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16 results on '"K. Sarksian"'

1. Reaction of turbulence at the edge and in the center of the plasma column to pulsed impurity injection caused by the sputtering of the wall coating in L-2M stellarator

Author

L. V. Kolik, N. K. Kharchev, G. M. Batanov, E. M. Konchekov, K. Sarksian, A. A. Letunov, Nina N. Skvortsova, I. Yu. Vafin, A. A. Kharchevskii, D. G. Vasilkov, A. I. Meshcheryakov, S. V. Shchepetov, M. S. Berezhetskii, I. A. Grishina, N. F. Larionova, V. P. Logvinenko, Yu. V. Khol’nov, A. E. Petrov, V. D. Borzosekov, D. V. Malakhov, S. E. Grebenshchikov, and V. D. Stepakhin

Subjects
Materials science, Physics and Astronomy (miscellaneous), Turbulence, Plasma, engineering.material, Condensed Matter Physics, 01 natural sciences, Electron cyclotron resonance, 010305 fluids & plasmas, law.invention, Coating, Sputtering, law, Impurity, 0103 physical sciences, engineering, Atomic physics, Magnetohydrodynamics, 010306 general physics, Stellarator
Abstract

Impurity injection into plasma caused by the sputtering of the wall coating in the L-2M stellarator during auxiliary electron cyclotron resonance heating leads to a change in the level of plasma density fluctuations with frequencies above 0.25 MHz: suppression of long-wavelength (k ⊥ = 2 cm–1) density fluctuations in the edge plasma, intensification of short-wavelength (k ⊥ = 30 cm–1) and long-wavelength (k ⊥ = 1 cm–1) fluctuations at the midradius of the plasma column, and intensification of short-wavelength fluctuations (k ⊥ = 20 cm–1) in the plasma center (including the gyroresonance region). At the same time, the level of fluctuations with frequencies below 0.25 MHz remains unchanged. In the edge plasma, a decrease in the plasma potential and suppression of its fluctuations is observed during impurity injection, which also causes an increase in MHD activity.

Published
2017
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2. 3D effects on transport and plasma control in the TJ-II stellarator

Author

G. Wolfers, E. Ascasíbar, F. Fernández-Marina, Javier Alonso, Macarena Liniers, F. Martín-Díaz, P. Méndez, A.S. Kozachoek, A. Cappa, Jesús Vega, E. Oyarzábal, K. Sarksian, María Sánchez, M. Medrano, J. Hernández, J. Botija, J. Martínez-Fernández, Marley Vanegas Chamorro, Isabel García-Cortés, B. Momo, K. J. McCarthy, A. Tolkachev, D. Alegre, A. Pereira, L. I. Krupnik, G. Velasco, R. Carrasco, Raul Moreno, Ivan Calvo, U. Losada, F. Medina, E. Sánchez, A.A. Chmyga, G. Martín-Gómez, J. Guasp, F. Castejón, F. J. Miguel, A. Jiménez-Denche, N. Panadero, M. Borchardt, Jesús Herranz, B. Rojo, A. Molinero, L.G. Eliseev, A. Alonso, R. García-Gómez, E. R. Solano, J. Olivares, T. Estrada, Roman Hatzky, M. A. Ochando, J.M. Barcala, R. Merino, F. Lapayese, J.A. Sebastián, Y. Narushima, Shinsuke Satake, L. Melón, E. Sánchez-Sarabia, I. Kirpitchev, A. Martin de Aguilera, A.D. Komarov, M. Martínez, A. de la Peña, F. Martín-Hernández, B. Liu, C. Hidalgo, G. Catalán, Francisco L. Tabarés, E. Rincón, A.B. Martín-Rojo, J. M. Garcia-Regana, B. J. Sun, B. van Milligen, S. Cabrera, J. Sánchez, S. Petrov, A. de Bustos, M. A. Pedrosa, C. Rodríguez, B. Zurro, J. Hernanz, Eric Hollmann, A. Ros, Carlos A. Silva, J.L. de Pablos, S. Tallents, Luis F. Pacios, Ralf Kleiber, A. de Castro, José Luis Velasco, Luis Rios, B. López-Miranda, I. Pastor, E. Poveda, A. E. Petrov, P. Monreal, J. López-Razola, Luis Garcia, G.A. Rattá, M. Navarro, D. López-Bruna, E. de la Cal, J. M. Fontdecaba, A. Portas, M. Yokoyama, D. Tafalla, E. de la Luna, A. Soleto, R. Castro, D. Baião, Andreas Dinklage, A. López-Fraguas, A.V. Melnikov, A. Baciero, E. Blanco, and I. S. Nedzelskiy

