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1. Physics of tearing mode rotation and slow-down in the RFX-mod tokamak.

Author

Cordaro, L., Zanca, P., Zuin, M., Auriemma, F., Fassina, A., Martines, E., Zaniol, B., Cavazzana, R., De Masi, G., Grenfell, G., Momo, B., Spagnolo, S., Spolaore, M., and Vianello, N.

Subjects
TOKAMAKS, PHYSICS, FUSION reactors, ROTATIONAL motion, FLOW measurement
Abstract

We present a study of the fast, spontaneous rotation regime of tearing modes (TM) in the RFX-mod circular tokamak discharges. Integrated analyses of magnetic, flow and kinetic measurements, are discussed. This analysis of rotation frequency components related to the ion flow and diamagnetic drift shows that the TM fast rotation is mainly driven by the diamagnetic drift. The global decrease of the temperature profile, induced by a growing mode amplitude, can explain the slowing-down of the rotation, which in turn can trigger a potentially disruptive sequence. We show that in RFX-mod the slowing-down cannot be explained solely on the basis of the electromagnetic torque with the external conductive structures, as often reported in literature from other experiments. This analysis, indeed, suggests a strong relationship between the TM dynamics and the transport physics. Statistical analysis of disruptions with slowing down of island rotation shows that TMs take a part in the disruption, even without a locking to the wall. [ABSTRACT FROM AUTHOR]

Published
2022
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2. Ion heating and energy balance during magnetic reconnection events in the RFX-mod experiment

Author

Gobbin M., Agostini M., Auriemma F., Carraro L., Cavazzana R., Fassina A., Franz P., Marrelli L., Momo B., Piovan R., Predebon I., Puiatti M.E., Spizzo G., Terranova D., and Zuin M.

Subjects
RFX-mod, Physics::Plasma Physics, magnetic reconnection, ion heating, tokamak, energy balance
Abstract

Reconnection events in high current reversed field pinch plasmas are often associated to the partial or total transitions from a helical topology with conserved flux surfaces to a configuration characterized by a chaotic magnetic field. The electron temperature dynamic together with the magnetic energy reconstructions are used to evaluate the energy balance during these events and to quantify the associated dissipated power and released energy. A fraction of the energy released during reconnection events is involved in ion heating, as estimated by the energy distribution function of neutral atoms, a rather interesting feature in a reactorial perspective.

Published
2021

3. 3D filamentary transport and the role of edge sheared radial electric fields in the RFX-mod tokamak

Author

Grenfell G., Spolaore M., Abate D., Carraro L., Marrelli L., van Milligen B., Predebon I., Spagnolo S., Veranda M., Agostini M., Cavazzana R., Cordaro L., De Masi G., Franz P., Martines E., Momo B., Puiatti M.E., Scarin P., Vianello N., Zaniol B., Zuin M., and RFX-mod Team

Subjects
3D filamentary transport, RFX-Mod, Physics::Plasma Physics, tokamak
Abstract

Sheared radial electric field is an important parameter in regulating cross-field transport in fusiondevices. The edge and scrape-off layer (SOL) turbulence coupling, as well as the parallel dissipation,are responsible for the SOL width maintenance, which, in turn, is a critical parameter for particle andenergy exhaustion in tokamaks \cite{Grenfell:2019}. This coupling is usually attributed to the trans-port of streamers or blobs (also called filaments). They are mostly created in the plasma edge, in highgradient free energy regions, and transported radially by ExB drift. The turbulent filaments prop-erties, e.g. velocity and size, and ultimately their penetration into the SOL, are defined by the typeof instability that generates them as well as how they interact with the background \cite{Myra:2013}.High beta filaments, on the other hand, tend to be more resilient to the background. This is thecase of the Edge-Localized Mode filaments in H-mode regimes, one of the current threats for thefeasibility of future fusion reactors. In this work, we study the filament or blob cross-field transportin the RFX-mod operating as tokamak in different plasma regimes by using a set of electrostatic andmagnetic probes \cite{Grenfell:2018}. It has been shown recently that H-mode ELM-free and ELMyare induced in the RFX-mod tokamak by electrode biasing technique \cite{Spolaore:2017}. We showthat the properties of filaments in these regimes, as well as in L-mode, are distinct. While in L-modeblobs propagate almost freely into the SOL scaling as sheath-connected filaments \cite{Manz:2013},in the ELM-free H-mode, filaments are trapped (their cross-field velocity approaches to zero) and dis-sipated around the plasma boundary, where the ExB shearing rate is marginally comparable to theireffective convective time \cite{Grenfell:2018}. ELMs filaments propagate further into the SOL carry-ing a larger parallel current density associated with the edge transport barrier relaxation.

Published
2019

4. Magnetic perturbations as a viable tool for edge turbulence modification

Author

Vianello N., Rea C., Agostini M., Cavazzana R., Ciaccio G., De Masi G., Martines E., Mazzi A., Momo B., Spizzo G., Scarin P., Spolaore M., Zanca P., Zuin M., Carraro L., Innocente P., Marrelli L., Puiatti M. E., Terranova D., the RFX-mod Team, Vianello, N, Rea, C, Agostini, M, Cavazzana, R, Ciaccio, G, De Masi, G, Martines, E, Mazzi, A, Momo, B, Spizzo, G, Scarin, P, Spolaore, M, Zanca, P, Zuin, M, Carraro, L, Innocente, P, Marrelli, L, Puiatti, M, and Terranova, D

Subjects
Physics, Safety factor, Tokamak, Reversed field pinch, Turbulence, business.industry, turbulence, Perturbation (astronomy), RMP, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Computational physics, Magnetic field, law.invention, electric field, Optics, Nuclear Energy and Engineering, law, Physics::Plasma Physics, 0103 physical sciences, Magnetohydrodynamics, 010306 general physics, business, Phenomenology (particle physics)
Abstract

A complete description of the effects of magnetic perturbation on the edge region of RFX-mod is here reported. The flexibility of the RFX-mod device [1] allows for the operation of the machine both as a reversed field pinch (RFP, with maximum current 2 MA) and as a low-current, circular ohmic tokamak (I-p,I-max = 0.15 MA). The present paper summarizes the most recent results obtained in both configurations with either spontaneous or induced edge radial magnetic perturbation. Emphasis will be devoted to the experimental characterization of the edge flow, focusing on the phase relation between flow and perturbed magnetic field. These informations are provided for natural and stimulated helical discharges in RFPs, and for tokamak safely operated, thanks to the unique RFX-mod MHD control system, in a wide range of edge safety factor 1.9 less than or similar to q(a)

Published
2015
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5. Edge effects of dynamically shaped tokamak configuration in RFX-mod experiment

Author

Spolaore M, Cavazzana R, De Masi G, Finotti C, Kudlacek O, Marchiori G, Martines E, Momo B, Rea C, Spagnolo S, Vianello N, Zuin M, Spolaore, M, Cavazzana, R, De Masi, G, Finotti, C, Kudlacek, O, Marchiori, G, Martines, E, Momo, B, Rea, C, Spagnolo, S, Vianello, N, and Zuin, M

Subjects
RFX-mod, edge plasma, tokamak
Published
2014

6. MHD spectra and coordinate transformations in toroidal systems

Author

Predebon, I., Momo, B., Terranova, D., and Innocente, P.

Subjects
Tokamak, MHD, Coordinate system, Applied magnetic fields, 01 natural sciences, Spectral line, 010305 fluids & plasmas, law.invention, Action-angle coordinates, law, Toroidal Systems, Physics::Plasma Physics, Reversed field pinch plasmas, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Spectral decomposition, Magnetoplasma, 010306 general physics, Physics, Reversed field pinch, Condensed Matter Physics, Spectral properties, Magnetic field, Pinch effect, Classical mechanics, Geometric approaches, Magnetic fields, Physics::Space Physics, Co-ordinate system, Magnetohydrodynamics, Co-ordinate transformation, Reference frame, Vector potential
Abstract

A fully geometric approach is used to study the mutual spectral properties of different classes of MHD equilibria with symmetries defined by action-angle coordinates. We refer mostly to the helical equilibria of tokamak and reversed field pinch plasmas compared to the axisymmetric counterpart. Based on the existence of different coordinate systems, we show how the magnetic field and the vector potential are correspondingly evaluated, and how their spectral decompositions may largely vary. Most notably, a monochromatic perturbation in a reference frame can appear with a rich spectrum in another frame. The consequences on the interpretation of the measurements and the implications on the effectiveness of the externally applied magnetic fields on the plasma are discussed with practical examples.

