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552 results on '"White, R. B."'

1. Shifting and splitting of resonance lines due to dynamical friction in plasmas

Author

Duarte, V. N., Lestz, J. B., Gorelenkov, N. N., and White, R. B.

Subjects
Physics - Plasma Physics
Abstract

A quasilinear plasma transport theory that incorporates Fokker-Planck dynamical friction (drag) and pitch angle scattering is self-consistently derived from first principles for an isolated, marginally-unstable mode resonating with an energetic minority species. It is found that drag fundamentally changes the structure of the wave-particle resonance, breaking its symmetry and leading to the shifting and splitting of resonance lines. In contrast, scattering broadens the resonance in a symmetric fashion. Comparison with fully nonlinear simulations shows that the proposed quasilinear system preserves the exact instability saturation amplitude and the corresponding particle redistribution of the fully nonlinear theory. Even in situations in which drag leads to a relatively small resonance shift, it still underpins major changes in the redistribution of resonant particles. This novel influence of drag is equally important in plasmas and gravitational systems. In fusion plasmas, the effects are especially pronounced for fast-ion-driven instabilities in tokamaks with low aspect ratio or negative triangularity, as evidenced by past observations. The same theory directly maps to the resonant dynamics of the rotating galactic bar and massive bodies in its orbit, providing new techniques for analyzing galactic dynamics., Comment: Accepted for publication in Physical Review Letters

Published
2020

2. Resonance frequency broadening of wave-particle interaction in tokamaks due to Alfv\'{e}nic eigenmode

Author

Meng, G., Gorelenkov, N. N., Duarte, V. N., Berk, H. L., White, R. B., Bhattacharjee, A., and Wang, X. G.

Subjects
Physics - Plasma Physics
Abstract

We use a guiding center code ORBIT to study the broadening of resonances and the parametric dependence of the resonance frequency broadening width $\Delta\Omega$ on the nonlinear particle trapping frequency $\omega_b$ of wave-particle interaction with specific examples using realistic equilibrium DIII-D shot 159243 (Collins et al. 2016 Phys. Rev. Lett. 116 095001). When the mode amplitude is small, the pendulum approximation for energetic particle dynamics near the resonance is found to be applicable and the ratio of the resonance frequency width to the deeply trapped bounce frequency $\Delta\Omega/\omega_b$ equals 4, as predicted by theory. This factor 4 is demonstrated for the first time in realistic instability conditions. It is found that as the mode amplitude increases, the coefficient $a=\Delta\Omega/\omega_b$ becomes increasingly smaller because of the breaking down of the nonlinear pendulum approximation for the wave-particle interaction., Comment: 27 pages, 14 figures, 15th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems (Princeton, NJ, USA, 2017)

Published
2017
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3. Bound State Energies using Phase Integral Analysis

Author

White, R. B. and Kutlin, A. G.

Subjects
Quantum Physics
Abstract

The study of asymptotic properties of solutions to differential equations has a long and arduous history, with the most significant advances having been made in the development of quantum mechanics. A very powerful method of analysis is that of Phase Integrals, described by Heading. Key to this analysis are the Stokes constants and the rules for analytic continuation of an asymptotic solution through the complex plane. These constants are easily determined for isolated singular points, by analytically continuing around them and, in the case of analytic functions, requiring the asymptotic solution to be single valued. However, most interesting problems of mathematical physics involve several singular points. By examination of analytically tractable problems and more complex bound state problems involving multiple singular points, we show that the method of Phase Integrals can greatly improve the determination of bound state energies over the simple WKB values. We also find from these examples that in the limit of large separation the Stokes constant for a first order singular point approaches the isolated singular point value., Comment: 19 pages

Published
2017

5. Energetic particle instabilities in fusion plasmas

Author

Sharapov, S E, Alper, B, Berk, H L, Borba, D N, Breizman, B N, Challis, C D, Classen, I G J, Edlund, E M, Eriksson, J, Fasoli, A, Fredrickson, E D, Fu, G Y, Garcia-Munoz, M, Gassner, T, Ghantous, K, Goloborodko, V, Gorelenkov, N N, Gryaznevich, M P, Hacquin, S, Heidbrink, W W, Hellesen, C, Kiptily, V G, Kramer, G J, Lauber, P, Lilley, M K, Lisak, M, Nabais, F, Nazikian, R, Nyqvist, R, Osakabe, M, von Thun, C Perez, Pinches, S D, Podesta, M, Porkolab, M, Shinohara, K, Schoepf, K, Todo, Y, Toi, K, Van Zeeland, M A, Voitsekhovich, I, White, R B, Yavorskij, V, TG, ITPA EP, and Contributors, JET-EFDA