Subjects
Physics, Nuclear and High Energy Physics, Magnetic confinement fusion, Plasma confinement, Transport theory, Condensed Matter Physics, 01 natural sciences, 7. Clean energy, Charged particle, 010305 fluids & plasmas, Ion, law.invention, law, Dispersion relation, 0103 physical sciences, Atomic physics, 010306 general physics, Stellarator, Plasma control
Abstract

The effects of 3D geometry are explored in TJ-II from two relevant points of view: neoclassical transport and modification of stability and dispersion relation of waves. Particle fuelling and impurity transport are studied considering the 3D transport properties, paying attention to both neoclassical transport and other possible mechanisms. The effects of the 3D magnetic topology on stability, confinement and Alfvén Eigenmodes properties are also explored, showing the possibility of controlling Alfvén modes by modifying the configuration; the onset of modes similar to geodesic acoustic modes are driven by fast electrons or fast ions; and the weak effect of magnetic well on confinement. Finally, we show innovative power exhaust scenarios using liquid metals.

Published
2017

3. Boron Nitride and Titanium Diboride Synthesis Initiated by Microwave Discharge in Ti–B Powder Mixture in Nitrogen Atmosphere

Author

E. M. Konchekov, D. V. Malakhov, A. A. Letunov, N. K. Kharchev, N. K. Berezhetskaya, Ekaterina A. Obraztsova, V. D. Stepakhin, E.A. Vasileva, A. E. Petrov, K. Sarksian, V. D. Borzosekov, A.A. Zolotukhin, Nina N. Skvortsova, Elena D. Obraztsova, L. V. Kolik, G. M. Batanov, and L. D. Iskhakova

Subjects
chemistry.chemical_compound, Materials science, chemistry, Boron nitride, Inorganic chemistry, Nitrogen atmosphere, Electrical and Electronic Engineering, Nitride, Titanium diboride, Microwave, Powder mixture, Electronic, Optical and Magnetic Materials
Published
2013
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4. Overview of TJ-II experiments

Author

J. Sánchez, M. Acedo, A. Alonso, J. Alonso, P. Alvarez, F. de Aragón, E. Ascasíbar, A. Baciero, R. Balbín, L. Barrera, E. Blanco, J. Botija, B. Brañas, E. de la Cal, E. Calderón, I. Calvo, A. Cappa, J.A. Carmona, B.A. Carreras, R. Carrasco, F. Castejón, G. Catalán, A.A. Chmyga, N.B. Dreval, M. Chamorro, S. Eguilior, J. Encabo, L. Eliseev, T. Estrada, A. Fernández, R. Fernández, J.A. Ferreira, J.M. Fontdecaba, C. Fuentes, J. de la Gama, A. García, L. García, I. García-Cortés, J.M. García-Regaña, B. Gonçalves, J. Guasp, J. Herranz, A. Hidalgo, C. Hidalgo, R. Jiménez-Gómez, J.A. Jiménez, D. Jiménez, I. Kirpitchev, A.D. Komarov, A.S. Kozachok, L. Krupnik, F. Lapayese, M. Liniers, D. López-Bruna, A. López-Fraguas, J. López-Rázola, A. López-Sánchez, E. de la Luna, G. Marcon, F. Martín, L. Martínez-Fresno, K.J. McCarthy, F. Medina, M. Medrano, A.V. Melnikov, P. Méndez, E. Mirones, B. van Milligen, I.S. Nedzelskiy, M. Ochando, J. Olivares, R. Orozco, P. Ortiz, J.L. de Pablos, L. Pacios, I. Pastor, M.A. Pedrosa, A. de la Peña, A. Pereira, D. Pérez-Risco, A. Petrov, S. Petrov, A. Portas, D. Rapisarda, L. Ríos, C. Rodríguez, L. Rodríguez-Rodrigo, E. Rodríguez-Solano, J. Romero, A. Ros, A. Salas, E. Sánchez, M. Sánchez, E. Sánchez-Sarabia, X. Sarasola, K. Sarksian, C. Silva, S. Schchepetov, N. Skvortsova, A. Soleto, F. Tabarés, D. Tafalla, J. Tera, A. Tolkachev, V. Tribaldos, V.I. Vargas, J. Vega, G. Velasco, M. Weber, G. Wolfers, S.J. Zweben, and B. Zurro

