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Your search keyword '"Ruchko, L. F."' showing total 26 results
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26 results on '"Ruchko, L. F."'

2. Report on recent results obtained in TCABR

Author

Galvão, R M O, primary, Amador, C H S, additional, Baquero, W A H, additional, Borges, F, additional, Caldas, I L, additional, Cuevas, N A M, additional, Duarte, V N, additional, Elfimov, A G, additional, Elizondo, J I, additional, Fonseca, A M M, additional, Germano, T M, additional, Grenfell, G G, additional, Guimarães-Filho, Z O, additional, Jeronimo, J L, additional, Kuznetsov, Yu K, additional, Manrique, M A M, additional, Nascimento, I C, additional, Pires, C J A, additional, Puglia, P G P, additional, Reis, A P, additional, Ronchi, G, additional, Ruchko, L F, additional, de Sá, W P, additional, Sgalla, R J F, additional, Sanada, E K, additional, Severo, J H F, additional, Theodoro, V C, additional, and Toufen, D L, additional

Published
2015
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6. Role of trapped and circulating particles in inducing current drive and radial electric field by Alfven waves in tokamaks

Author

Tsypin, V. S., Galvao, R. M. O., Nascimento, I. C., Tendler, Michael, Severo, J. H. F., Ruchko, L. F., Tsypin, V. S., Galvao, R. M. O., Nascimento, I. C., Tendler, Michael, Severo, J. H. F., and Ruchko, L. F.

Abstract

Absorption by trapped particles is supposed to seriously hinder current drive by Alfven waves. However, it is shown in this paper that the same effect is rather beneficial for the emergence of the radial electric field induced by these waves, which is important for creating and maintaining transport barriers in tokamaks., QC 20100525

Published
2002
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7. Externally driven global Alfvén eigenmodes applied for effective mass number measurement on TCABR.

Author

Puglia, P. G. P. P., Elfimov, A. G., Ruchko, L. F., Galvão, R. M. O., Guimarães-Filho, Z., and Ronchi, G.

Subjects
EFFECTIVE mass (Physics), NUMBER theory, METAL oxide semiconductor field-effect transistors, PLASMA frequencies, TOROIDAL plasma
Abstract

The excitation and detection of Global Alfvén Eigenmodes on TCABR for diagnostic purposes are presented. The modes can be excited with one or two in-vessel antennae, with up to 15A of current in each, in the frequency range from 2 to 4 MHz. This scheme allows the estimation of the effective mass number at the plasma center, which value is affected by impurity concentration in the core. An amplifier based on MOSFETs is used to excite the waves driven by low power, in order to not change the basic plasma parameters. The variation of the GAE with density is verified and the location of the mode resonance at the plasma center is confirmed by the sawtooth beating, so that the correspondingly beating phase inversion improves the precision on the resonant condition determination. The toroidal parity of the modes N=1,2 is determined by use of two opposite located antennae with different phase of the RF current. Knowledge of toroidal mode number is important as it identifies GAE location and defines the estimated effective mass value. The estimated value for Aeff is ~1.4-1.5, corresponding to 5-7% of carbon impurity concentration. The measured value of Aeff is used to estimate Zeff, which is compared to older TCA experiments and the value obtained by the Spitzer conductivity. [ABSTRACT FROM AUTHOR]

Published
2014
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8. Density Limit in TCABR Plasmas With Alfvén Wave Heating

Author

Ribeiro, C., primary, Bellintani, V., additional, Elfimov, A. G., additional, Elizondo, J. I., additional, Fagundes, A. N., additional, Galvão, R. M. O., additional, Kuznetsov, Yu K., additional, Nascimento, I. C., additional, Ozono, E. M., additional, Ruchko, L. F., additional, de Sá, W. P., additional, Sanada, E. K., additional, and Usuriaga, O. C., additional

Published
2006
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9. Overview of Recent Results of TCABR

Author

Bellintani, V., primary, Elfimov, A. G., additional, Elizondo, J. I., additional, Fagundes, A. N., additional, Fonseca, A. M. M., additional, Galvão, R. M. O., additional, Guidolin, L., additional, Kuznetsov, Yu. K., additional, Lerche, E. A., additional, Machida, M., additional, Mariz, C., additional, Nascimento, I. C., additional, Ribeiro, C., additional, Ruchko, L. F., additional, de Sá, W. P., additional, Sanada, E. K., additional, Severo, J. H. F., additional, da Silva, R. P., additional, Tsypin, V., additional, Usuriaga, O. C., additional, and Vannucci, A., additional

Published
2006
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10. Recombinative plasma in electron runaway discharge

Author

Kuznetsov, Yu. K., primary, Galvão, R. M. O., additional, Usuriaga, O. C., additional, Krasheninnikov, S. I., additional, Soboleva, T. K., additional, Tsypin, V. S., additional, Fonseca, A. M. M., additional, Ruchko, L. F., additional, and Sanada, E. K., additional

Published
2005
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13. Identification of the Alfvén wave resonances in the TCABR tokamak by the microwave reflectometry