Published
2016

7. Overview of the RFX fusion science program

Author

M. Gobbin, Roberto Pasqualotto, D. Bonfiglio, Enrico Zilli, Giuseppe Marchiori, Piero Martin, S. Martini, Fulvio Auriemma, E. Gazza, D.K. Mansfield, P. Zaccaria, Piergiorgio Sonato, S. Ortolani, Wolf-Dieter Schneider, D. Yadikin, Stefano Munaretto, L. Piron, M. Valisa, Fabio Sattin, Susanna Cappello, G. V. Perverezev, F. Milani, Roberto Paccagnella, Paolo Bettini, S. Fiameni, Roscoe White, A. Ruzzon, V. Antoni, Leonardo Giudicotti, Yueqiang Liu, Lionello Marrelli, Nicola Vianello, S. Dal Bello, A. Scaggion, V. Rigato, Fabio Villone, A. Zamengo, Federica Bonomo, R. Cavazzana, M. Baruzzo, L. Carraro, F. Fantini, Giuseppe Zollino, Barbara Zaniol, Rita Lorenzini, Luis Chacon, X. Garbet, C. Angioni, Andrea Rizzolo, G. De Masi, G. Rostagni, W. A. Cooper, Manabu Takechi, Piero Agostinetti, Paolo Scarin, A. Pizzimenti, Yongkyoon In, Sheena Menmuir, Silvia Spagnolo, M. Moresco, Satoru Kiyama, S. P. Hirshman, M. Okabayashi, Giuseppe Chitarin, S. C. Guo, Gabriele Manduchi, Dominique Escande, Gianluigi Serianni, Alessandro Fassina, Luca Grando, Simona Barison, Allen H. Boozer, Michael Drevlak, Diego Marcuzzi, M. Pavei, J.Q. Dong, Anton Soppelsa, B. Momo, Gianluca Spizzo, Hajime Sakakita, Neil Pomphrey, Shunsuke Ide, Donald A. Spong, J. S. Sarff, Alessandra Canton, D. Lopez Bruna, M. Brombin, Matteo Zuin, T. Bolzonella, R. Piovan, Songfen Liu, Alberto Ferro, Italo Predebon, V. Igochine, L. Zanotto, Simone Peruzzo, Elena Gaio, P. Piovesan, Cesare Taliercio, J. Adamek, Go Matsunaga, P. Zanca, A. Buffa, M. Veranda, N. Pomaro, M. Spolaore, Oliviero Barana, Francesco Gnesotto, Emilio Martines, M. Dalla Palma, Paolo Franz, David Terranova, Yoichi Hirano, Matteo Agostini, G. Mazzitelli, Alberto Alfier, L. Novello, Vanni Toigo, M. Boldrin, R. Delogu, Guglielmo Rubinacci, Maria Ester Puiatti, A. Fiorentin, Karsten McCollam, E. Spada, M. Cavinato, A. De Lorenzi, L. Apolloni, J. Brotankova, F. Fellin, P. Innocente, Raul Sanchez, Zhirui Wang, Adriano Luchetta, Martin, P, Adamek, J, Agostinetti, P, Agostini, M, Alfier, A, Angioni, C, Antoni, V, Apolloni, L, Auriemma, F, Barana, O, Barison, S, Baruzzo, M, Bettini, P, Boldrin, M, Bolzonella, T, Bonfiglio, D, Bonomo, F, Boozer, A, Brombin, M, Brotankova, J, Buffa, A, Canton, A, Cappello, S, Carraro, L, Cavazzana, R, Cavinato, M, Chacon, L, Chitarin, G, Cooper, W, Dal Bello, S, Dalla Palma, M, Delogu, R, De Lorenzi, A, De Masi, G, Dong, J, Drevlak, M, Escande, D, Fantini, F, Fassina, A, Fellin, F, Ferro, A, Fiameni, S, Fiorentin, A, Franz, P, Gaio, E, Garbet, X, Gazza, E, Giudicotti, L, Gnesotto, F, Gobbin, M, Grando, L, Guo, S, Hirano, Y, Hirshman, S, Ide, S, Igochine, V, In, Y, Innocente, P, Kiyama, S, Liu, S, Liu, Y, Bruna, D, Lorenzini, R, Luchetta, A, Manduchi, G, Mansfield, D, Marchiori, G, Marcuzzi, D, Marrelli, L, Martini, S, Matsunaga, G, Martines, E, Mazzitelli, G, Mccollam, K, Menmuir, S, Milani, F, Momo, B, Moresco, M, Munaretto, S, Novello, L, Okabayashi, M, Ortolani, S, Paccagnella, R, Pasqualotto, R, Pavei, M, Perverezev, G, Peruzzo, S, Piovan, R, Piovesan, P, Piron, L, Pizzimenti, A, Pomaro, N, Pomphrey, N, Predebon, I, Puiatti, M, Rigato, V, Rizzolo, A, Rostagni, G, Rubinacci, G, Ruzzon, A, Sakakita, H, Sanchez, R, Sarff, J, Sattin, F, Scaggion, A, Scarin, P, Schneider, W, Serianni, G, Sonato, P, Spada, E, Soppelsa, A, Spagnolo, S, Spolaore, M, Spong, D, Spizzo, G, Takechi, M, Taliercio, C, Terranova, D, Toigo, V, Valisa, M, Veranda, M, Vianello, N, Villone, F, Wang, Z, White, R, Yadikin, D, Zaccaria, P, Zamengo, A, Zanca, P, Zaniol, B, Zanotto, L, Zilli, E, Zollino, G, Zuin, M, Martin, P., Adamek, J., Agostinetti, P., Agostini, M., Alfier, A., Angioni, C., Antoni, V., Apolloni, L., Auriemma, F., Barana, O., Barison, S., Baruzzo, M., Bettini, P., Boldrin, M., Bolzonella, T., Bonfiglio, D., Bonomo, F., Boozer, A. H., Brombin, M., Brotankova, J., Buffa, A., Canton, A., Cappello, S., Carraro, L., Cavazzana, R., Cavinato, M., Chacon, L., Chitarin, G., Cooper, W. A., Bello, S. D., Palma, M. D., Delogu, R., Lorenzi, A. D., Masi, G. D., Dong, J. Q., Drevlak, M., Escande, D. F., Fantini, F., Fassina, A., Fellin, F., Ferro, A., Fiameni, S., Fiorentin, A., Franz, P., Gaio, E., Garbet, X., Gazza, E., Giudicotti, L., Gnesotto, F., Gobbin, M., Grando, L., Guo, S. C., Hirano, Y., Hirshman, S. P., Ide, S., Igochine, V., In, Y., Innocente, P., Kiyama, S., Liu, S. F., Liu, Y. Q., Bruna, D. L., Lorenzini, R., Luchetta, A., Manduchi, G., Mansfield, D. K., Marchiori, G., Marcuzzi, D., Marrelli, L., Martini, S., Matsunaga, G., Martines, E., Mazzitelli, G., Mccollam, K., Menmuir, S., Milani, F., Momo, B., Moresco, M., Munaretto, S., Novello, L., Okabayashi, M., Ortolani, S., Paccagnella, R., Pasqualotto, R., Pavei, M., Perverezev, G. V., Peruzzo, S., Piovan, R., Piovesan, P., Piron, L., Pizzimenti, A., Pomaro, N., Pomphrey, N., Predebon, I., Puiatti, M. E., Rigato, V., Rizzolo, A., Rostagni, G., Rubinacci, Guglielmo, Ruzzon, A., Sakakita, H., Sanchez, R., Sarff, J. S., Sattin, F., Scaggion, A., Scarin, P., Schneider, W., Serianni, G., Sonato, P., Spada, E., Soppelsa, A., Spagnolo, S., Spolaore, M., Spong, D. A., Spizzo, G., Takechi, M., Taliercio, C., Terranova, D., Toigo, V., Valisa, M., Veranda, M., Vianello, N., Villone, F., Wang, Z., White, R. B., Yadikin, D., Zaccaria, P., Zamengo, A., Zanca, P., Zaniol, B., Zanotto, L., Zilli, E., Zollino, G., and Zuin, M.

Subjects
Nuclear and High Energy Physics, RFX-mod, Tokamak, Nuclear engineering, PLASMAS, CONFINEMENT, reversed field pinch, magnetic confinement, law.invention, law, Physics::Plasma Physics, RFP, Scaling, Mod, Physics, Reversed field pinch, STABILITY, Magnetic confinement fusion, INTERNAL TRANSPORT BARRIER, Plasma, Fusion power, Condensed Matter Physics, REVERSED-FIELD-PINCH, Atomic physics, Magnetohydrodynamics, Stellarator
Abstract

This paper summarizes the main achievements of the RFX fusion science program in the period between the 2008 and 2010 IAEA Fusion Energy Conferences. RFX-mod is the largest reversed field pinch in the world, equipped with a system of 192 coils for active control of MHD stability. The discovery and understanding of helical states with electron internal transport barriers and core electron temperature >1.5 keV significantly advances the perspectives of the configuration. Optimized experiments with plasma current up to 1.8 MA have been realized, confirming positive scaling. The first evidence of edge transport barriers is presented. Progress has been made also in the control of first-wall properties and of density profiles, with initial first-wall lithization experiments. Micro-turbulence mechanisms such as ion temperature gradient and micro-tearing are discussed in the framework of understanding gradient-driven transport in low magnetic chaos helical regimes. Both tearing mode and resistive wall mode active control have been optimized and experimental data have been used to benchmark numerical codes. The RFX programme also provides important results for the fusion community and in particular for tokamaks and stellarators on feedback control of MHD stability and on three-dimensional physics. On the latter topic, the result of the application of stellarator codes to describe three-dimensional reversed field pinch physics will be presented. © 2011 IAEA, Vienna.

Published
2011

8. Physics of tearing mode rotation and slow-down in the RFX-mod tokamak

Author

L. Cordaro, P. Zanca, M. Zuin, F. Auriemma, A. Fassina, E. Martines, B. Zaniol, R. Cavazzana, G. De Masi, G. Grenfell, B. Momo, S. Spagnolo, M. Spolaore, N. Vianello, Cordaro, L, Zanca, P, Zuin, M, Auriemma, F, Fassina, A, Martines, E, Zaniol, B, Cavazzana, R, De Masi, G, Grenfell, G, Momo, B, Spagnolo, S, Spolaore, M, and Vianello, N

Subjects
Nuclear and High Energy Physics, diamagnetic drift, tearing mode, mode rotation, Condensed Matter Physics, tokamak
Abstract

We present a study of the fast, spontaneous rotation regime of tearing modes (TM) in the RFX-mod circular tokamak discharges. Integrated analyses of magnetic, flow and kinetic measurements, are discussed. This analysis of rotation frequency components related to the ion flow and diamagnetic drift shows that the TM fast rotation is mainly driven by the diamagnetic drift. The global decrease of the temperature profile, induced by a growing mode amplitude, can explain the slowing-down of the rotation, which in turn can trigger a potentially disruptive sequence. We show that in RFX-mod the slowing-down cannot be explained solely on the basis of the electromagnetic torque with the external conductive structures, as often reported in literature from other experiments. This analysis, indeed, suggests a strong relationship between the TM dynamics and the transport physics. Statistical analysis of disruptions with slowing down of island rotation shows that TMs take a part in the disruption, even without a locking to the wall.