Subjects
Nuclear and High Energy Physics, Condensed Matter Physics
Published
2007
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5. Overview of TJ-II experiments

Author

C Hidalgo, C Alejaldre, A Alonso, J Alonso, L Almoguera, F. de Aragón, E Ascasíbar, A Baciero, R Balbín, E Blanco, J Botija, B Brañas, E Calderón, A Cappa, J.A Carmona, R Carrasco, F Castejón, J.R Cepero, A.A Chmyga, J Doncel, N.B Dreval, S Eguilior, L Eliseev, T Estrada, J.A Ferreira, A Fernández, J.M Fontdecaba, C Fuentes, A García, I García-Cortés, B Gonçalves, J Guasp, J Herranz, A Hidalgo, R Jiménez, J.A Jiménez, D Jiménez-Rey, I Kirpitchev, S.M Khrebtov, A.D Komarov, A.S Kozachok, L Krupnik, F Lapayese, M Liniers, D López-Bruna, A López-Fraguas, J López-Rázola, A López-Sánchez, E. de la Luna, G Marcon, R Martín, K.J McCarthy, F Medina, M Medrano, A.V Melnikov, P Méndez, B. van Milligen, I.S Nedzelskiy, M Ochando, O Orozco, J.L. de Pablos, L Pacios, I Pastor, M.A Pedrosa, A. de la Peña, A Pereira, A Petrov, S Petrov, A Portas, D Rapisarda, L Rodríguez-Rodrigo, E Rodríguez-Solano, J Romero, A Salas, E Sánchez, J Sánchez, M Sánchez, K Sarksian, C Silva, S Schchepetov, N Skvortsova, F Tabarés, D Tafalla, A Tolkachev, V Tribaldos, I Vargas, J Vega, G Wolfers, and B Zurro

Subjects
Nuclear and High Energy Physics, Condensed Matter Physics
Published
2005
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6. Confinement and stability on the TJ-II stellarator

Author

A. Cappa, J R Cepero, E. de la Luna, Kieran J. McCarthy, A. López-Sánchez, K. Likin, L Rodríguez-Rodrigo, S. Schchepetov, A Salas, C. Hidalgo, L. I. Krupnik, E. Sánchez, A.V. Melnikov, J.A. Jiménez, R. Carrasco, B. Brañas, M. Liniers, E. Blanco, J.A. Romero, C. Fuentes, J. Herranz, Enrique Ascasibar, J. Guasp, C Alejaldre, I. Kirpitchev, M. A. Pedrosa, B. van Milligen, M Blaumoser, A. de la Peña, Jesús Vega, A.A. Chmyga, F. Medina, P. Méndez, M. A. Ochando, L.G. Eliseev, R. Balbín, B. Zurro, Angela Garcia, Francisco Castejón, B. Gonçalves, A. Hidalgo, S. Petrov, J. Sanchez, C F A Varandas, Ángela Fernández, A. Portas, Victor Tribaldos, D. López-Bruna, A. E. Petrov, J Doncel, J. López-Razola, A. S. Kozachok, L. Pacios, K. Sarksian, O. I. Fedyanin, I. García-Cortés, A. Baciero, S. M. Khrebtov, I.S. Nedzelskiy, M. Medrano, I. Pastor, Francisco L. Tabarés, F. Lapayese, D. Tafalla, J M Fontdecaba, T. Estrada, N. B. Dreval, A. Malaquias, A. D. Komarov, Nina N. Skvortsova, A. López-Fraguas, L Almoguera, Romualdo Martín, S Eguilior, J. A. Alonso, and J. Botija

Subjects
Materials science, Turbulence, Magnetic confinement fusion, Plasma, Condensed Matter Physics, Stability (probability), law.invention, Shear (sheet metal), Core (optical fiber), Coupling (physics), Nuclear Energy and Engineering, Physics::Plasma Physics, law, Physics::Space Physics, Atomic physics, Stellarator
Abstract

This paper describes a series of experiments performed in TJ-II stellarator with the aim of studying the influence of magnetic configuration on stability and transport properties of TJ-II plasmas. Plasma potential profiles have been measured in several configurations up to the plasma core with the heavy ion beam probe diagnostic. Low-order rational surfaces have been positioned at different plasma radii observing the effect on transport features. Plasma edge turbulent transport has been studied in configurations that are marginally stable due to decreased magnetic well. Results show a dynamical coupling between gradients and turbulent transport. Experiments on the influence of magnetic shear on confinement are reported. Global confinement issues as well as enhanced confinement regimes found in TJ-II are discussed as well.

