P. Martin

University of Padua

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i-10 index

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Co-Authors

L. Marrelli

National Agency for New Technologies, Energy and Sustainable Economic Development

G. Spizzo

National Agency for New Technologies, Energy and Sustainable Economic Development

P. Franz

National Agency for New Technologies, Energy and Sustainable Economic Development

P. Piovesan

National Centre for Nuclear Research

T. Bolzonella

National Agency for New Technologies, Energy and Sustainable Economic Development

M. Gobbin

National Agency for New Technologies, Energy and Sustainable Economic Development

D. Terranova

National Agency for New Technologies, Energy and Sustainable Economic Development

M. Valisa

National Agency for New Technologies, Energy and Sustainable Economic Development

R. Pasqualotto

National Agency for New Technologies, Energy and Sustainable Economic Development

R. Paccagnella

National Agency for New Technologies, Energy and Sustainable Economic Development

Cooperative Institutions

Max Planck Institute for Plasma Physics

714

Max Planck Society

580

National Agency for New Technologies, Energy and Sustainable Economic Development

393

Culham Science Centre

354

Royal Military Academy

299

Culham Centre for Fusion Energy

284

CEA Cadarache

280

University of Padua

208

École Polytechnique Fédérale de Lausanne

205

Max Planck Innovation

187

Author Statistics

Papers

Citation

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Research Field

Observation of tearing mode deceleration and locking due to eddy currents induced in a conducting shell

Physics of Plasmas (2004)

B. E. Chapman Richard Fitzpatrick D. Craig P. Martin G. Spizzo

Growth to large amplitude of a single core-resonant tearing mode in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch is accompanied by braking and eventual cessation of mode rotation. There is also a concurrent deceleration of bulk plasma rotation. The mode deceleration is shown to be well described by a time-dependent version of a magnetohydrodynamical model [R. Fitzpatrick et al., Phys. Plasmas 6, 3878 (1999)] in which a braking torque originates from eddy currents induced by the rotating mode in the conducting shell surrounding the plasma. According to the model, the electromagnetic braking torque is localized to the plasma in the immediate vicinity of the mode’s resonant surface, but viscosity transfers the torque to the rest of the plasma. Parametrizing the plasma viscous momentum diffusivity in terms of the global momentum confinement time, the model is used to predict both the momentum confinement time and the time evolution of the decelerating mode velocity. In both respects, the model is quite consistent with experimental data.

Reversed field pinch

Momentum diffusion

Momentum (technical analysis)

Tearing

10.1063/1.1689353

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Citations (41)

Trapped particles in the RFP single helicity States

IEEE Transactions on Plasma Science (2005)

I. Predebon L. Marrelli R. B. White P. Martin

Images of the trapped particle fraction in single helicity states of the reversed field pinch configuration are presented. This study is carried out with the Hamiltonian Monte Carlo code ORBIT. The various kinds of trajectories strongly influence radial particle transport in the core, and are determined by field shape and perturbation strength.

Helicity

Reversed field pinch

Hamiltonian (control theory)

10.1109/tps.2005.845333

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Citations (0)

High current regimes in RFX-mod

Plasma Physics and Controlled Fusion (2008)

M. Valisa T. Bolzonella P. Buratti L. Carraro R. Cavazzana

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 Ohmical helical symmetry, with the new magnetic axis helically twisting around the geometrical axis of the torus. The separatrix of the island disappears leaving a wide and symmetric thermal structure with large gradients in the electron temperature profile. The new topology still displays an intermittent nature but its overall presence has reached 85% of the current flat-top period. The large gradients in the electron temperature profile appear to be marginal for the destabilization of ion temperature gradient modes on the assumption that ions and electrons have the same gradients. There are indications that higher currents could provide the conditions under which to prove the existence of a true helical equilibrium as the standard RFP configuration.

Reversed field pinch

Electron temperature

10.1088/0741-3335/50/12/124031

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Citations (46)

UV imaging of a plasma for space applications

HAL (Le Centre pour la Communication Scientifique Directe) (2004)

F. Bonomo P. Franz G. Spizzo L. Marrelli P. Martin

Astrophysical plasma

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Citations (0)

A 3D approach to equilibrium, stability and transport studies in RFX-mod improved regimes

Plasma Physics and Controlled Fusion (2010)

D. Terranova D. Bonfiglio Allen H. Boozer W.A. Cooper M. Gobbin

The full three-dimensional (3D) approach is now becoming an important issue for all magnetic confinement configurations. It is a necessary condition for the stellarator but also the tokamak and the reversed field pinch (RFP) now cannot be completely described in an axisymmetric framework. For the RFP the observation of self-sustained helical configurations with improved plasma performances require a better description in order to assess a new view on this configuration. In this new framework plasma configuration studies for RFX-mod have been considered both with tools developed for the RFP as well as considering codes originally developed for the stellarator and adapted to the RFP. These helical states are reached through a transition to a very low/reversed shear configuration leading to internal electron transport barriers. These states are interrupted by MHD reconnection events and the large Te gradients at the barriers indicate that both current and pressure driven modes are to be considered. Furthermore the typically flat Te profiles in the helical core have raised the issue of the role of electrostatic and electromagnetic turbulence in these reduced chaos regions, so that a stability analysis in the correct 3D geometry is required to address an optimization of the plasma setup. In this view the VMEC code proved to be an effective way to obtain helical equilibria to be studied in terms of stability and transport with a suite of well tested codes. In this work, the equilibrium reconstruction technique as well as the experimental evidence of 3D effects and their first interpretation in terms of stability and transport are presented using both RFP and stellarator tools.