Published
2022

9. Turbulent filament properties in L and H-mode regime in the RFX-mod operating as a tokamak

Author

L. Carraro, B. Momo, L. Cordaro, Roberto Cavazzana, M. Veranda, I. Predebon, Silvia Spagnolo, C. Hidalgo, P. Scarin, M. Zuin, Lionello Marrelli, Emilio Martines, B. Zaniol, N. Vianello, G. De Masi, M. E. Puiatti, Paolo Franz, Davide Abate, RFX-mod Team, Monica Spolaore, B. Ph. van Milligen, G. Grenfell, Matteo Agostini, Grenfell, G, Spolaore, M, Abate, D, Carraro, L, Marrelli, L, Predebon, I, Spagnolo, S, Veranda, M, Agostini, M, van Milligen, B, Cavazzana, R, Cordaro, L, De Masi, G, Franz, P, Hidalgo, C, Martines, E, Momo, B, Puiatti, M, Scarin, P, Vianello, N, Zaniol, B, Zuin, M, and RFX-mod Team

Subjects
Nuclear and High Energy Physics, Tokamak, blobs, 01 natural sciences, biasing, 010305 fluids & plasmas, law.invention, Protein filament, Physics::Plasma Physics, law, Mod, 0103 physical sciences, magnetic fluctuations, 010306 general physics, filaments, vorticity, Physics, Turbulence, blob, turbulence, Mode (statistics), Biasing, Mechanics, Vorticity, Condensed Matter Physics, H-mode, filament, magnetic fluctuation
Abstract

The dynamics of turbulent filaments in L and ELM-free H-mode in the RFX-mod device operating as a tokamak is discussed in the present work. L-H transition and sustained H-mode have been achieved in the RFX-mod with the aid of an external electrode biasing (Spolaore et al 2017 Nucl. Fusion 57 116039). Through advanced statistical techniques, turbulent filaments are detected and tracked from the edge to the scrape-off layer (SOL) in a two-dimension floating potential map (measured with a 2D array of Langmuir probes) related with extreme events of a fixed ion saturation current signal in the SOL. While in L-mode filaments travel almost freely, their motion becomes restricted to the near SOL during the induced biasing H-mode. In this region, the background shear decorrelation time becomes shorter than the convective filament time, favouring its suppression. However, the experimental observation of a nearly 'trapped' monopole potential points out the possible role of the vortex selection mechanism. The sign and magnitude of the turbulent parallel vorticity are consistent with the E × B background vorticity in the SOL in this regime, while in L-mode, the inferred turbulent vorticity is always above the background one. The sparse filamentary transport in the far SOL during H-mode is further confirmed from the measurements of a poloidally symmetric array of electrostatic sensors on the wall. Lastly, the radial velocity of filaments in both regimes was discussed in the framework of analytical scalings. Filaments in L-mode exhibit a reasonable agreement with the sheath-limited regime in the cold ion approximation, with a non-negligible associated parallel current density measured with a set of 3-axial pick-up coils installed in the probe head. In H-mode, the collisionality increases near the separatrix while filaments seem to follow the inertial regime before become trapped.

Published
2020
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10. Design of embedded electrostatic sensors for the RFX-mod2 device

Author

Roberto Cavazzana, Simone Peruzzo, B. Momo, Nicola Vianello, Nicolò Marconato, M. Bernardi, M. Spolaore, G. De Masi, G. Grenfell, Silvia Spagnolo, Matteo Zuin, Emilio Martines, M. Dalla Palma, Spagnolo, S, Spolaore, M, Bernardi, M, Cavazzana, R, Peruzzo, S, Dalla Palma, M, De Masi, G, Grenfell, G, Marconato, N, Martines, E, Momo, B, Vianello, N, and Zuin, M

Subjects
Tokamak, Plasma diagnostic, probe, 01 natural sciences, Plasma diagnostics, 030218 nuclear medicine & medical imaging, law.invention, 03 medical and health sciences, symbols.namesake, 0302 clinical medicine, Optics, law, 0103 physical sciences, Langmuir probe, Instrumentation, Mathematical Physics, Physics, Toroid, 010308 nuclear & particles physics, business.industry, Plasma, Analysis and statistical methods, probes, Electrostatics, Magnetic Confinement Fusion, Pinch, symbols, Plasma diagnostics - probes, Electric potential, business, Analysis and statistical method
Abstract

RFX-mod experiment is currently under a challenging upgrade of the machine assembly. One of the main purpose of RFX-mod2, the upgraded device, is the achievement of better performances by decreasing the tearing modes amplitude in Reversed-Field Pinch (RFP) configuration thanks to a higher plasma-shell proximity [1, 2]. Moreover, most of the innovations characterizing the device and its diagnostics are conceived with the aim to operate in both RFP and tokamak configurations. This attention on the different configurations is taken into account in the electrostatic sensors design and layout. RFX-mod2 will be equipped with poloidal and toroidal arrays of electrostatic sensors, measuring plasma density and temperature, plasma potential, particle and energy fluxes and floating potential fluctuations. Two toroidal arrays of 72 sensors each (one on the high field side and one on the low field side) are foreseen. Moreover, four poloidal arrays of 28 elements will be housed. A such large amount of sensors is due to the requirement of a better characterization of the numerous instabilities observed in RFP plasma edge, along with the possibility to study the plasma shape in different tokamak configurations (circular, single null, double null). Two different kinds of Langmuir probes configurations will be installed: the so-called single probe and 5-pin balanced triple probe. The conceptual design of the sensors takes inspiration from the model successfully installed on RFX-mod [3], that allows to remove tiles in case of damage, by means of a remote handling manipulator. Each sensor is composed by two parts: the tile side houses pins directly faced to the plasma and connected by springs to the shell side, where specific contacts, conveniently isolated, carry the signals to the cables.

Published
2019

11. H-mode achievement and edge features in RFX-mod tokamak operation

Author

N. Vianello, Roberto Paccagnella, Barbara Zaniol, Paolo Scarin, Emilio Martines, Paolo Franz, G. De Masi, C. Taliercio, C. Piron, Giuseppe Marchiori, S. Dal Bello, L. Zanotto, Roberto Cavazzana, Matteo Zuin, Luca Grando, C. Finotti, Lionello Marrelli, B. Momo, M. E. Puiatti, G. Grenfell, Alberto Ferro, M. Spolaore, Paolo Innocente, P. Piovesan, Lorella Carraro, L. Cordaro, Silvia Spagnolo, M. Recchia, O. Kudlacek, Spolaore, M, Cavazzana, R, Marrelli, L, Carraro, L, Franz, P, Spagnolo, S, Zaniol, B, Zuin, M, Cordaro, L, Dal Bello, S, De Masi, G, Ferro, A, Finotti, C, Grando, L, Grenfell, G, Innocente, P, Kudlacek, O, Marchiori, G, Martines, E, Momo, B, Paccagnella, R, Piovesan, P, Piron, C, Puiatti, M, Recchia, M, Scarin, P, Taliercio, C, Vianello, N, and Zanotto, L

Subjects
ELM filament, Nuclear and High Energy Physics, Tokamak, Edge (geometry), 01 natural sciences, 010305 fluids & plasmas, law.invention, Physics::Plasma Physics, law, 0103 physical sciences, 010306 general physics, SN shape, ELM filaments, Physics, Reversed field pinch, electrode biasing, Biasing, Radius, Plasma, Condensed Matter Physics, Computational physics, electromagnetic measure, H-mode, electromagnetic measures, Magnetohydrodynamics, Current density
Abstract

The RFX-mod experiment is a fusion device designed to operate as a reversed field pinch (RFP), with a major radius R = 2 m and a minor radius a = 0.459 m. Its high versatility recently allowed operating it also as an ohmic tokamak, allowing comparative studies between the two configurations in the same device. The device is equipped with a state of the art MHD mode feedback control system providing a magnetic boundary effective control, by applying resonant or non-resonant magnetic perturbations (MP), both in RFP and in tokamak configurations. In the fusion community the application of MPs is widely studied as a promising tool to limit the impact of plasma filaments and ELMs (edge localized modes) on plasma facing components. An important new research line is the exploitation of the RFX-mod active control system for ELM mitigation studies. As a first step in this direction, this paper presents the most recent achievements in term of RFX-mod tokamak explored scenarios, which allowed the first investigation of the ohmic and edge biasing induced H-mode. The production of D-shaped tokamak discharges and the design and deployment of an insertable polarized electrode were accomplished. Reproducible H-mode phases were obtained with insertable electrode negative biasing in single null discharges, representing an unexplored scenario with this technique. Important modifications of the edge plasma density and flow properties are observed. During the achieved H-mode ELM-like electromagnetic composite filamentary structures are observed. They are characterized by clear vorticity and parallel current density patterns.

Published
2017

12. Turbulent electromagnetic filaments in actively modulated toroidal plasma edge

Author

D. Terranova, G. De Masi, Matteo Zuin, Gianluca Spizzo, Cristina Rea, Paolo Zanca, Paolo Scarin, Silvia Spagnolo, L. Marrelli, M. E. Puiatti, Matteo Agostini, N. Vianello, A. Mazzi, Roberto Cavazzana, B. Momo, Emilio Martines, M. Spolaore, Paolo Innocente, Spolaore, M, Agostini, M, Momo, B, Rea, C, Vianello, N, Zuin, M, Cavazzana, R, De Masi, G, Innocente, P, Marrelli, L, Martines, E, Mazzi, A, Puiatti, M, Spagnolo, S, Spizzo, G, Scarin, P, Terranova, D, and Zanca, P

Subjects
Physics, Nuclear and High Energy Physics, Tokamak, Toroid, magnetic perturbation, Reversed field pinch, Boundary (topology), Mechanics, reversed field pinch, Edge (geometry), Condensed Matter Physics, law.invention, Protein filament, electromagnetic turbulence, law, Physics::Plasma Physics, Beta (plasma physics), magnetic perturbations, plasma vorticity, Atomic physics, tokamak, Topology (chemistry)
Abstract

Filament or blob structures have been observed in all magnetic configurations with very similar features despite the difference in the magnetic geometry, and are believed to play an important role in convecting particles and energy towards the wall. Despite their different generation mechanism, turbulent structures and edge-localized mode (ELM) filaments share some common physical features. The electromagnetic effects on filament structures deserve particular interest, among others reasons for the implication they could have for ELM, related for instance to their dynamics in the transition region between closed and open field lines or to the possibility, at high beta regimes, of causing line bending which could enhance the interaction of blobs with the first wall. A direct characterization of the effects of active modification of the edge topology on EM turbulent filament structures is presented, comparing reversed field pinch and tokamak configurations. Measurements are obtained in the RFX-mod device, which allows operation in both configurations and with different equilibria. The RFX-mod experiment versatility is exploited also from the point of view of the active control of the edge magnetic topology, equipped with an advanced system for edge boundary feedback control. Three different case studies of actively controlled magnetic perturbations are shown, focusing on the filament interaction with local magnetic islands. High-frequency fluctuations, characterizing electrostatic and magnetic filament features, and the associated transport coefficients have been observed to be strongly affected by the island proximity and topology.