Subjects
Physics - Plasma Physics
Abstract

Remarkable progress has been made in diagnosing energetic particle instabilities on present-day machines and in establishing a theoretical framework for describing them. This overview describes the much improved diagnostics of Alfven instabilities and modelling tools developed world-wide, and discusses progress in interpreting the observed phenomena. A multi-machine comparison is presented giving information on the performance of both diagnostics and modelling tools for different plasma conditions outlining expectations for ITER based on our present knowledge., Comment: 37 pages, 20 figures

Published
2013
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10. Development of a reduced model for energetic particle transport by sawteeth in tokamaks

Author

Podesta, M., Gorelenkova, M., Gorelenkov, N. N., White, R. B., Bonofiglo, P. J., Poli, F. M., Teplukhina, A., Yang, J., Cecconello, Marco, Vallar, M., Podesta, M., Gorelenkova, M., Gorelenkov, N. N., White, R. B., Bonofiglo, P. J., Poli, F. M., Teplukhina, A., Yang, J., Cecconello, Marco, and Vallar, M.

Abstract

The sawtooth instability is known for inducing transport and loss of energetic particles (EPs), and for generating seed magnetic islands that can trigger tearing modes. Both effects degrade the overall plasma performance. Several theories and numerical models have been previously developed to quantify the expected EP transport caused by sawteeth, with various degrees of sophistication to differentiate the response of EPs at different energies and on different orbits (e.g. passing vs. trapped), although the analysis is frequently limited to a single time slice during a tokamak discharge. This work describes the development and initial benchmark of a framework that enables a reduced model for EP transport by sawteeth retaining the full EP phase-space information. The model, implemented in the ORBIT hamiltonian particle-following code, can be used either as a standalone post-processor taking input data from codes such as TRANSP, or as a pre-processor to compute transport coefficients that can be fed back to TRANSP for time-dependent simulations including the effects of sawteeth on EPs. The advantage of the latter approach is that the evolution of the EP distribution can be simulated quantitatively for sawtoothing discharges, thus enabling a more accurate modeling of sources, sinks and overall transport properties of EP and thermal plasma species for comprehensive physics studies that require detailed information of the fast-ion distribution function and its evolution over time.

Published
2022
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11. Nonuniversality of transport for the standard map

Author

Kassibrakis, S., Benkadda, S., White, R. B., Zaslavsky, G. M., Araki, H., editor, Beig, R., editor, Ehlers, J., editor, Frisch, U., editor, Hepp, K., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Benkadda, Sadruddin, editor, and Zaslavsky, George M., editor

Published
1998
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14. Collisionless losses of fast ions in the divertor tokamak test due to toroidal field ripple

Author

Spizzo, G., Gobbin, M., Agostinetti, P., Albanese, R., Ambrosino, R., Casiraghi, I., Cecconello, Marco, Falessi, M. V., Granucci, G., Mantica, P., Martin, P., Vallar, M., Vincenzi, P., Vlad, G., White, R. B., Zonca, F., Spizzo, G., Gobbin, M., Agostinetti, P., Albanese, R., Ambrosino, R., Casiraghi, I., Cecconello, Marco, Falessi, M. V., Granucci, G., Mantica, P., Martin, P., Vallar, M., Vincenzi, P., Vlad, G., White, R. B., and Zonca, F.

Abstract

In this paper we analyze fast ion motion in the divertor tokamak test (DTT) device (Albanese et al 2017 Nucl. Fusion 57 016010). It is planned that DTT will be heated through a mix of 45 MW heating power, including 15 MW negative-ion-based neutral beam heating (NNBI) which is currently being developed by Consorzio RFX in Padova, Italy (Agostinetti et al 2019 Fusion Eng. Design 146 441-446). An issue for DTT is that a toroidal field (TF) ripple with a maximum value of about similar to 0.42% (with respect to the on-axis magnetic field B (0)) is expected on the low-field side, and this ripple interacts with fast ions through the rather well-known phenomena of ripple-precession resonances, in addition to prompt losses of ions which do not complete a full orbit in the poloidal plane. We will show that, with the planned geometry of NNBI, prompt losses are negligible, and ripple-precession losses amount to a maximum of 0.15%. The calculations are performed with the guiding center code Orbit using two different equilibria, and a beam with an energy of 400 keV and the injection angle alpha (inj) = 40 degrees (measured w.r.t. the first wall), which corresponds to a pitch of injected particles lambda = v (parallel to)/v approximate to sin alpha (inj) = 0.65. The main resonances are of the form omega (b) - nN omega (d) = 0, omega (b) and omega (d) being the bounce and precession frequency, respectively, N = 18 the ripple periodicity and 3 <= n <= 6 are the toroidal wavenumbers of the resonances. Although collisionless interaction with the TF ripple does not pose a serious threat to the NNBI project, an open question remains as to whether the presence of these resonances will interact with fast particles accelerated by Alfven eigenmodes, and if stochastization of the resonances is possible in DTT, as was observed in the past in TORE SUPRA.