Published
2002
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7. Statistical properties and radial structure of plasma turbulence in the boundary region of the L2-M stellarator

Author

B. van Milligen, N. K. Kharchev, C. Hidalgo, J A Jiménez, G. M. Batanov, M. A. Pedrosa, Yu. V. Khol’nov, O I Fedianin, Nina N. Skvortsova, S. V. Shchepetov, and K. Sarksian

Subjects
Physics, Resistive touchscreen, Condensed matter physics, Turbulence, Plasma turbulence, Plasma, Condensed Matter Physics, Magnetic flux, law.invention, Computational physics, Nuclear Energy and Engineering, law, Boundary region, Stellarator, Coherence (physics)
Abstract

The structure of fluctuations and turbulent transport have been investigated in the plasma boundary region of the L2-M stellarator. Normalized fluctuation levels are in the range (3-20)% and fluctuations are dominated by frequencies below 300 kHz. In the edge plasma region located inside the last closed magnetic flux surface the radial coherence of fluctuations is due to high-frequency fluctuations (>100 kHz). The poloidal coherence is dominated by low frequencies. Linear coupling of resistive interchange modes is considered a candidate to explain the existence of highly radially correlated fluctuations in the high-frequency range.

Published
1998
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8. Synthesis of micro- and nanostructures with controllable composition in the chain plasma-chemical reactions initiated by the radiation of a powerful gyrotron in the mixtures of metal-dielectric powders

Author

E.M. Konchekov, N. K. Kharchev, L. V. Kolik, A.E. Petrov, G. M. Batanov, E.A. Obraztsova, V.D. Borzosekov, A. A. Letunov, N. S. Akhmadullina, K. Sarksian, O. N. Shishilov, V. D. Stepakhin, N.N. Skvortsova, and D. V. Malakhov

Subjects
010302 applied physics, Nanostructure, Materials science, Physics, QC1-999, Nanotechnology, 02 engineering and technology, Plasma, Dielectric, Radiation, 021001 nanoscience & nanotechnology, 01 natural sciences, Chemical reaction, law.invention, Metal, law, visual_art, Gyrotron, 0103 physical sciences, visual_art.visual_art_medium, 0210 nano-technology
Published
2017
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9. Dynamics of flows and confinement in the TJ-II stellarator

Author

Juan Miguel Insúa Arévalo, Enrique Ascasibar, S. Petrov, A. Martin, M. A. Pedrosa, L. I. Krupnik, A. Cappa, E. Oyarzábal, E. Sánchez, R. Carrasco, J. Hernández, E. R. Solano, A. E. Petrov, A. S. Kozachok, A.D. Komarov, Ralf Kleiber, J. López-Razola, D. López-Bruna, A. Tolkachev, M. Sánchez, E. Sánchez-Sarabia, A. de la Peña, G. Velasco, Kieran J. McCarthy, J.A. Sebastián, A. Soleto, Roman Hatzky, J. Vega, M. Navarro, J. Hernanz, M. A. Ochando, C. Hidalgo, D. Tafalla, P. Méndez, I. Kirpitchev, José Luis Velasco, B. J. Sun, I.S. Nedzelskiy, Luis Garcia, F. Martín-Hernández, J. Martínez-Fernández, M. Medrano, I. Pastor, Carlos A. Silva, Marley Vanegas Chamorro, M. Borchardt, J.A. Jiménez, A. Pereira, C. Rodríguez, A. Baciero, P. Álvarez, P. Monreal, F. Fernández, K. Sarksian, A. Alonso, L. Ríos, J. Herranz, Francisco L. Tabarés, P. García-Sánchez, F. Lapayese, R. García-Gómez, A. Bustos, A. Jiménez-Denche, D. Carralero, D. Alegre, B. van Milligen, J. Sánchez, L. Pacios, M. Tereshchenko, L.G. Eliseev, J. Olivares, L. Melón, A. Portas, J. A. Alonso, E. de la Cal, J. M. Fontdecaba, A.V. Melnikov, E. Blanco, A.A. Chmyga, J. Botija, T. Estrada, J.A. Romero, Ivan Calvo, J.L. de Pablos, R. Castro, Francisco Castejón, B. Rojo, E. Rincón, G. Catalán, G. Wolfers, F. Martín-Díaz, F. Medina, A. López-Fraguas, M. Liniers, S. da Graca, A.B. Martín-Rojo, B. Zurro, A. Ros, J. Guasp, and D. Baiao