Published
2015
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13. Electromagnetic turbulent structures: A ubiquitous feature of the edge region of toroidal plasma configurations

Author

Silvia Spagnolo, N. Vianello, Emilio Martines, Ambrogio Fasoli, Roberto Cavazzana, Ivo Furno, Christian Theiler, Matteo Agostini, J. A. Alonso, A. Scaggion, D. Carralero, G. De Masi, F. Avino, M. Spolaore, Gianluca Spizzo, B. Momo, Paolo Scarin, Matteo Zuin, C. Hidalgo, Spolaore, M, Vianello, N, Furno, I, Carralero, D, Agostini, M, Alonso, J, Avino, F, Cavazzana, R, De Masi, G, Fasoli, A, Hidalgo, C, Martines, E, Momo, B, Scaggion, A, Scarin, P, Spagnolo, S, Spizzo, G, Theiler, C, and Zuin, M

Subjects
Physics, Tokamak, Toroid, Reversed field pinch, WAVES, current filament, Vorticity, Condensed Matter Physics, TRANSPORT, Computational physics, law.invention, Vortex, Physics::Fluid Dynamics, law, Beta (plasma physics), plasma turbulence, electromagnetic structure, Torpex, Atomic physics, PROGRESS, Stellarator
Abstract

Electromagnetic features of turbulent filaments, emerging from a turbulent plasma background, have been studied in four different magnetic configurations: the stellarator TJ-II, the Reversed Field Pinch RFX-mod, a device that can be operated also as a ohmic tokamak, and the Simple Magnetized Torus, TORPEX. By applying an analogous diagnostic concept in all cases, direct measurements of both field-aligned current density and vorticity were performed inside the filament. The inter-machine comparison reveals a clear dependence of the filament vorticity upon the local time-averaged E × B flow shear. Furthermore, a wide range of local beta was explored allowing concluding that this parameter plays a fundamental role in the appearance of filament electromagnetic features.

Published
2015

14. Overview of the RFX-mod fusion science activity

Author

A. De Lorenzi, Rita Lorenzini, F. Belli, Andrea Rizzolo, Luca Stevanato, O. McCormack, Paolo Scarin, D. F. Escande, J. S. Sarff, M. Bigi, Y. Zhang, Alessandro Fassina, L. Piron, N. Vianello, M. E. Puiatti, Roberto Paccagnella, Fabio Villone, Piergiorgio Sonato, Nicola Pilan, Emilio Martines, James D. Hanson, C. Taliercio, A. Zamengo, M. Recchia, L. Giudicotti, M. Vallar, J.Q. Dong, M. Dalla Palma, Daniele Bonfiglio, Paolo Franz, Matthias Komm, Luis Chacon, Satoru Kiyama, N. Visona, M. Siragusa, L. Zanotto, Paolo Bettini, D. Terranova, Raul Sanchez, Roscoe White, S. Dal Bello, M. Brombin, Enrico Zilli, Francesco Gnesotto, Yueqiang Liu, S.P. Hirshman, L. Pigatto, S. Martini, Piero Martin, M. Pavei, Nisarg Patel, Alessandra Canton, Lorenzo Frassinetti, Matteo Zuin, T. Bolzonella, G. Urso, Chenguang Li, Oliver Schmitz, C. Finotti, Paolo Zanca, Chiara Bustreo, Silvia Spagnolo, M. Veranda, M. Baruzzo, V. Antoni, T. Barbui, Hajime Sakakita, Pavlos Xanthopoulos, Wolf-Dieter Schneider, Nicolò Marconato, Yoshiro Narushima, W. A. Cooper, G. Pucella, Piero Agostinetti, Lionello Marrelli, B. Liu, B. Momo, Simone Peruzzo, X. Y. Xu, Elena Gaio, M. Moresco, Francesco Ghezzi, Y. Suzuki, C. Piron, O. Tudisco, Susanna Cappello, P. Piovesan, Adriano Luchetta, A. Maistrello, F. Sattin, M. Boldrin, Donald A. Spong, A. Buffa, L. Cordaro, V. Yanovskiy, R. Cavazzana, Cristina Rea, W. Gonzalez, Matteo Agostini, R. Piovan, Songfen Liu, Giuseppe Chitarin, G. Rostagni, S. M. Deambrosis, Alberto Ferro, O. Kudlacek, M. Spolaore, Gianluca Spizzo, Paolo Innocente, Italo Predebon, G. Mazzitelli, Marco Gobbin, D. Cester, J. L. Jackson, Laszlo Sajo-Bohus, M. Valente, T.C. Luce, L. Laguardia, Diego Marcuzzi, Fulvio Auriemma, Giuseppe Marchiori, P. Vincenzi, D.K. Mansfield, E. Spada, M. Valisa, G. De Masi, Gabriele Manduchi, Lorella Carraro, E. Miorin, M. Okabayashi, S. C. Guo, Barbara Zaniol, R. Delogu, D. Lopez-Bruna, Marco Barbisan, Faa Federico Felici, Cristian Ruset, Luca Grando, R. Bilel, Mazzitelli, G., Tudisco, O., Pucella, G., Zuin, M, DAL BELLO, S, Marrelli, L, Puiatti, M, Agostinetti, P, Agostini, M, Antoni, V, Auriemma, F, Barbisan, M, Barbui, T, Baruzzo, M, Belli, F, Bettini, P, Bigi, M, Bilel, R, Boldrin, M, Bolzonella, T, Bonfiglio, D, Brombin, M, Buffa, A, Bustreo, C, Canton, A, Cappello, S, Carraro, L, Cavazzana, R, Cester, D, Chacon, L, Chitarin, G, Cooper, W, Cordaro, L, DALLA PALMA, M, Deambrosis, S, Delogu, R, De Lorenzi, A, DE MASI, G, Dong, J, Escande, D, Fassina, A, Felici, F, Ferro, A, Finotti, C, Franz, P, Frassinetti, L, Gaio, E, Ghezzi, F, Giudicotti, L, Gnesotto, F, Gobbin, M, Gonzalez, W, Grando, L, Guo, S, Hanson, J, Hirshman, S, Innocente, P, Jackson, J, Kiyama, S, Komm, M, Kudlacek, O, Laguardia, A, Li, C, Liu, B, Liu, S, Liu, Y, López Bruna, D, Lorenzini, R, Luce, T, Luchetta, A, Maistrello, A, Manduchi, G, Mansfield, D, Marchiori, G, Marconato, N, Marcuzzi, D, Martin, P, Martines, E, Martini, S, Mazzitelli, G, Mccormack, O, Miorin, E, Momo, B, Moresco, M, Narushima, Y, Okabayashi, M, Paccagnella, R, Patel, N, Pavei, M, Peruzzo, S, Pilan, N, Pigatto, L, Piovan, R, Piovesan, P, Piron, C, Piron, L, Predebon, I, Pucella, G, Rea, C, Recchia, M, Rizzolo, A, Rostagni, G, Ruset, C, Sajò Bohus, L, Sakakita, H, Sanchez, R, Sarff, J, Sattin, F, Scarin, P, Schmitz, O, Schneider, W, Siragusa, M, Sonato, P, Spada, E, Spagnolo, S, Spolaore, M, Spong, D, Spizzo, G, Stevanato, L, Suzuki, Y, Taliercio, C, Terranova, D, Tudisco, O, Urso, G, Valente, M, Valisa, M, Vallar, M, Veranda, M, Vianello, N, Villone, F, Vincenzi, P, Visonà, N, White, R, Xanthopoulos, P, Xu, X, Yanovskiy, V, Zamengo, A, Zanca, P, Zaniol, B, Zanotto, L, Zhang, Y, and Zilli, E

Subjects
Nuclear and High Energy Physics, Guiding center, Tokamak, MHD, single helicity, reversed field pinch, runaway electron, 01 natural sciences, 010305 fluids & plasmas, law.invention, 3D boundary, Physics::Plasma Physics, law, Electric field, 0103 physical sciences, 010306 general physics, PWI, tokamak, reversed field pinch, tokamak, single helicity, 3D boundary, runaway electrons, MHD, PWI, Physics, Reversed field pinch, runaway electrons, Plasma, Condensed Matter Physics, Computational physics, Magnet, ingle helicity, Pinch, Atomic physics, Magnetohydrodynamics
Abstract

This paper reports the main recent results of the RFX-mod fusion science activity. The RFX-mod device is characterized by a unique flexibility in terms of accessible magnetic configurations. Axisymmetric and helically shaped reversed-field pinch equilibria have been studied, along with tokamak plasmas in a wide range of q(a) regimes (spanning from 4 down to 1.2 values). The full range of magnetic configurations in between the two, the so-called ultra-low q ones, has been explored, with the aim of studying specific physical issues common to all equilibria, such as, for example, the density limit phenomenon. The powerful RFX-mod feedback control system has been exploited for MHD control, which allowed us to extend the range of experimental parameters, as well as to induce specific magnetic perturbations for the study of 3D effects. In particular, transport, edge and isotope effects in 3D equilibria have been investigated, along with runaway mitigations through induced magnetic perturbations. The first transitions to an improved confinement scenario in circular and D-shaped tokamak plasmas have been obtained thanks to an active modification of the edge electric field through a polarized electrode. The experiments are supported by intense modeling with 3D MHD, gyrokinetic, guiding center and transport codes. Proposed modifications to the RFX-mod device, which will enable further contributions to the solution of key issues in the roadmap to ITER and DEMO, are also briefly presented. © 2017 IAEA, Vienna.