Published
2021
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29. Self-organized helical equilibria as a new paradigm for ohmically heated fusion plasmas

Author

Lorenzini, R., Martines, E., Piovesan, P., Terranova, D., Zanca, P., Zuin, M., Alfier, A., Bonfiglio, D., Bonomo, F., Canton, A., Cappello, S., Carraro, L., Cavazzana, R., Escande, D. F., Fassina, A., Franz, P., Gobbin, M., Innocente, P., Marrelli, L., Pasqualotto, R., Puiatti, M. E., Spolaore, M., Valisa, M., Vianello, N., Martin, P., Apolloni, L., Adamek, J., Agostini, M., Annibaldi, S. V., Antoni, V., Auriemma, F., Barana, O., Baruzzo, M., Bettini, P., Bolzonella, T., Brombin, M., Brotankova, J., Buffa, A., Buratti, P., Cavinato, M., Chapman, B. E., Chitarin, G., Bello, S. D., Lorenzi, A. D., Masi, G. D., Ferro, A., Gaio, E., Gazza, E., Giudicotti, L., Gnesotto, F., Grando, L., Guazzotto, L., Guo, S. C., Igochine, V., Liu, Y. Q., Luchetta, A., Manduchi, G., Marchiori, G., Marcuzzi, D., Martini, S., McCollam, K., Milani, F., Moresco, M., Novello, L., Ortolani, S., Paccagnella, R., Peruzzo, S., Piovan, R., Piron, L., Pizzimenti, A., Pomaro, N., Predebon, I., Reusch, J. A., Rostagni, G., Rubinacci, G., Sarff, J. S., Sattin, F., Scarin, P., Serianni, G., Sonato, P., Spada, E., Soppelsa, A., Spagnolo, S., Spizzo, G., Taliercio, C., Toigo, V., Villone, F., White, R. B., Yadikin, D., Zaccaria, P., Zamengo, A., Zaniol, B., Zanotto, L., Zilli, E., Zohm, H., Zuin, M. Z., Lorenzini, R., Martines, E., Piovesan, P., Terranova, D., Zanca, P., Zuin, M., Alfier, A., Bonfiglio, D., Bonomo, F., Canton, A., Cappello, S., Carraro, L., Cavazzana, R., Escande, D. F., Fassina, A., Franz, P., Gobbin, M., Innocente, P., Marrelli, L., Pasqualotto, R., Puiatti, M. E., Spolaore, M., Valisa, M., Vianello, N., Martin, P., Apolloni, L., Adamek, J., Agostini, M., Annibaldi, S. V., Antoni, V., Auriemma, F., Barana, O., Baruzzo, M., Bettini, P., Bolzonella, T., Brombin, M., Brotankova, J., Buffa, A., Buratti, P., Cavinato, M., Chapman, B. E., Chitarin, G., Bello, S. D., Lorenzi, A. D., Masi, G. D., Ferro, A., Gaio, E., Gazza, E., Giudicotti, L., Gnesotto, F., Grando, L., Guazzotto, L., Guo, S. C., Igochine, V., Liu, Y. Q., Luchetta, A., Manduchi, G., Marchiori, G., Marcuzzi, D., Martini, S., Mccollam, K., Milani, F., Moresco, M., Novello, L., Ortolani, S., Paccagnella, R., Peruzzo, S., Piovan, R., Piron, L., Pizzimenti, A., Pomaro, N., Predebon, I., Reusch, J. A., Rostagni, G., Rubinacci, G., Sarff, J. S., Sattin, F., Scarin, P., Serianni, G., Sonato, P., Spada, E., Soppelsa, A., Spagnolo, S., Spizzo, G., Taliercio, C., Toigo, V., Villone, F., White, R. B., Yadikin, D., Zaccaria, P., Zamengo, A., Zaniol, B., Zanotto, L., Zilli, E., Zohm, H., Zuin, M. Z., Lorenzini, R, Martines, E, Piovesan, P, Terranova, D, Zanca, P, Zuin, M, Alfier, A, Bonfiglio, D, Bonomo, F, Canton, A, Cappello, S, Carraro, L, Cavazzana, R, Escande, D, Fassina, A, Franz, P, Gobbin, M, Innocente, P, Marrelli, L, Pasqualotto, R, Puiatti, M, Spolaore, M, Valisa, M, Vianello, N, and Martin, P