Reversed field pinch

Plasma stability

10.1088/0741-3335/52/12/124023

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Citations (36)

Feedback Stabilization of Multiple Resistive Wall Modes

Physical Review Letters (2004)

P. R. Brunsell D. Yadikin D. Gregoratto R. Paccagnella T. Bolzonella

Active feedback stabilization of multiple independent resistive wall modes is experimentally demonstrated in a reversed-field pinch plasma. A reproducible simultaneous suppression of several nonresonant resistive wall modes is achieved. Coupling of different modes due to the limited number of the feedback coils is observed in agreement with theory. The feedback stabilization of nonresonant RWMs also has an effect on tearing modes that are resonant in the central plasma, leading to a significant prolongation of the discharge pulse.

Resistive touchscreen

Tearing

Reversed field pinch

Negative feedback

10.1103/physrevlett.93.225001

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Citations (91)

Tomographic imaging of resistive mode dynamics in the Madison Symmetric Torus reversed-field pinch

Physics of Plasmas (2006)

P. Franz L. Marrelli P. Piovesan I. Predebon F. Bonomo

A detailed study of the dynamics and magnetic topological effects of resistive-tearing modes is presented for different operational regimes in the Madison Symmetric Torus reversed-field pinch [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. Soft-x-ray tomography and magnetic measurements, along with numerical reconstruction of magnetic-field lines with the ORBIT code [R. B. White and M. S. Chance, Phys. Fluids 27, 2455 (1984)], have been employed. Magnetic-mode dynamics has been investigated in standard plasmas during the transition to the quasi-single helicity state, in which a single mode dominates the mode spectrum. Single helical soft-x-ray structures are studied with tomography in these cases. These structures are associated with magnetic islands, indicating that helical flux surfaces appear in the plasma. Mode dynamics has also been examined during auxiliary inductive current drive, the goal of which is to reduce the tearing-mode amplitudes. In this case the phenomenology of the soft-x-ray structures appearing in the plasma is more complex. In fact, when a quasi-single helicity spectrum occurs, a single island bigger than in the standard case is usually found. On the other hand, when all modes decrease, two helical soft-x-ray structures are observed, with the same helicity as the two innermost resonant modes. This constitutes the first direct evidence of magnetic-chaos reduction during auxiliary inductive current drive, which is responsible for the achievement of the best confinement in the reversed-field pinch configuration up to now.

Reversed field pinch

Helicity

Magnetic helicity

Tearing

10.1063/1.2160519

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Citations (31)

Ultraviolet tomography of kink dynamics in a magnetoplasmadynamic thruster

Physics of Plasmas (2005)

F. Bonomo P. Franz G. Spizzo L. Marrelli P. Martin

In this paper the results of a project concerning the ultraviolet (UV) imaging of a plasma for space applications, produced in a magneto-plasmadynamic (MPD) thruster, are presented. MPD are a class of high-power electric space propulsion devices that accelerate a plasma to high velocities (>10km∕s), by exploiting the Lorentz force. This force arises from the interaction between the discharge electrical current and a self induced and externally applied magnetic field. The imaging system has been realized by inserting three arrays of UV-enhanced photodiodes directly into the plastic structure of the anode. The amplifiers are miniaturized and built into the detector. This advanced diagnostic design allows for a detailed tomographic reconstruction of the emissivity spatial structure, both in the axial direction z (corresponding to a wave number n) and azimuthal direction (wave number m) with high time resolution. A magneto-hydrodynamic instability, with mode numbers m=1 and n=1 has been observed, which might affect the performances of the thruster.

Lorentz force

Photodiode

Kink instability

10.1063/1.2012108

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Citations (11)

Electromagnetic Forces and Mechanical Stresses in the Vacuum Vessel for ASDEX Upgrade

Symposium On Fusion Technology (1982)

O. Jandl H. Kotzlowski P. Martin Felix Werner

ASDEX Upgrade (UG) is a divertor experiment now being designed at IPP Garching. Its aim is to study the plasma-wall interaction and impurity control under reactor-relevant plasma boundary conditions.

ASDEX Upgrade

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Citations (1)

Spontaneous transition to quasi-single helicity states in RFX-mod and MST

P. Piovesan A. Alfier F. Bonomo A. Cravotta P. Franz

Helicity

Mod

Source

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Citations (0)