Published
2017

15. RFX-mod: A multi-configuration fusion facility for three-dimensional physics studies

Author

Alessandra Canton, Matteo Zuin, D. F. Escande, Roberto Paccagnella, Federica Bonomo, E. Martines, Anton Soppelsa, L. Zanotto, Rita Lorenzini, Alessandro Fassina, M. Baruzzo, Paolo Scarin, Daniele Bonfiglio, Roberto Cavazzana, Barbara Zaniol, M. Veranda, D. Terranova, G. De Masi, Piero Martin, L. Piron, M. E. Puiatti, P. Piovesan, Luis Chacon, N. Vianello, G. Ciaccio, L. Marrelli, Lorella Carraro, Susanna Cappello, Gianluca Spizzo, Marco Gobbin, Paolo Zanca, Paolo Franz, M. Valisa, M. Spolaore, Paolo Innocente, Fulvio Auriemma, Matteo Agostini, B. Momo, Tommaso Bolzonella, Piovesan, P, Bonfiglio, D, Auriemma, F, Bonomo, F, Carraro, L, Cavazzana, R, De Masi, G, Fassina, A, Franz, P, Gobbin, M, Marrelli, L, Martin, P, Martines, E, Momo, B, Piron, L, Valisa, M, Veranda, M, Vianello, N, Zaniol, B, Agostini, M, Baruzzo, M, Bolzonella, T, Canton, A, Cappello, S, Chacon, L, Ciaccio, G, Escande, D, Innocente, P, Lorenzini, R, Paccagnella, R, Puiatti, M, Scarin, P, Soppelsa, A, Spizzo, G, Spolaore, M, Terranova, D, Zanca, P, Zanotto, L, and Zuin, M

Subjects
Physics, RFX-mod, Tokamak, Reversed field pinch, PLASMAS, reversed field pinch, Plasma, Condensed Matter Physics, Helicity, PERTURBATIONS, law.invention, Computational physics, Nonlinear system, law, RFP, Pinch, Magnetohydrodynamic drive, Atomic physics, FIELD, Stellarator
Abstract

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 and 3D nonlinear magnetohydrodynamic codes. This makes RFX-mod a unique and flexible facility for comparative studies on 3D shaping and control. The paper discusses how 3D fields allow access to RFP and tokamak advanced regimes. 3D fields are used to feedback control Single Helicity (SH) RFP equilibria with 1/7 helicity up to similar to 2 MA. They also allow accessing SH regimes with higher density (Greenwald fraction up to 0.5), presently inaccessible in spontaneous SH regimes. Feedback on the 2/1 resistive-wall mode in RFX-mod tokamak plasmas allows for safe operation at q(a) < 2, an almost unexplored promising regime. Forcing the 2/1 mode to saturate at finite but small level, a helical tokamak equilibrium with significant n=1 modulation is produced and a new way to tailor sawteeth is found. The effects of different levels of 3D shaping on momentum transport in both RFP and tokamak helical states are discussed.

Published
2013

16. On the statistics and features of turbulent structures in RFX-mod

Author

Matteo Agostini, M. Zuin, Emilio Martines, Silvia Spagnolo, P. Scarin, B. Momo, G. De Masi, N. Vianello, Roberto Cavazzana, Monica Spolaore, Vianello, N, Spolaore, M, Agostini, M, Cavazzana, R, De Masi, G, Martines, E, Momo, B, Scarin, P, Spagnolo, S, and Zuin, M

Subjects
Tokamak, Similarity (geometry), K-epsilon turbulence model, blobs, reversed field pinch, Enstrophy, 01 natural sciences, 010305 fluids & plasmas, law.invention, Physics::Fluid Dynamics, Physics::Plasma Physics, law, 0103 physical sciences, Statistical physics, 010306 general physics, tokamak, Physics, Reversed field pinch, Turbulence, blob, turbulence, Condensed Matter Physics, Computational physics, Nonlinear Sciences::Chaotic Dynamics, Nuclear Energy and Engineering, Beta (plasma physics), Energy (signal processing)
Abstract

An extensive statistical characterization of the electromagnetic turbulence in the edge region of RFX-mod, operated as a tokamak and as a Reversed Field Pinch, is presented. Striking similarity are observed on the intermittent character of the electrostatic turbulence between the two configurations whereas the difference between magnetic turbulence is likely to be imputed to the different beta value of the two configurations. Blobs are characterized in terms of their spatial structure, the associated enstrophy and energy and the mechanism of energy and enstrophy transfer between intermittent fluctuation at different scales is addressed.

Published
2016

17. Internal and external electron transport barriers in the RFX-mod reversed field pinch

Author

D. F. Escande, S. Dal Bello, B. Momo, L. Zanotto, Tommaso Bolzonella, Rita Lorenzini, F. Sattin, Paolo Scarin, S. C. Guo, Alberto Alfier, L. Novello, M. Baruzzo, Alessandro Fassina, D. Bonfiglio, S. Martini, Fulvio Auriemma, Lorella Carraro, M. E. Puiatti, D. Terranova, Silvia Spagnolo, Matteo Agostini, Marco Gobbin, A. Ruzzon, Susanna Cappello, Alessandra Canton, Matteo Zuin, Emilio Martines, Giuseppe Marchiori, P. Piovesan, Roberto Paccagnella, Paolo Franz, Piero Martin, M. Valisa, Paolo Zanca, M. Veranda, M. Spolaore, E. Gazza, A. Scaggion, L. Marrelli, Italo Predebon, Sheena Menmuir, Gianluca Spizzo, P. Innocente, Federica Bonomo, R. Cavazzana, L. Piron, N. Vianello, Anton Soppelsa, G. De Masi, L. Apolloni, Barbara Zaniol, Puiatti, M, Valisa, M, Agostini, M, Auriemma, F, Bonomo, F, Carraro, L, Fassina, A, Gobbin, M, Lorenzini, R, Momo, B, Scaggion, A, Zaniol, B, Alfier, A, Apolloni, L, Baruzzo, M, Bolzonella, T, Bonfiglio, D, Canton, A, Cappello, S, Cavazzana, R, Dal Bello, S, De Masi, G, Escande, D, Franz, P, Gazza, E, Guo, S, Innocente, P, Marchiori, G, Marrelli, L, Martin, P, Martines, E, Martini, S, Menmuir, S, Novello, L, Paccagnella, R, Piovesan, P, Piron, L, Predebon, I, Ruzzon, A, Sattin, F, Scarin, P, Soppelsa, A, Spizzo, G, Spagnolo, S, Spolaore, M, Terranova, D, Veranda, M, Vianello, N, Zanca, P, Zanotto, L, and Zuin, M

Subjects
Nuclear and High Energy Physics, OHMIC H-MODE, Tokamak, Materials science, RFX-mod, Reversed field pinch, Condensed matter physics, CONFINEMENT, Plasma, reversed field pinch, Condensed Matter Physics, Electron transport chain, law.invention, Shear (sheet metal), law, Plasmas, TOKAMAK, RFP, Electron temperature, OPERATION, Internal heating, transport barrier, Bifurcation
Abstract

An interesting result of magnetic chaos reduction in RFX-mod high current discharges is the development of strong electron transport barriers. An internal heat and particle transport barrier is formed when a bifurcation process changes the magnetic configuration into a helical equilibrium and chaos reduction follows, together with the formation of a null in the q shear. Strong temperature gradients develop, corresponding to a decreased thermal and particle transport. Turbulence analysis shows that the large electron temperature gradients are limited by the onset of micro-tearing modes, in addition to residual magnetic chaos. A new type of electron transport barrier with strong temperature gradients develops more externally (r/a = 0.8) accompanied by a 30% improvement of the global confinement time. The mechanism responsible for the formation of such a barrier is still unknown but it is likely associated with a local reduction of magnetic chaos. These external barriers develop primarily in situations of well-conditioned walls so that they might be regarded as attempts towards an L–H transition. Both types of barriers occur in high-current low-collisionality regimes. Analogies with tokamak and stellarators are discussed.

Published
2011

18. Three-dimensional equilibria and transport in RFX-mod: A description using stellarator tools

Author

Piero Martin, Raul Sanchez, Lionello Marrelli, Marco Gobbin, David Terranova, Dominique Escande, RFX-mod Team, Daniele Bonfiglio, Allen H. Boozer, Gianluca Spizzo, Rita Lorenzini, Emilio Martines, A. W. Cooper, I. Predebon, Neil Pomphrey, Donald A. Spong, B. Momo, S.P. Hirshman, M. E. Puiatti, Jeremy Lore, Gobbin, M, Bonfiglio, D, Boozer, A, Cooper, A, Escande, D, Hirshman, S, Lore, J, Lorenzini, R, Marrelli, L, Martin, P, Martines, E, Momo, B, Pomphrey, N, Predebon, I, Puiatti, M, Sanchez, R, Spizzo, G, Spong, D, and Terranova, D

Subjects
Physics, Tokamak, RFX-mod, Reversed field pinch, STABILITY, Monte Carlo method, PLASMAS, Boundary (topology), reversed field pinch, Collisionality, Condensed Matter Physics, Computational physics, law.invention, quasi-single helicity, PARADIGM, law, Physics::Plasma Physics, REVERSED-FIELD PINCH, Pinch, RFP, Electron temperature, QSH, Statistical physics, Stellarator
Abstract

RFX-mod self-organized single helical axis (SHAx) states provide a unique opportunity to advance 3D fusion physics and establish a common knowledge basis in a parameter region not covered by stellarators and tokamaks. The VMEC code has been adapted to the reversed-field pinch (RFP) to model SHAx equilibria in fixed boundary mode with experimental measurements as constraint. The averaged particle diffusivity over the helical volume, estimated with the Monte Carlo code ORBIT, has a neoclassical-like dependence on collisionality and does not show the 1/ trend of un-optimized stellarators. In particular, the helical region boundary, corresponding to an electron transport barrier with zero magnetic shear and improved confinement, has been investigated using numerical codes common to the stellarator community. In fact, the DKES/PENTA codes have been applied to RFP for local neoclassical transport computations, including radial electric field, to estimate thermal diffusion coefficients in the barrier region for typical RFX-mod temperature and density profiles. A comparison with power balance estimates shows that residual chaos due to secondary tearing modes and small-scale turbulence still contribute to drive anomalous transport in the barrier region. © 2011 American Institute of Physics.