Subjects
Physics, quasi-single-helicity, Toroid, Tokamak, Fusion plasma, General Physics and Astronomy, Magnetic confinement fusion, reversed field pinch, Mechanics, Plasma, Fusion power, Instability, law.invention, Physics::Plasma Physics, law, RFP, Pinch, QSH, Atomic physics
Abstract

In the quest for new energy sources, the research on controlled thermonuclear fusion has been boosted by the start of the construction phase of the International Thermonuclear Experimental Reactor (ITER). ITER is based on the tokamak magnetic configuration, which is the best performing one in terms of energy confinement. Alternative concepts are however actively researched, which in the long term could be considered for a second generation of reactors. Here, we show results concerning one of these configurations, the reversed-field pinch (RFP). By increasing the plasma current, a spontaneous transition to a helical equilibrium occurs, with a change of magnetic topology. Partially conserved magnetic flux surfaces emerge within residual magnetic chaos, resulting in the onset of a transport barrier. This is a structural change and sheds new light on the potential of the RFP as the basis for a low-magnetic-field ohmic fusion reactor. © 2009 Macmillan Publishers Limited.

Published
2009

35. Overview of the RFX-mod fusion science activity

Author

Zuin, M., Dal Bello, S., Marrelli, L., Puiatti, M. E., 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. A., Cordaro, L., Palma, M. Dalla, Deambrosis, S., Delogu, R., De Lorenzi, A., De Masi, G., Dong, J. Q., Escande, D. F., Fassina, A., Felici, F., Ferro, A., Finotti, C., Franz, P., Frassinetti, Lorenzo, Gaio, E., Ghezzi, F., Giudicotti, L., Gnesotto, F., Gobbin, M., Gonzalez, W. A., Grando, L., Guo, S. C., Hanson, J. D., Hirshman, S. P., Innocente, P., Jackson, J. L., Kiyama, S., Komm, M., Kudlacek, O., Laguardia, L., Li, C., Liu, B., Liu, S. F., Liu, Y. Q., Lopez-Bruna, D., Lorenzini, R., Luce, T. C., Luchetta, A., Maistrello, A., Manduchi, G., Mansfield, D. K., 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., Sajo-Bohus, L., Sakakita, H., Sanchez, R., Sarff, J. S., Sattin, F., Scarin, P., Schmitz, O., Schneider, W., Siragusa, M., Sonato, P., Spada, E., Spagnolo, S., Spolaore, M., Spong, D. A., 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., Visona, N., White, R. B., Xanthopoulos, P., Xu, X. Y., Yanovskiy, V., Zamengo, A., Zanca, P., Zaniol, B., Zanotto, L., Zhang, Y., Zilli, E., Zuin, M., Dal Bello, S., Marrelli, L., Puiatti, M. E., 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. A., Cordaro, L., Palma, M. Dalla, Deambrosis, S., Delogu, R., De Lorenzi, A., De Masi, G., Dong, J. Q., Escande, D. F., Fassina, A., Felici, F., Ferro, A., Finotti, C., Franz, P., Frassinetti, Lorenzo, Gaio, E., Ghezzi, F., Giudicotti, L., Gnesotto, F., Gobbin, M., Gonzalez, W. A., Grando, L., Guo, S. C., Hanson, J. D., Hirshman, S. P., Innocente, P., Jackson, J. L., Kiyama, S., Komm, M., Kudlacek, O., Laguardia, L., Li, C., Liu, B., Liu, S. F., Liu, Y. Q., Lopez-Bruna, D., Lorenzini, R., Luce, T. C., Luchetta, A., Maistrello, A., Manduchi, G., Mansfield, D. K., 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., Sajo-Bohus, L., Sakakita, H., Sanchez, R., Sarff, J. S., Sattin, F., Scarin, P., Schmitz, O., Schneider, W., Siragusa, M., Sonato, P., Spada, E., Spagnolo, S., Spolaore, M., Spong, D. A., 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., Visona, N., White, R. B., Xanthopoulos, P., Xu, X. Y., Yanovskiy, V., Zamengo, A., Zanca, P., Zaniol, B., Zanotto, L., Zhang, Y., and Zilli, E.