Subjects
Physics, Nuclear and High Energy Physics, Work (thermodynamics), Turbulence, Flow (psychology), Observable, Mechanics, Condensed Matter Physics, law.invention, Physics::Fluid Dynamics, Viscosity, law, Relaxation (physics), Statistical physics, Shear flow, Stellarator
Abstract

This work deals with the results on flow dynamics in TJ-II plasmas under Li-coated wall conditions, which produces low recycling and facilitates the density control and access to improved confinement transitions. The low-density transition, characterized by the emergence of the shear flow layer, is described from first principles and within the framework of neoclassical theory. The vanishing of the neoclassical viscosity when approaching the transition from below explains the observation of a number of turbulent phenomena reported in TJ-II in recent years; a unifying picture is provided in which zonal, i.e. large scale, radially structured, perturbations are observable when the neoclassical damping is sufficiently small. Preliminary linear, collisionless gyrokinetic simulations are carried out to assess that the measured time scale of relaxation of such perturbations is reasonably understood theoretically. In higher density regimes, the physical mechanisms behind the L–H transition have been experimentally studied. The spatial, temporal and spectral structure of the interaction between turbulence and flows has been studied close to the L–H transition threshold conditions. The temporal dynamics of the turbulence-flow interaction displays a predator–prey relationship and both radial outward and inward propagation velocities of the turbulence-flow front have been measured. Finally, a non-linear relation between turbulent fluxes and gradients is observed.

Published
2013

10. Overview of TJ-II experiments

Author

T. Madeira, G. Wolfers, J. López-Razola, A.V. Melnikov, A. Molinero, E. Blanco, A. Baciero, J. Martínez-Fernández, P. Álvarez, F. Martín-Díaz, Luis Garcia, F. Medina, J. Olivares, A. Soleto, E. Rincón, M. Weber, J. Vega, A. Alonso, I.S. Nedzelskiy, A. Petrov, M. Medrano, I. Pastor, Carlos A. Silva, G. Catalán, G. Sánchez-Burillo, J.A. Romero, J.A. Jiménez, A. Pereira, M. Acedo, A. Portas, D. Tafalla, L. Pacios, A. Cappa, A. Tolkachev, P. Méndez, J.A. Sebastián, J. A. Alonso, F. Martín-Hernández, S. Petrov, E. de la Cal, Francisco Castejón, Marley Vanegas Chamorro, B. Zurro, E. Oyarzábal, C. Rodríguez, L. Esteban, Jorge Ferreira, D. Alegre, R. Jiménez-Gómez, A. Ros, M. Liniers, A. S. Kozachok, A.B. Martín-Rojo, J. M. Garcia-Regana, S. González, B. Rojo, R. García-Gómez, E. R. Solano, J. Hernanz, J. Botija, T. Happel, J. Guasp, A. D. Komarov, I. Kirpitchev, K. Sarksian, D. Baiao, Juan Miguel Insúa Arévalo, Ivan Calvo, J.M. Fontdecaba, José Luis Velasco, Benjamin A. Carreras, Antonio Gómez-Iglesias, P. García-Sánchez, A.A. Chmyga, Francisco L. Tabarés, F. Lapayese, T. Estrada, J. M. Reynolds, L. Melón, J. Sanchez, J. Tera, J. Herranz, A. Bustos, G.A. Rattá, D. Carralero, B. van Milligen, M. Navarro, M. A. Ochando, A. López-Fraguas, D. López-Bruna, A. de la Peña, R. Castro, L. I. Krupnik, E. Sánchez, R. Carrasco, M. Sánchez, G. Velasco, E. Mirones, J.L. de Pablos, Enrique Ascasibar, M. A. Pedrosa, A. Jiménez-Denche, L.G. Eliseev, E. Sánchez-Sarabia, L. Barrera, Kieran J. McCarthy, C. Hidalgo, and L. Ríos

