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11 results on '"Veranda, M."'

1. Modeling of Basic Physics Issues in Toroidal Pinches and Tools for Performance Control

Author

Cappello S., Bonfiglio D., Di Giannatale G., Escande D., Kryzhanovskyy A., Manduchi G., Rigoni A., Sattin F., Spinicci L., Spizzo G., Veranda M., Vivenzi N., Chacon L., Grasso D., Falessi M.V., and Pegoraro F.

Subjects
Basic Physics Issues, Physics::Plasma Physics, Tokamak, Performance Control, Reversed Field Pink, Toroidal Pinches
Abstract

Recent progress about helical self-organization studies is reported. Extensive exploita5on of 3D nonlinear visco-resistive modeling, SpeCyl code, which describes current-driven dynamics typical of pinch configura5ons in cylindrical geometry. Magnetic topology studies are based on the Field Line Tracing code NEMATO and a new refined tool to detect Lagrangian Coherent Structures is compared with results from a temperature equa/on solver. The following Physics Issues in helical self-organization are addressed: o Boundary Conditions and dimensionless parameters impact, (RFP, and circular Tokamak) o Forma5on of internal transport barriers, (RFP) o Temporary loss of opera5onal point, reconnec5on events, (RFP and circular Tokamak), o Alfvén waves excitation (RFP and circular Tokamak), RESULTS show: o Reasonable comparison (validation) with RFP experimental observations, o Similarities between RFP and Tokamak-like configuration.

Published
2021

2. 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

3. HELICAL MAGNETIC SELF-ORGANIZATION OF PLASMAS IN TOROIDAL PINCHES WITH TRANSPORT BARRIER FORMATION

Author

Veranda M., Bonfiglio D., Cappello S., Chacon L., Escande D.E., and di Giannatale G.

Subjects
RFX-Mod, Physics::Plasma Physics, MHD, toroidal pinch configurations, helical magnetic self-organization, reversed-field pinch, plasmas, toroidal pinches, tokamak
Abstract

Nonlinear MHD modeling of toroidal pinch configurations (reversed-field pinch and tokamak) for hot plasma confinement describes several features of the helical self-organization, observed in both reversed-field pinches and tokamaks. It can also give a hint on why transport barriers are formed, by far one of the more interesting observations in experiments. The research work will be summarized in two points. The first one regards the recent successful technique to "channel" reversed-field pinches into a chosen macroscopic helical shape through the use of small edge magnetic perturbations. Helical self-organization is predicted in nonlinear MHD modeling, successfully tested in RFX-mod experiment in Padova and awaits further exploration in the updated device RFX-mod2. The upgraded machine, soon starting operation, is characterized by a shell-plasma proximity reduction, likely improving feedback coils action, thus favoring the study of the beneficial properties of helical states built upon helixes not resonating with the safety factor profile. The second point regards the MHD description of the process of formation of transport barriers by macroscopic magnetic chaos healing, which allows the emergence of hidden Lagrangian structures acting as barriers to the transport. The radial position of such structures is observed to correspond to higher gradients of magnetic field lines connection length to the edge and to higher temperature gradients, computed by numerically solving the anisotropic heat flow equation. Comparison with thermal measurements in RFX-mod will also be offered.

Published
2019

4. Connections between RFP, Tokamak and Stellarator physics as highlighted in 3D nonlinear MHD modelling

Author

Bonfiglio D., Cappello S., Escande D.F., Veranda M., Borgogno D., Chacon L., Grasso D., and Rubino G.

Subjects
MHD modelling, Physics::Plasma Physics, Tokamak, RFP, Reversed Field Pinch, 3D nonlinear, Stellarator
Abstract

The understanding of fusion plasmas benefits from investigating the same phenomena in different magnetic configurations such as the tokamak, the stellarator, and the reversed - field pinch (RFP) [1 - 4] . Here, the same approach is applied i n the framework of nonlinear 3D MHD modelling . We first focus on sawtoothing, i.e. , the quasiperiodic magnetic relaxation of RFP and tokamak plasma s . Sawtooth ing manifests itself together with magnetic reconnection events , and with the formation of current sheets and of dynamo electric fields . Such processes are relevant to laboratory and astrophysical plasmas as well. In both tokamak and RFP configurations , sawtoothing is quenched leading to long - l a sting helical states whenever visco - resistive dissipation is increased [ 5 ,6 ] or small helical mag netic perturbations (MPs) are applied [ 7 ,8 ]. A similar effect of MPs has been observed in the RFX - mod device [ 9 ]. We secondly consider the topological properties of partially ergodic magnetic field s , which characterize helical states in the RFP [7] . Barriers to the stochastic diffusion of field lines (the so - called cantori also studied in the tokamak configuration [10] ) are diagnosed in the weakly stochastic core of the helical RFP [ 1 1 ] , which could explain experimentally observed internal transport barriers. C hains of magnetic island s naturally occur at the RFP edge [1 2 ] . Such chains may be exploited to realize a so - called island divertor, which may alleviate plasma - wall interaction s like in the stellarator [3]. Numerical results are provided by two MHD codes , successfully benc hmarked against one another [ 6 ].

Published
2016

5. 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

6. 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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7. 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

8. 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

9. 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

10. 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

11. 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.

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