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., QC 20170802

Published
2017
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36. Overview of the RFX-mod fusion science activity

Author

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, Zilli, E, ZUIN, MATTEO, DAL BELLO, SILVIA, MARRELLI, LIONELLO, Puiatti, M. E., AGOSTINETTI, PIERO, AGOSTINI, MATTEO, ANTONI, VANNI, AURIEMMA, FULVIO, BARBISAN, MARCO, BARBUI, TULLIO, BARUZZO, MATTEO, Belli, F., BETTINI, PAOLO, Bigi, M., Bilel, R., Boldrin, M., BOLZONELLA, TOMMASO, BONFIGLIO, DANIELE, BROMBIN, MATTEO, BUFFA, ANTONIO, BUSTREO, CHIARA, CANTON, ALESSANDRA MARIA, CAPPELLO, SUSANNA, Carraro, L., Cavazzana, R., CESTER, DAVIDE, Chacon, L., CHITARIN, GIUSEPPE, Cooper, W. A., CORDARO, LUIGI, DALLA PALMA, MAURO, DEAMBROSIS, SILVIA MARIA, Delogu, R., De Lorenzi, A., DE MASI, GIANLUCA, Dong, J. Q., Escande, D. F., FASSINA, ALESSANDRO, Felici, F., Ferro, A., FINOTTI, CLAUDIO, Franz, P., FRASSINETTI, LORENZO, Gaio, E., GHEZZI, FEDERICO, GIUDICOTTI, LEONARDO, GNESOTTO, FRANCESCO, GOBBIN, MARCO, GONZALEZ, WINDER ALEXANDER, GRANDO, LUCA, Guo, S. C., Hanson, J. D., Hirshman, S. P., Innocente, P., Jackson, J. L., Kiyama, S., Komm, M., KUDLACEK, ONDREJ, LAGUARDIA, ANNA LUCIA, Li, C., Liu, B., Liu, S. F., Liu, Y. Q., López Bruna, D., Lorenzini, R., Luce, T. C., LUCHETTA, ADRIANO FRANCESCO, MAISTRELLO, ALBERTO, MANDUCHI, GABRIELE, Mansfield, D. K., Marchiori, G., MARCONATO, NICOLO', Marcuzzi, D., MARTIN, PIERO, MARTINES, EMILIO, MARTINI, STEFANO, Mazzitelli, G., Mccormack, O., Miorin, E., MOMO, BARBARA, MORESCO, MAURIZIO, 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. S., Sattin, F., Scarin, P., Schmitz, O., Schneider, W., Siragusa, M., Sonato, P., Spada, E., Spagnolo, S., Spolaore, M., Spong, D. A., 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. B., Xanthopoulos, P., Xu, X. Y., Yanovskiy, V., Zamengo, A., Zanca, P., Zaniol, B., Zanotto, L., Zhang, Y., Zilli, E., 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, Zilli, E, ZUIN, MATTEO, DAL BELLO, SILVIA, MARRELLI, LIONELLO, Puiatti, M. E., AGOSTINETTI, PIERO, AGOSTINI, MATTEO, ANTONI, VANNI, AURIEMMA, FULVIO, BARBISAN, MARCO, BARBUI, TULLIO, BARUZZO, MATTEO, Belli, F., BETTINI, PAOLO, Bigi, M., Bilel, R., Boldrin, M., BOLZONELLA, TOMMASO, BONFIGLIO, DANIELE, BROMBIN, MATTEO, BUFFA, ANTONIO, BUSTREO, CHIARA, CANTON, ALESSANDRA MARIA, CAPPELLO, SUSANNA, Carraro, L., Cavazzana, R., CESTER, DAVIDE, Chacon, L., CHITARIN, GIUSEPPE, Cooper, W. A., CORDARO, LUIGI, DALLA PALMA, MAURO, DEAMBROSIS, SILVIA MARIA, Delogu, R., De Lorenzi, A., DE MASI, GIANLUCA, Dong, J. Q., Escande, D. F., FASSINA, ALESSANDRO, Felici, F., Ferro, A., FINOTTI, CLAUDIO, Franz, P., FRASSINETTI, LORENZO, Gaio, E., GHEZZI, FEDERICO, GIUDICOTTI, LEONARDO, GNESOTTO, FRANCESCO, GOBBIN, MARCO, GONZALEZ, WINDER ALEXANDER, GRANDO, LUCA, Guo, S. C., Hanson, J. D., Hirshman, S. P., Innocente, P., Jackson, J. L., Kiyama, S., Komm, M., KUDLACEK, ONDREJ, LAGUARDIA, ANNA LUCIA, Li, C., Liu, B., Liu, S. F., Liu, Y. Q., López Bruna, D., Lorenzini, R., Luce, T. C., LUCHETTA, ADRIANO FRANCESCO, MAISTRELLO, ALBERTO, MANDUCHI, GABRIELE, Mansfield, D. K., Marchiori, G., MARCONATO, NICOLO', Marcuzzi, D., MARTIN, PIERO, MARTINES, EMILIO, MARTINI, STEFANO, Mazzitelli, G., Mccormack, O., Miorin, E., MOMO, BARBARA, MORESCO, MAURIZIO, 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. S., Sattin, F., Scarin, P., Schmitz, O., Schneider, W., Siragusa, M., Sonato, P., Spada, E., Spagnolo, S., Spolaore, M., Spong, D. A., 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. B., Xanthopoulos, P., Xu, X. Y., Yanovskiy, V., Zamengo, A., Zanca, P., Zaniol, B., Zanotto, L., Zhang, Y., and Zilli, E.