Published
2011

19. Edge density characterization in the RFX-mod experiment using the ultrafast reflectometry technique

Author

Alessandro Fassina, Roberto Cavazzana, M. Moresco, Emilio Martines, G. De Masi, B. Momo, De Masi, G, Cavazzana, R, Fassina, A, Martines, E, Momo, B, and Moresco, M

Subjects
Physics, Nuclear and High Energy Physics, reflectometry, RFX-mod, Field (physics), Edge density, business.industry, MICROWAVE REFLECTOMETRY, BAND FREQUENCY-MODULATION, Topology (electrical circuits), reversed field pinch, Condensed Matter Physics, Sweep frequency response analysis, Characterization (materials science), Optics, Nuclear magnetic resonance, PROFILE MEASUREMENTS, edge density, REVERSED-FIELD PINCH, TOKAMAK, RFP, Reflectometry, business, Ultrashort pulse, Microwave
Abstract

The traditional and widely used reflectometric schemes are not able to probe the edge density layers of the reversed field pinches (RFPs) due to the presence of a high level of density fluctuations. In order to overcome this limitation, an ultrafast microwave reflectometer has been developed and the first Ka-band has been successfully operational on the RFX-mod experiment [1] since mid-2009. The actual diagnostics configuration (frequency sweep 26.5–30.5 GHz in 1 µs) allows us to evaluate the radial distance of the relative cut-off density layer with a high time resolution. The first results are presented and discussed in this paper. In particular, a relation between edge density and local magnetic topology is proposed as well as a systematic study of the average behaviour over several global operative conditions of the machine. An outlook on the future diagnostic developments is also given.

Published
2011

20. Bifurcation to 3D Helical Magnetic Equilibrium in an Axisymmetric Toroidal Device

Author

W. X. Ding, J. S. Sarff, L. Lin, Fulvio Auriemma, B. E. Chapman, Rita Lorenzini, Emilio Martines, B. Momo, D. L. Brower, P. Zanca, David Terranova, P. Innocente, W. F. Bergerson, Bergerson, W, Auriemma, F, Chapman, B, Ding, W, Zanca, P, Brower, D, Innocente, P, Lin, L, Lorenzini, R, Martines, E, Momo, B, Sarff, J, and Terranova, D

Subjects
Tokamak, Rotational symmetry, General Physics and Astronomy, reversed field pinch, law.invention, symbols.namesake, Helical equilibria, law, Physics::Plasma Physics, Faraday effect, Direct measurement, RFP, QSH, Magnetohydrodynamic drive, TORUS, Physics, Toroid, Mechanics, Magnetic field, quasi-single helicity, Classical mechanics, REVERSED-FIELD PINCH, bifurcation, Pinch, symbols, Axisymmetric, Plasma containment
Abstract

We report the first direct measurement of the internal magnetic field structure associated with a 3D helical equilibrium generated spontaneously in the core of an axisymmetric, magnetically-confined, toroidal plasma. Magnetohydrodynamic equilibrium bifurcation occurs in MST RFP plasmas when the innermost resonant magnetic perturbation grows to large amplitude, reaching up to 8{\%} of the mean field strength. Evolution of the magnetic topology is determined by measuring the Faraday effect, revealing that as the perturbation grows, toroidal symmetry is broken, and a helical equilibrium is established. Computational reconstruction of the magnetic field and electron density profiles based on a 3D topology agrees well with experimental data, providing a better fit than reconstructions based on a standard 2D cylindrical topology. These helical plasmas sometimes exhibit an improvement in electron particle confinement and increased temperature.

Published
2011

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

Author

R. Piovan, A. Fassina, Stefano Munaretto, M. Baruzzo, D. Bonfiglio, E. Gaio, F. Bonomo, D. Lòpez-Bruna, R. Delogu, S. Dal Bello, A. W. Cooper, G. Marchiori, P. Innocente, M. Brombin, G. Serianni, E. Gazza, A. Ferro, S. Martini, R. Paccagnella, A. Alfier, A. Zamengo, A. Canton, Emilio Martines, I. Predebon, A. Soppelsa, B. Momo, M. Zuin, P. Martin, F. Sattin, N. Vianello, L. Apolloni, R. Lorenzini, P. Zanca, M. Agostini, R. Cavazzana, P. Franz, C. Taliercio, G. V. Pereverzev, M. Recchia, Fulvio Auriemma, R. Sanchez, S. C. Guo, D. Terranova, L. Novello, Gianluca Spizzo, M. E. Puiatti, Sheena Menmuir, L. Giudicotti, B. Zaniol, L. Piron, Michael Drevlak, L. Marrelli, Neil Pomphrey, L. Grando, Zhirui Wang, S. Cappello, Gabriele Manduchi, M. Valisa, Roberto Pasqualotto, L. Carraro, G. De Masi, L. Zanotto, S. P. Hirshman, M. Spolaore, S. Spagnolo, P. Scarin, P. Piovesan, T. Bolzonella, M. Gobbin, Allen H. Boozer, Terranova, D, Bonfiglio, D, Boozer, A, Cooper, A, Gobbin, M, Hirshman, S, Lorenzini, R, Marrelli, L, Martines, E, Momo, B, Pomphrey, N, Predebon, I, Sanchez, R, Spizzo, G, Agostini, M, Alfier, A, Apolloni, L, Auriemma, F, Baruzzo, M, Bolzonella, T, Bonomo, F, Brombin, M, Canton, A, Cappello, S, Carraro, L, Cavazzana, R, Dal Bello, S, Delogu, R, De Masi, G, Drevlak, M, Fassina, A, Ferro, A, Franz, P, Gaio, E, Gazza, E, Giudicotti, L, Grando, L, Guo, S, Innocente, P, Lopez-Bruna, D, Manduchi, G, Marchiori, G, Martin, P, Martini, S, Menmuir, S, Munaretto, S, Novello, L, Paccagnella, R, Pasqualotto, R, Pereverzev, G, Piovan, R, Piovesan, P, Piron, L, Puiatti, M, Recchia, M, Sattin, F, Scarin, P, Serianni, G, Soppelsa, A, Spagnolo, S, Spolaore, M, Taliercio, C, Valisa, M, Vianello, N, Wang, Z, Zamengo, A, Zaniol, B, Zanotto, L, Zanca, P, and Zuin, M

Subjects
Tokamak, RFX-mod, CONFINEMENT, reversed field pinch, law.invention, law, Physics::Plasma Physics, RFP, QSH, Statistical physics, Physics, Reversed field pinch, Magnetic confinement fusion, Mechanics, Plasma, Fusion power, Condensed Matter Physics, EVOLUTION, quasi-single helicity, Nuclear Energy and Engineering, REVERSED-FIELD PINCH, Magnetohydrodynamics, TOROIDAL PLASMAS, Plasma stability, Stellarator, COEFFICIENTS
Abstract

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 viewtheVMECcode proved to be an effectiveway 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. © 2010 IOP Publishing Ltd.

Published
2010

22. Helical equilibria and magnetic structures in the reversed field pinch and analogies to the tokamak and stellarator

Author

Stefano Munaretto, L. Carraro, Alessandra Canton, S. Dal Bello, Matteo Zuin, A. Pizzimenti, D. Bonfiglio, S. Martini, V. Antoni, Elena Gaio, Fulvio Auriemma, Lionello Marrelli, Fabio Sattin, B. Momo, Tommaso Bolzonella, Nicola Vianello, L. Apolloni, Emilio Martines, Gianluca Spizzo, M. Baruzzo, R. Delogu, Paolo Franz, Susanna Cappello, P. Piovesan, Italo Predebon, M. Moresco, Rita Lorenzini, Leonardo Giudicotti, L. Novello, Sheena Menmuir, Paolo Scarin, P. Zanca, Anton Soppelsa, Luca Grando, G. De Masi, M. Spolaore, Giuseppe Marchiori, Roberto Pasqualotto, Neil Pomphrey, S. C. Guo, David Terranova, A. Zamengo, P. Innocente, Maria Ester Puiatti, Piero Martin, E. Gazza, Dominique Escande, Alberto Alfier, Allen H. Boozer, M. Valisa, L. Piron, Matteo Agostini, Barbara Zaniol, M. Brombin, R. Piovan, L. Zanotto, E. Spada, Gabriele Manduchi, Gianluigi Serianni, Alessandro Fassina, Roberto Paccagnella, Federica Bonomo, R. Cavazzana, Silvia Spagnolo, Cesare Taliercio, M. Gobbin, Puiatti, M, Alfier, A, Auriemma, F, Cappello, S, Carraro, L, Cavazzana, R, Dal Bello, S, Fassina, A, Escande, D, Franz, P, Gobbin, M, Innocente, P, Lorenzini, R, Marrelli, L, Martin, P, Piovesan, P, Predebon, I, Sattin, F, Spizzo, G, Terranova, D, Valisa, M, Zaniol, B, Zanotto, L, Zuin, M, Agostini, M, Antoni, V, Apolloni, L, Baruzzo, M, Bolzonella, T, Bonfiglio, D, Bonomo, F, Boozer, A, Brombin, M, Canton, A, Delogu, R, De Masi, G, Gaio, E, Gazza, E, Giudicotti, L, Grando, L, Guo, S, Manduchi, G, Marchiori, G, Martines, E, Martini, S, Menmuir, S, Momo, B, Moresco, M, Munaretto, S, Novello, L, Paccagnella, R, Pasqualotto, R, Piovan, R, Piron, L, Pizzimenti, A, Pomphrey, N, Scarin, P, Serianni, G, Spada, E, Soppelsa, A, Spagnolo, S, Spolaore, M, Taliercio, C, Vianello, N, Zamengo, A, and Zanca, P

Subjects
Physics, Tokamak, RFX-mod, Reversed field pinch, Field (physics), Condensed matter physics, Magnetic confinement fusion, reversed field pinch, Edge (geometry), SELF-ORGANIZATION, Condensed Matter Physics, law.invention, Core (optical fiber), quasi-single helicity, INTERNAL TRANSPORT BARRIERS, MHD ACTIVE CONTROL, Nuclear Energy and Engineering, law, RFP, QSH, plasma equilibrium, Atomic physics, Pressure gradient, Stellarator
Abstract

The reversed field pinch configuration is characterized by the presence of magnetic structures both in the core and at the edge: in the core, at high plasma current the spontaneous development of a helical structure is accompanied by the appearance of internal electron transport barriers; at the edge strong pressure gradients, identifying an edge transport barrier, are observed too, related to the position of the field reversal surface. The aim of this paper is the experimental characterization of both the internal and edge transport barriers in relation to the magnetic topology, discussing possible analogies and differences with other confinement schemes. © 2009 IOP Publishing Ltd.