Subjects
Physics, Nuclear and High Energy Physics, Turbulence, Magnetic confinement fusion, Mechanics, Plasma, Condensed Matter Physics, law.invention, Coupling (physics), Physics::Plasma Physics, law, Electric field, Physics::Space Physics, Limiter, Atomic physics, Topology (chemistry), Stellarator
Abstract

This paper presents an overview of experimental results and progress made in investigating the link between magnetic topology, electric fields and transport in the TJ-II stellarator. The smooth change from positive to negative electric field observed in the core region as the density is raised is correlated with global and local transport data. A statistical description of transport is emerging as a new way to describe the coupling between profiles, plasma flows and turbulence. TJ-II experiments show that the location of rational surfaces inside the plasma can, in some circumstances, provide a trigger for the development of core transitions, providing a critical test for the various models that have been proposed to explain the appearance of transport barriers in relation to magnetic topology. In the plasma core, perpendicular rotation is strongly coupled to plasma density, showing a reversal consistent with neoclassical expectations. In contrast, spontaneous sheared flows in the plasma edge appear to be coupled strongly to plasma turbulence, consistent with the expectation for turbulent driven flows. The local injection of hydrocarbons through a mobile limiter and the erosion produced by plasmas with well-known edge parameters opens the possibility of performing carbon transport studies, relevant for understanding co-deposit formation in fusion devices.

Published
2011
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11. Confinement studies in the TJ-II stellarator

Author

Francisco Castejón, A López-Fraguas, R. Carrasco, M Linier, S. E. Grebenshchikov, I Labrador, C. Fuentes, E. Sánchez, A Salas, L Almoguera, V Krivenski, A Fernández, I. Kirpitchev, Asunción Martínez Martínez, G van Dijk, M. A. Pedrosa, B. Brañas, M Blaumoser, O. I. Fedyanin, A. López-Sánchez, C Alejaldre, J. Guasp, K Likin, J A Jiménez, R Barth, I Garcí a-Cortés, Jesús Vega, A. Portas, Kieran J. McCarthy, A. de la Peña, E. de la Cal, E. de la Luna, C. Hidalgo, Francisco L. Tabarés, F. Lapayese, J R Cepero, J Herranz, L Rodríguez-Rodrigo, I Pastor, A García, J M Delgado, L. Pacios, M. Medrano, D. Tafalla, T. Estrada, P. Méndez, B. Zurro, J Qin, D Akulina, K. Sarksian, M. A. Ochando, H.J. van der Meiden, J Doncel, J. A. Alonso, A. I. Meshcheryakov, L. Martínez-Laso, C Dulya, A. Cappa, J. Botija, C Cremy, A. Baciero, J. Sanchez, R. Balbín, B. van Milligen, E Ascasí bar, Victor Tribaldos, R Martín, F. Medina, and N. K. Kharchev

Subjects
Physics, Shear (sheet metal), Range (particle radiation), Nuclear Energy and Engineering, Rational surface, law, Plasma, Atomic physics, Condensed Matter Physics, Stellarator, Electron cyclotron resonance, law.invention, Power density
Abstract

ECR (electron cyclotron resonance) heated plasmas have been studied in the low magnetic shear TJ-II stellarator (R = 1.5 m, a < 0.22 m, B = 1 T, f = 53.2 GHz, P-ECRH = 300 kW, power density = 1-25 W cm(-3)). Recent experiments have explored the flexibility of the TJ-II across a wide range of plasma volumes with different rotational transforms and rational surface densities. In this paper, the main results of this campaign are presented and, in particular, the influence of iota and rational surfaces on plasma profiles is discussed.