Abstract

This paper reports the main recent results of the RFX-mod fusion science activity. The RFX-mod device is characterized by a unique exibility in terms of accessible magnetic con gurations. Axisymmetric and helically shaped reversed- eld 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 con gurations in between the two, the so-called ultra-low q ones, has been explored, with the aim of studying speci c 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 speci c 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 rst transitions to an improved con nement scenario in circular and D-shaped tokamak plasmas have been obtained thanks to an active modi cation of the edge electric eld through a polarized electrode. The experiments are supported by intense modeling with 3D MHD, gyrokinetic, guiding center and transport codes. Proposed modi cations 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 brie y presented.

Published
2017

41. Runaway electron mitigation by resonant and non-resonant magnetic perturbations in RFX-mod tokamak discharges

Author

Marco Gobbin, Valisa, M., White, R. B., Marrelli, L., Piovesan, P., and Puiatti, M. E.

Abstract

Understanding the mechanisms behind Runaway Electron (RE) generation and the ways RE formation can be prevented is of paramount importance for future fusion reactors. The injection of massive gas into the plasma is the main solution presently envisaged to avoid the RE avalanche. Also other strategies have been developed to enhance the RE decorrelation as the application of external magnetic perturbations (MP) [1]. The RFX-mod device [2], which can be run as a Tokamak, is equipped with an advanced system for the control of Magnetohydrodynamic modes based on 192 saddle coils independently fed and on a state of the art real-time hardware and software architecture [3]; for this reason, it is particularly suited to study the possible impact on RE de-confinement in response of applied magnetic perturbations with different modal numbers and amplitude. The presence and the amount of fast electrons in RFX-mod can be revealed and analyzed by several diagnostics like the soft-xray tomography, blind CCD cameras and in particular 2 scintillators, which allow the detection of hard-x-rays produced when the high energy electrons impact with the wall. This work presents the necessary conditions for mitigation and control of RE via MP at different density levels have been studied, thus contributing to the Tokamak scaling laws [4]. Recent experiments are promising: we find that RE losses are significantly enhanced in low-q plasmas when the applied 3D field resonates with the m=2/n=1 external kink; in this case the plasma response amplifies the external field and thus increases the MP decorrelation efficacy. Resonant field amplification effects may play a role in RE decorrelation also in larger tokamaks. The mechanisms generating RE and the effect of the MP on their confinement are interpreted by the ORBIT code [5], which integrates the guiding center motion equations of test particles and has been recently updated to a relativistic version. The role played by different magnetic equilibria, hence also of different resonant modes, on the energy of RE and on their loss rates is investigated. ORBIT simulations indicate that RE enhanced losses are associated to a raised level of stochasticity, the effect being more pronounced when the MP amplitude is higher and internally resonant. [1] Lehnen et al. PRL 100. 255003 (2008) [2] Sonato P et al 2003 Fusion Eng. Des. 66 161 [3] Marrelli L et al 2007 Plasma Phys. Control. Fusion 49 B359 [4] Granetz R.S. et al 2014 Phys. Plasmas 21 072506 [5] White R.B. et al.1984 Phys. Fluids 27 2455