Published
2009

23. Overview of the RFX-mod fusion science programme

Author

Piergiorgio Sonato, S. Dal Bello, Maria Ester Puiatti, Piero Martin, A. Fiorentin, Stefano Munaretto, F. Fellin, G. De Masi, M. Gobbin, Silvia Spagnolo, M. Furno Palumbo, P. Zaccaria, E. Gazza, M. Recchia, Raul Sanchez, Karsten McCollam, G. L. Trevisan, E. Spada, Alessandra Canton, Matteo Zuin, Ivo Furno, Christian Theiler, A. Zamengo, J.Q. Dong, Emilio Martines, B. E. Chapman, M. Dalla Palma, Paolo Franz, M. Brombin, V. Rigato, J. Framarin, Antonio Barbalace, P. Piovesan, Nicola Pilan, Donald A. Spong, Roberto Paccagnella, Wolf-Dieter Schneider, Barbara Zaniol, Fabio Villone, Leonardo Giudicotti, M. De Muri, T.C. Luce, R. Piovan, A. Ruzzon, V. Antoni, Giuseppe Zollino, Emanuele Sartori, Yueqiang Liu, G. Rostagni, M. Baruzzo, Manabu Takechi, Yongkyoon In, R. Delogu, Fulvio Auriemma, J. A. Alonso, M. Barp, C. Piron, D. Bonfiglio, Go Matsunaga, Enrico Zilli, G. Ciaccio, S. Martini, L. Piron, Marco Barbisan, Songfen Liu, M. Veranda, A. Scaggion, Giuseppe Chitarin, N. Pomaro, Luis Chacon, James D. Hanson, L. Apolloni, Yoichi Hirano, M. Spolaore, Francesco Gnesotto, F. Avino, Nicolò Marconato, M. Valente, Alberto Ferro, Fabio Sattin, Pierluigi Veltri, Gabriele Manduchi, L. Zanotto, C. Hidalgo, Paolo Innocente, Simona Barison, L. Novello, Italo Predebon, Rita Lorenzini, David Terranova, Luca Grando, Zhirui Wang, Vanni Toigo, M. Boldrin, M. Bigi, Adriano Luchetta, Paolo Bettini, Erik Olofsson, Andrea Rizzolo, Gianluigi Serianni, Anton Soppelsa, Cesare Taliercio, Roscoe White, C. Finotti, Susanna Cappello, N. Fonnesu, Roberto Pasqualotto, Paolo Scarin, R. Bilel, Shunsuke Ide, Alessandro Fassina, A. Maistrello, D. Carralero, Matteo Agostini, W. A. Cooper, P. Zanca, A. Buffa, Piero Agostinetti, G. Mazzitelli, X. Y. Xu, S. Fiameni, M. Moresco, John M. Finn, Lionello Marrelli, B. Momo, Tommaso Bolzonella, Nicola Vianello, Giuseppe Marchiori, D.K. Mansfield, M. Valisa, M. Okabayashi, S. C. Guo, Dominique Escande, Lorella Carraro, A. Pesce, M. Pavei, F. Ghezzi, Roberto Cavazzana, Satoru Kiyama, W. A. Gonzales, Simone Peruzzo, S.P. Hirshman, Elena Gaio, T. Barbui, Hajime Sakakita, G.L. Jackson, J. S. Sarff, Ambrogio Fasoli, D. Lopez Bruna, A. L. Roquemore, Federica Bonomo, F. Fantini, Lorenzo Frassinetti, C. Bustreo, Diego Marcuzzi, G. L. Delzanno, Gianluca Spizzo, A. De Lorenzi, Martin, P, Puiatti, M, Agostinetti, P, Agostini, M, Alonso, J, Antoni, V, Apolloni, L, Auriemma, F, Avino, F, Barbalace, A, Barbisan, M, Barbui, T, Barison, S, Barp, M, Baruzzo, M, Bettini, P, Bigi, M, Bilel, R, Boldrin, M, Bolzonella, T, Bonfiglio, D, Bonomo, F, Brombin, M, Buffa, A, Bustreo, C, Canton, A, Cappello, S, Carralero, D, Carraro, L, Cavazzana, R, Chacon, L, Chapman, B, Chitarin, G, Ciaccio, G, Cooper, W, Dal Bello, S, Dalla Palma, M, Delogu, R, De Lorenzi, A, Delzanno, G, De Masi, G, De Muri, M, Dong, J, Escande, D, Fantini, F, Fasoli, A, Fassina, A, Fellin, F, Ferro, A, Fiameni, S, Finn, J, Finotti, C, Fiorentin, A, Fonnesu, N, Framarin, J, Franz, P, Frassinetti, L, Furno, I, Palumbo, M, Gaio, E, Gazza, E, Ghezzi, F, Giudicotti, L, Gnesotto, F, Gobbin, M, Gonzales, W, Grando, L, Guo, S, Hanson, J, Hidalgo, C, Hirano, Y, Hirshman, S, Ide, S, In, Y, Innocente, P, Jackson, G, Kiyama, S, Liu, S, Liu, Y, Lopez Bruna, D, Lorenzini, R, Luce, T, Luchetta, A, Maistrello, A, Manduchi, G, Mansfield, D, Marchiori, G, Marconato, N, Marcuzzi, D, Marrelli, L, Martini, S, Matsunaga, G, Martines, E, Mazzitelli, G, Mccollam, K, Momo, B, Moresco, M, Munaretto, S, Novello, L, Okabayashi, M, Olofsson, E, Paccagnella, R, Pasqualotto, R, Pavei, M, Peruzzo, S, Pesce, A, Pilan, N, Piovan, R, Piovesan, P, Piron, C, Piron, L, Pomaro, N, Predebon, I, Recchia, M, Rigato, V, Rizzolo, A, Roquemore, A, Rostagni, G, Ruzzon, A, Sakakita, H, Sanchez, R, Sarff, J, Sartori, E, Sattin, F, Scaggion, A, Scarin, P, Schneider, W, Serianni, G, Sonato, P, Spada, E, Soppelsa, A, Spagnolo, S, Spolaore, M, Spong, D, Spizzo, G, Takechi, M, Taliercio, C, Terranova, D, Theiler, C, Toigo, V, Trevisan, G, Valente, M, Valisa, M, Veltri, P, Veranda, M, Vianello, N, Villone, F, Wang, Z, White, R, Xu, X, Zaccaria, P, Zamengo, A, Zanca, P, Zaniol, B, Zanotto, L, Zilli, E, Zollino, G, Zuin, M, and Mazzitelli, G.

Subjects
Nuclear and High Energy Physics, RFX-mod, Tokamak, Strong interaction, reversed field pinch, law.invention, Magnetohydrodynamics, law, RFP, Fusion, Safety factor, Reversed field pinch, Flow transport, Settore FIS/01 - Fisica Sperimentale, Iter tokamak, Fusion power, IAEA Fusion Energy Conference, Science and Technology, Condensed Matter Physics, Active control, Plasma parameter, Plasma devices, Systems engineering, Fusion devices, Magnetic configuration, Stellarator
Abstract

This paper reports the highlights of the RFX-mod fusion science programme since the last 2010 IAEA Fusion Energy Conference. The RFX-mod fusion science programme focused on two main goals: exploring the fusion potential of the reversed field pinch (RFP) magnetic configuration and contributing to the solution of key science and technology problems in the roadmap to ITER. Active control of several plasma parameters has been a key tool in this endeavour. New upgrades on the system for active control of magnetohydrodynamic (MHD) stability are underway and will be presented in this paper. Unique among the existing fusion devices, RFX-mod has been operated both as an RFP and as a tokamak. The latter operation has allowed the exploration of edge safety factor q edge < 2 with active control of MHD stability and studies concerning basic energy and flow transport mechanisms. Strong interaction has continued with the stellarator community in particular on the physics of helical states and on three-dimensional codes. © 2013 IAEA, Vienna.

