with new axis helically twisting around geometrical torus. The separatrix island disappears leaving wide symmetric thermal structure large...
With the exploration of MA plasma current regime in up to 0.5 s long discharges, RFX-mod has opened new and very promising perspectives for reversed field pinch (RFP) magnetic configuration, made significant progress understanding improving confinement controlling stability. A big leap with respect previous knowledge expectations on RFP physics performance been by since last 2006 IAEA Fusion Energy Conference. self-organized helical equilibrium experimentally achieved (the Single Helical...
The reversed field pinch configuration is characterized by the presence of magnetic structures both in core and at edge: core, high plasma current spontaneous development a helical structure accompanied appearance internal electron transport barriers; edge strong pressure gradients, identifying an barrier, are observed too, related to position reversal surface.
In the reversed field pinch RFX-mod strong electron temperature gradients develop when Single-Helical-Axis regime is achieved. Gyrokinetic calculations show that in region of microtearing instabilities are dominant turbulent mechanism acting on ion Larmor radius scale. The quasi-linear evaluation thermal conductivity good agreement with experimental estimates.
New edge diagnostics and detailed analysis of magnetic topology have significantly improved the comprehension processes developing at boundary a reversed-field pinch (RFP) plasma in RFX-mod ( = 0.46 m, R 2 m). An upper critical density n C ≈ 0.4 G Greenwald density) is found to limit operational space for quasi-single helical (QSH) regime: reconstructions diagnostic observations suggest that this due plasma–wall interaction which determines toroidally poloidally localized accumulation...
RFX-mod [Sonato et al., Fusion Eng. Des. 66, 161 (2003)] exploits its 192 active coils in both reversed-field pinch (RFP) and tokamak configurations with varying degrees of 3D shaping, providing also a test bed for validating stellarator codes nonlinear magnetohydrodynamic codes. This makes unique flexible facility comparative studies on shaping control. The paper discusses how fields allow access to RFP advanced regimes. are used feedback control Single Helicity (SH) equilibria 1/7 helicity...
Nonlinear fluid modelling predictions of qualitatively new self-organized helical states in the reversed-field pinch configuration are confirmed by experiments RFX-mod device. The realized using a seed edge magnetic field, which can impose its pitch to whole plasma. In simulations, we show increased order and reduced transport field lines regimes with twist non-resonant mode. We reveal existence Cantori, encompassing region characterized conserved surfaces, act as barriers lines. This opens...
Stationary 3D equilibria can form in fusion plasmas via saturation of magnetohydrodynamic (MHD) instabilities or stimulated by external fields. In these cases the current profile is anomalously broad due to magnetic flux pumping produced MHD modes. Flux plays an important role hybrid tokamak plasmas, maintaining minimum safety factor above unity and thus removing sawteeth. It also enables steady-state operation, redistributing non-inductive driven near center electron cyclotron waves. A...
Abstract The RFX-mod2 installation is planned to be completed by 2024 and the start of operations expected in 2025. high flexibility machine (already tested previous RFX-mod experiment) allows operation Reversed Field Pinch tokamak configuration as well ultra-low q pulses. In this work we present predictive analysis on transport, performances plasma control view first experimental campaigns.
The origin of the dynamo velocity field reversed pinch within visco-resistive MHD modeling is uncovered. main component this an electrostatic drift. corresponding related to a small charge separation which consistent with quasineutrality approximation, and should be present in real plasmas, too. While quite natural stationary single helicity state, analysis shown extend also nonstationary multiple regime. Numerical simulations provide spatial distribution fields separation.