12. Confinement transitions in TJ-II under Li-coated wall conditions

Author

J.L. de Pablos, Francisco Castejón, R. Fernández-Gavilán, Victor Tribaldos, G. Catalán, V. I. Vargas, Marley Vanegas Chamorro, David Rapisarda, R. Balbín, E. Mirones, J. Botija, A. S. Kozachok, K. Sarksian, L. Esteban, R. Carrasco, G. Marcon, I. García-Cortés, A.D. Komarov, S. E. Lysenko, J.A. Jiménez, A. Pereira, J. Sánchez, J. A. Alonso, J. M. Carmona, E. Rincón, J. Hernanz, J. Tera, J. Herranz, A.A. Chmyga, M. Acedo, B. Zurro, José Luis Velasco, C. Rodríguez, Alfonso Tarancón, D. Jiménez-Rey, R. Castro, C. Fuentes, A. Ros, Enrique Ascasibar, F. Martín, L. Ríos, A. de la Peña, Jorge Ferreira, D. Tafalla, A. Tolkachev, Luis Garcia, D. Carralero, B. van Milligen, Yu.I. Taschev, M. Sánchez, G. Velasco, Ángela Fernández, L. I. Krupnik, A. Baciero, P. Álvarez, M. Liniers, M. A. Pedrosa, E. de la Cal, Ivan Calvo, A. Cappa, A. Jiménez-Denche, J. M. Fontdecaba, A. Soleto, J. M. Garcia-Regana, Nina N. Skvortsova, J. Vega, E. Sánchez, L. Pacios, A. de Bustos, T. Happel, D. López-Bruna, V. Maurin, T. Estrada, S. Petrov, P. Méndez, D. Pérez-Risco, J. Guasp, J.A. Sebastián, J. M. Reynolds, Alberto Alonso, G.A. Rattá, E. Sánchez-Sarabia, L.G. Eliseev, A.V. Melnikov, R. Jiménez-Gómez, A. López-Sánchez, A. Portas, Benjamin A. Carreras, M. A. Ochando, M. Weber, L. Barrera, Kieran J. McCarthy, E. Blanco, J. Olivares, G. Wolfers, D. G. Pretty, L. Guimarais, A Salas, German Perez, Francisco L. Tabarés, F. Lapayese, C. Hidalgo, F. Medina, A. López-Fraguas, J.A. Romero, E. R. Solano, I. Kirpitchev, S. Schchepetov, R. García-Gómez, I.S. Nedzelskiy, A. Petrov, M. Medrano, I. Pastor, Carlos A. Silva, and J. López-Razola

Subjects
Nuclear and High Energy Physics, Materials science, Density gradient, chemistry.chemical_element, Plasma, Condensed Matter Physics, Thermal diffusivity, Evaporation (deposition), law.invention, Ion, Vacuum evaporation, chemistry, law, Lithium, Atomic physics, Stellarator
Abstract

This paper presents the latest results on confinement studies in the TJ-II stellarator. The inherently strong plasma–wall interaction of TJ-II has been successfully reduced after lithium coating by vacuum evaporation. Besides H retention and low Z, Li was chosen because there exists a reactor-oriented interest in this element, thus giving special relevance to the investigation of its properties. The Li-coating has led to important changes in plasma performance. Particularly, the effective density limit in NBI plasmas has been extended reaching central values of 8 × 1019 m−3 and T e ≈ 250–300 eV, with peaked density, rather flat T e profiles and higher ion temperatures. Due to the achieved density control, a second type of transition has been added to the low density ones previously observed in ECRH plasmas: higher density transitions characterized by the fall in Hα emission, the onset of steep density gradient and the reduction in the turbulence; which are characteristics of transition to the H mode. Confinement studies in ECH plasmas indicate that lowest order magnetic resonances, even in a low shear environment, locally reduce the effective electron heat diffusivities, while Alfven eigenmodes destabilized in NBI plasmas can influence fast ion confinement.

13. Ballistic transport phenomena in TJ-II

Author

J. Herranz, B. van Milligen, Enrique Ascasibar, M. A. Ochando, M. A. Pedrosa, D. Tafalla, T. Estrada, K. Sarksian, J.A. Jiménez, Luis Garcia, J. Castellano, C. Hidalgo, E. de la Luna, Nina N. Skvortsova, Raul Sanchez, I. García-Cortés, Francisco L. Tabarés, I. Pastor, A. E. Petrov, Francisco Castejón, and F. Medina

Subjects
Physics, Nuclear and High Energy Physics, Turbulence, Magnetic confinement fusion, Mechanics, Plasma, Condensed Matter Physics, law.invention, law, Ballistic conduction, Pinch, Electron temperature, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, Stellarator, Pressure gradient
Abstract

Perturbative transport experiments have been performed at the stellarator TJ-II. Both the inward propagation of edge cooling pulses induced by the injection of nitrogen, and the outward propagation of heat pulses due to spontaneous spikes of the central temperature have been analysed. It has been found that the observed propagation is incompatible with diffusive transport models. Simultaneous inward and outward propagation eliminates an explanation in terms of a pinch. A numerical simulation with a resistive interchange turbulence model suggests that the observed propagation is related to the successive destabilizations of pressure gradient driven modes associated with rational surfaces.

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