Published
2013

24. Overview of the RFX-mod contribution to the international Fusion Science Program

Author

M. Pavei, Alessandra Canton, Matteo Agostini, R. Piovan, Matteo Zuin, G. Mazzitelli, L. Piron, N. Vianello, J.Q. Dong, B. E. Chapman, A. Zamengo, Gianluca Spizzo, Paolo Zanca, T. Barbui, Hajime Sakakita, Piergiorgio Sonato, Nicola Pilan, Yueqiang Liu, Daniele Bonfiglio, P. Piovesan, Lorella Carraro, T.C. Luce, J. L. Jackson, C. Finotti, E. Miorin, M. Recchia, S.P. Hirshman, Rita Lorenzini, Andrea Rizzolo, Roberto Paccagnella, G. Ciaccio, A. Scaggion, Enrico Zilli, Nicolò Marconato, Paolo Scarin, S. Martini, M. Baruzzo, James D. Hanson, M. Veranda, L. Marrelli, M. Bigi, Marco Barbisan, W. A. Cooper, L. Zanotto, Piero Agostinetti, L. Laguardia, Chenguang Li, C. Taliercio, F. Fellin, Oliver Schmitz, Cristian Ruset, Luca Grando, Zhirui Wang, Lorenzo Frassinetti, Silvia Spagnolo, X. Y. Xu, Simone Peruzzo, B. Esposito, Erik Olofsson, Elena Gaio, M. Furno Palumbo, M. Okabayashi, Nisarg Patel, G. L. Trevisan, Matthias Komm, M. Spolaore, Francesco Gnesotto, S. C. Guo, Raul Sanchez, D. Terranova, Susanna Cappello, R. Bilel, G. Urso, Marco Gobbin, Fabio Villone, E. Spada, M. Moresco, D. Cester, Emanuele Sartori, L. Pigatto, Leonardo Giudicotti, B. Momo, Tommaso Bolzonella, Piero Martin, Luis Chacon, A. L. Roquemore, F. Belli, Barbara Zaniol, C. Piron, F. Sattin, N. Visona, F. Ghezzi, R. Delogu, Emilio Martines, Diego Marcuzzi, D. F. Escande, A. De Lorenzi, M. Dalla Palma, Paolo Franz, Cristina Rea, Adriano Luchetta, Paolo Bettini, Roscoe White, A. Maistrello, Alessandro Fassina, G. Rostagni, Manabu Takechi, Roberto Cavazzana, G. Viesti, M. Boldrin, V. Yanovskiy, Giuseppe Marchiori, D.K. Mansfield, Satoru Kiyama, W. A. Gonzales, M. Valisa, A. Buffa, Pavlos Xanthopoulos, J. S. Sarff, M. E. Puiatti, Go Matsunaga, M. Valente, S. M. Deambrosis, Alberto Ferro, Paolo Innocente, Italo Predebon, V. Rigato, S. Dal Bello, Gabriele Manduchi, Fulvio Auriemma, G. De Masi, P. Vincenzi, Donald A. Spong, M. Battistella, Songfen Liu, D. Marocco, M. Brombin, Laszlo Sajo-Bohus, Giuseppe Chitarin, A. Ruzzon, V. Antoni, L. Stevanato, Consorzio RFX, Associazione Euratom/ENEA sulla Fusione (RFX), Agenzia Nazionale per le nuove Tecnologie, l’energia e lo sviluppo economico sostenibile = Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Laboratori Nazionali di Frascati (LNF), Istituto Nazionale di Fisica Nucleare (INFN), National Institute for Laser, Plasma and Radiation Physics (INFLPR), STMicroelectronics [Crolles] (ST-CROLLES), Canadian Institute for Theoretical Astrophysics (CITA), Département Méthodes et Modèles Mathématiques pour l'Industrie (3MI-ENSMSE), École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Centre G2I, Physique des interactions ioniques et moléculaires (PIIM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Department of Physics [Stockholm], Stockholm University, Inst Subtrop Agr, Res Ctr Healthy Breeding Livestock & Poultry, Hunan Engn, Chinese Academy of Sciences [Changchun Branch] (CAS), Inst Subtrop Agr, Res Ctr Anim & Poultry Sci, Inst Subtrop Agr, Key Lab Agroecol Proc Subtrop Reg, Puiatti, M, Dal Bello, S, Marrelli, L, Martin, P, Agostinetti, P, Agostini, M, Antoni, V, Auriemma, F, Barbisan, M, Barbui, T, Baruzzo, M, Battistella, M, Belli, F, Bettini, P, Bigi, M, Bilel, R, Boldrin, M, Bolzonella, T, Bonfiglio, D, Brombin, M, Buffa, A, Canton, A, Cappello, S, Carraro, L, Cavazzana, R, Cester, D, Chacon, L, Chapman, B, Chitarin, G, Ciaccio, G, Cooper, W, Dalla Palma, M, Deambrosis, S, Delogu, R, De Lorenzi, A, De Masi, G, Dong, J, Escande, D, Esposito, B, Fassina, A, Fellin, F, Ferro, A, Finotti, C, Franz, P, Frassinetti, L, Palumbo, M, Gaio, E, Ghezzi, F, Giudicotti, L, Gnesotto, F, Gobbin, M, Gonzales, W, Grando, L, Guo, S, Hanson, J, Hirshman, S, Innocente, P, Jackson, J, Kiyama, S, Komm, M, Laguardia, L, Li, C, Liu, S, Liu, Y, Lorenzini, R, Luce, T, Luchetta, A, Maistrello, A, Manduchi, G, Mansfield, D, Marchiori, G, Marconato, N, Marocco, D, Marcuzzi, D, Martines, E, Martini, S, Matsunaga, G, Mazzitelli, G, Miorin, E, Momo, B, Moresco, M, Okabayashi, M, Olofsson, E, Paccagnella, R, Patel, N, Pavei, M, Peruzzo, S, Pilan, N, Pigatto, L, Piovan, R, Piovesan, P, Piron, C, Piron, L, Predebon, I, Rea, C, Recchia, M, Rigato, V, Rizzolo, A, Roquemore, A, Rostagni, G, Ruset, C, Ruzzon, A, Sajo-Bohus, L, Sakakita, H, Sanchez, R, Sarff, J, Sartori, E, Sattin, F, Scaggion, A, Scarin, P, Schmitz, O, Sonato, P, Spada, E, Spagnolo, S, Spolaore, M, Spong, D, Spizzo, G, Stevanato, L, Takechi, M, Taliercio, C, Terranova, D, Trevisan, G, Urso, G, Valente, M, Valisa, M, Veranda, M, Vianello, N, Viesti, G, Villone, F, Vincenzi, P, Visona', N, Wang, Z, White, R, Xanthopoulos, P, Xu, X, Yanovskiy, V, Zamengo, A, Zanca, P, Zaniol, B, Zanotto, L, Zilli, E, Zuin, M, and Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA)

Subjects
Convection, Physics, [PHYS]Physics [physics], Nuclear and High Energy Physics, Toroid, Tokamak, Reversed field pinch, Turbulence, single helicity, Electron, Mechanics, Sawtooth wave, reversed field pinch, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, 3D boundary, law, Physics::Plasma Physics, 0103 physical sciences, Magnetohydrodynamics, Atomic physics, 010306 general physics, tokamak
Abstract

25th Fusion Energy Conference (FEC), Govt Russian Federat, St ă Petersburg, RUSSIA, OCT 13-18, 2014; International audience; The RFX-mod device is operated both as a reversed field pinch (RFP), ă where advanced regimes featuring helical shape develop, and as a ă tokamak. Due to its flexibility, RFX-mod is contributing to the solution ă of key issues in the roadmap to ITER and DEMO, including MHD instability ă control, internal transport barriers, edge transport and turbulence, ă isotopic effect, high density limit and three-dimensional (3D) ă non-linear MHD modelling. This paper reports recent advancements in the ă understanding of the self-organized helical states, featuring a strong ă electron transport barrier, in the RFP configuration; the physical ă mechanism driving the residual transport at the barrier has been ă investigated. Following the first experiments with deuterium as the ă filling gas, new results concerning the isotope effect in the RFP are ă discussed. Studies on the high density limit show that in the RFP it is ă related to a toroidal particle accumulation due to the onset of a ă convective cell. In the tokamak configuration, q(a) regimes down to q(a) ă = 1.2 have been pioneered, with (2,1) tearing mode (TM) mitigated and ă (2,1) resistive wall mode (RWM) stabilized: the control of such modes ă can be obtained both by poloidal and radial sensors. Progress has been ă made in the avoidance of disruptions due to the (2,1) TM by applying ă q(a) control, and on the general issue of error field control. The ă effect of externally applied 3D fields on plasma flow and edge ă turbulence, sawtooth control and runaway electron decorrelation has been ă analysed. The experimental program is supported by substantial ă theoretical activity: 3D non-linear visco-resistive MHD and non-local ă transport modelling have been advanced; RWMs have been studied by a ă toroidal MHD kinetic hybrid stability code.

25. Comparative studies of electrostatic turbulence induced transport in presence of resonant magnetic perturbations in RFX-mod

Author

Cristina Rea, Monica Spolaore, Gianluca Spizzo, Roberto Cavazzana, Matteo Agostini, M. Zuin, Silvia Spagnolo, P. Scarin, N. Vianello, G. De Masi, B. Momo, Emilio Martines, Rea, C, Vianello, N, Agostini, M, Cavazzana, R, De Masi, G, Martines, E, Momo, B, Scarin, P, Spagnolo, S, Spizzo, G, Spolaore, M, and Zuin, M

Subjects
Nuclear and High Energy Physics, Tokamak, Field line, 01 natural sciences, Resonant magnetic perturbations, 010305 fluids & plasmas, law.invention, law, Physics::Plasma Physics, 0103 physical sciences, plasma physic, RFP, Wavenumber, 010306 general physics, tokamak, RMPs, Physics, Reversed field pinch, plasma physics, plasma edge, RMP, Plasma, Condensed Matter Physics, Computational physics, Magnetic field, transport, Pinch, Atomic physics, electrostatic turbulence
Abstract

Three-dimensional non-axisymmetric magnetic fields are purposely applied to toroidally symmetric fusion plasmas in order to modify transport of heat and particle fluxes to the plasma-facing components (PFCs), and specifically to control and suppress edge localized modes (ELMs) in H-mode tokamak plasmas. This paper presents a comparative study between two magnetic configurations available in the RFX-mod device, namely the original reversed-field pinch configuration and the more recent low-field circular ohmic tokamak. The paper presents a detailed analysis of the modulation of electrostatic turbulence and induced transport in the presence of an externally applied magnetic perturbation, as measured in both configurations. A detailed study of the underlying magnetic topology in both configurations is given through the field line tracing code FLiT. The electrostatic turbulence induced flux is observed to be modulated by the underlying topology, with an enhancement close to the O-point and a reduction at the X-point of the induced magnetic island. The transport modification are discussed in terms of relevant frequency and wavenumber spectrum.

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