Published
2015

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

Author

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, Puiatti M E, 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 E, Chitarin G, Ciaccio G, Cooper W A, Dalla Palma M, Deambrosis S, Delogu R, De Lorenzi A, De Masi G, Dong J Q, Escande D F, Esposito B, Fassina A, Fellin F, Ferro A, Finotti C, Franz P, Frassinetti L, Palumbo M Furno, Gaio E, Ghezzi F, Giudicotti L, Gnesotto F, Gobbin M, Gonzales W A, Grando L, Guo S C, Hanson J D, Hirshman S P, Innocente P, Jackson J L, Kiyama S, Komm M, Laguardia L, Li C, Liu S F, Liu Y Q, Lorenzini R, Luce T C, Luchetta A, Maistrello A, Manduchi G, Mansfield D K, 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 L, Rostagni G, Ruset C, Ruzzon A, Sajo-Bohus L, Sakakita H, Sanchez R, Sarff J S, Sartori E, Sattin F, Scaggion A, Scarin P, Schmitz O, Sonato P, Spada E, Spagnolo S, Spolaore M, Spong D A, Spizzo G, Stevanato L, Takechi M, Taliercio C, Terranova D, Trevisan G L, Urso G, Valente M, Valisa M, Veranda M, Vianello N, Viesti G, Villone F, Vincenzi P, Visona' N, Wang Z R, White R B, Xanthopoulos P, Xu X Y, Yanovskiy V, Zamengo A, Zanca P, Zaniol B, Zanotto L, Zilli E, Zuin M, 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, Puiatti M E, 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 E, Chitarin G, Ciaccio G, Cooper W A, Dalla Palma M, Deambrosis S, Delogu R, De Lorenzi A, De Masi G, Dong J Q, Escande D F, Esposito B, Fassina A, Fellin F, Ferro A, Finotti C, Franz P, Frassinetti L, Palumbo M Furno, Gaio E, Ghezzi F, Giudicotti L, Gnesotto F, Gobbin M, Gonzales W A, Grando L, Guo S C, Hanson J D, Hirshman S P, Innocente P, Jackson J L, Kiyama S, Komm M, Laguardia L, Li C, Liu S F, Liu Y Q, Lorenzini R, Luce T C, Luchetta A, Maistrello A, Manduchi G, Mansfield D K, 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 L, Rostagni G, Ruset C, Ruzzon A, Sajo-Bohus L, Sakakita H, Sanchez R, Sarff J S, Sartori E, Sattin F, Scaggion A, Scarin P, Schmitz O, Sonato P, Spada E, Spagnolo S, Spolaore M, Spong D A, Spizzo G, Stevanato L, Takechi M, Taliercio C, Terranova D, Trevisan G L, Urso G, Valente M, Valisa M, Veranda M, Vianello N, Viesti G, Villone F, Vincenzi P, Visona' N, Wang Z R, White R B, Xanthopoulos P, Xu X Y, Yanovskiy V, Zamengo A, Zanca P, Zaniol B, Zanotto L, Zilli E, and Zuin M

Abstract

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

Published
2015

46. Density limit studies in the tokamak and the reversed-field pinch

Author

Spizzo, G, Pucella, G, Tudisco, O, Zuin, M, Agostini, M, Alessi, E, Auriemma, F, Bin, W, Buratti, P, Carraro, L, Cavazzana, R, Ciaccio, G, Masi, G, Esposito, B, Galperti, C, Garavaglia, S, Granucci, G, Marinucci, M, Marrelli, L, Martines, E, Mazzotta, C, Minelli, D, Moro, A, Puiatti, M, Scarin, P, Sozzi, C, Spolaore, M, Schmitz, O, Vianello, N, White, R, Spizzo, G., Pucella, G., Tudisco, O., Zuin, M., Agostini, M., Alessi, E., AURIEMMA, FULVIO, Bin, W., Buratti, P., Carraro, L., Cavazzana, R., CIACCIO, GIOVANNI, Masi, G. De, Esposito, B., Galperti, C., Garavaglia, S., Granucci, G., Marinucci, M., MARRELLI, LIONELLO, MARTINES, EMILIO, Mazzotta, C., Minelli, D., Moro, A., Puiatti, M. E., Scarin, P., Sozzi, C., Spolaore, M., Schmitz, O., Vianello, N., White, R. B., Spizzo, G, Pucella, G, Tudisco, O, Zuin, M, Agostini, M, Alessi, E, Auriemma, F, Bin, W, Buratti, P, Carraro, L, Cavazzana, R, Ciaccio, G, Masi, G, Esposito, B, Galperti, C, Garavaglia, S, Granucci, G, Marinucci, M, Marrelli, L, Martines, E, Mazzotta, C, Minelli, D, Moro, A, Puiatti, M, Scarin, P, Sozzi, C, Spolaore, M, Schmitz, O, Vianello, N, White, R, Spizzo, G., Pucella, G., Tudisco, O., Zuin, M., Agostini, M., Alessi, E., AURIEMMA, FULVIO, Bin, W., Buratti, P., Carraro, L., Cavazzana, R., CIACCIO, GIOVANNI, Masi, G. De, Esposito, B., Galperti, C., Garavaglia, S., Granucci, G., Marinucci, M., MARRELLI, LIONELLO, MARTINES, EMILIO, Mazzotta, C., Minelli, D., Moro, A., Puiatti, M. E., Scarin, P., Sozzi, C., Spolaore, M., Schmitz, O., Vianello, N., and White, R. B.

Abstract

The ITER scenarios and the project of DEMO involve stable operation above the Greenwald density, which justifies efforts to understand and overcome the density limit, this last observed as a disruptive termination of tokamak discharges and a thermal crash (with no disruption) of stellarator and reversed-field pinch (RFP) ones. Both in the tokamak and the RFP, new findings show that the high density limit is not governed by a unique, theoretically well-determined physical phenomenon, but by a combination of complex mechanisms involving two-fluid effects, electrostatic plasma response to magnetic islands and plasma-wall interaction. In this paper we will show new evidence challenging the traditional picture of the 'Greenwald limit', in particular with reference to the role of thermal instabilities and the edge radial electric field Er in the development of this limit.

Published
2015

47. LETTERS.

Author

LEAVELL, R., DEWEY, CAROL P., ANEIRO, GEORGE, STROUP, RUSSELL C., SCHMIDT, J. E., O'CONNER, CATHLEEN, DYKES, E. W., HESS, GEORGE J., LIEBERTHAL, JULES M., BRYAN, CHARLES C., SEMMION, RUTH, WHITE, R. B., TRATTNER, JOHN H., CHIARIELLO, JOHN, MENARD, WILMON B., COON, SAM, DOWNING, JOE, SELLERS, VIRGIL A., and HANSEN, ARCHER ELLIS

Subjects
VICE-Presidents of the United States, PUBLIC schools
Published
1955

48. Benchmark of Orbit and NEMATO codes on magnetic topology reconstruction in RFPs

Author

Ciaccio G., Veranda M., Bonfiglio D., Cappello S., Spizzo G., Chacón L., and White R. B.

Abstract

\textsc{Orbit} is a Hamiltonian guiding center code which describes test-particle motion in an electromagnetic field.\footnote{R. B. White and M. S. Chance, Phys. Fluids B \textbf{27} (1984) 2455} In the limit $\rho_{\parallel} \rightarrow 0$, $\rho_{\parallel} = v_{\parallel}/B$ it can be used to trace the magnetic field topology, in a way in all respects similar to simplectic codes. \textsc{NEMATO}\footnote{J. M. Finn, L. Chac\'on, Phys. of Plasma \textbf{12} (2005) 054503} is a field-line tracing code, implemented to integrate solenoidal flows for incompressible fluid dynamics, with automatic volume preservation. In a practical application, the two codes have been used to study the structure of the $q = 0$ island chain which characterizes the RFP edge and its behavior as a function of the reversal parameter $F=B_ {\phi}(a)/\langle B_{\phi} \rangle$. As input for both codes we used the snapshot of a 3D nonlinear MHD visco-resistive simulation (SpeCyl code). The first benchmarking test employs a Hamiltonian (single-mode) magnetic field configuration. Both codes successfully yield field lines which follow flux surfaces in both the $m = 1$ and $m = 0$ cases. The comparison between the codes has been successfully extended to a chaotic magnetic field configuration, including many modes.

Published
2011

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