Author

Ruchko, L. F., primary, Galvão, R. M. O., additional, Lerche, E. A., additional, Elfimov, A. G., additional, Bellintani Jr, V., additional, Elizondo, J. I., additional, Fagundes, A. N., additional, Fonseca, A. M. M., additional, Kuznetsov, Yu. K., additional, Nascimento, I. C., additional, Sá, W. P. de, additional, Sanada, E., additional, Silva, R. P. da, additional, and Valencia, R., additional

Published
2004
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16. Application of microwave reflectometry to register Alfvén wave resonances in the TCABR tokamak

Author

Ruchko, L. F., primary, Valencia, R., additional, Galvão, R. M. O., additional, Lerche, E. A., additional, Elfimov, A. G., additional, Bellintani, V., additional, Elizondo, J. I., additional, Fagundes, A. N., additional, Fonseca, A. M. M., additional, Kuznetsov, Yu. K., additional, Nascimento, I. C., additional, de Sá, W. P., additional, Sanada, E., additional, and da Silva, R. P., additional

Published
2004
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18. Recent Results of Alfvén Wave Studies in TCABR.

Author

Lerche, E. A., Ruchko, L. F., Ozono, E. M., Galvão, R. M. O., Elfimov, A. G., Fonseca, A. M. M., and da Silva, R. P.

Subjects
*TOKAMAKS, *PINCH effect (Physics), *THERMONUCLEAR fuels, *NUCLEAR fuels
Abstract

The results on comparative studies of Alfvén wave plasma heating by two different antenna types in TCABR are presented. Emphasis is placed on the excited wave spectra and parasitic coupling with the edge plasma. The antenna modules have two groups of RF current-carrying straps separated by a toroidal angle of approximately 22°. In type I antenna, each group consists of two circular loops that are cut in two half-turn windings. The feeders of each loop pair are rotated 90° in the poloidal direction with respect to each other, to decrease the mutual coupling between them and make it possible to excite single helicity plasma modes (M=+1 or M=-1). In type II antenna, each group consists of two poloidal straps located at the low-magnetic-field side of the vacuum chamber. The poloidal extension of each strap is around 90° and the angle between straps is also of the same value. In both antenna types, the straps have side protectors of boron nitride. Initial experiments indicate that the parasitic interaction with the edge plasma is quite different for the two antennae. Also the first type has larger self-inductance, making it more difficult to deliver high currents to the antenna without increasing the dynamic polarization voltage up to breakdown limits. Results on the excited spectrum and floating potential at the plasma edge are presented. [ABSTRACT FROM AUTHOR]

Published
2003

19. Alfvén wave heating and runaway discharges maintained by the avalanche effect in TCABR

Author

Galvão, R M O, primary, Bellintani, V, additional, Bengtson, R D, additional, Elfimov, A G, additional, Elizondo, J I, additional, Fagundes, A N, additional, Ferreira, A A, additional, Fonseca, A M M, additional, Kuznetsov, Yu K, additional, Lerche, E A, additional, Nascimento, I C, additional, Ruchko, L F, additional, Sá, W P de, additional, Saettone, E A, additional, Sanada, E, additional, Severo, J H F, additional, Silva, R P da, additional, Tsypin, V S, additional, Usuriaga, O C, additional, and Vannucci, A, additional

Published
2001
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20. New regime of runaway discharges in tokamaks

Author

Galvão, R M O, primary, Kuznetsov, Yu K, additional, Nascimento, I C, additional, Sanada, E, additional, Campos, D O, additional, Elfimov, A G, additional, Elizondo, J I, additional, Fagundes, A N, additional, Ferreira, A A, additional, Fonseca, A M M, additional, Lerche, E A, additional, Lopez, R, additional, Ruchko, L F, additional, Sá, W P de, additional, Saettone, E A, additional, Severo, J H F, additional, Silva, R P da, additional, Tsypin, V S, additional, Valencia, R, additional, and Vannucci, A, additional

Published
2001
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21. Preliminary results on Alfve´n wave system in the TCABR tokamak.

Author

Lerche, E. A., Ozono, E. M., Ruchko, L. F., Galva˜o, R. M. O., Elfimov, A. G., Tsypin, V., Sanada, E., Sa´, W. P., Nascimento, I. C., Kuznetsov, Yu. K., Fagundes, A. N., Vannucci, A., Campos, D., Elizondo, J. I., Severo, J. H. F., Saettone, E. A. S., Bellintani, V., and Ferreira, A. A.

Subjects
TOKAMAKS, MAGNETOHYDRODYNAMIC waves, PLASMA gases
Abstract

A brief review of the Alfvén Wave Excitation System (AWES) designed for the TCABR tokamak and the first experimental results on RF plasma heating are presented. One of four antenna modules has been completely installed in the vacuum chamber and the initial experiments were carried out in the low power regime using the four-phase RF generator. The main objectives were the antenna tuning according to the typical plasma parameters of TCABR and the evaluation of the antenna parasitic loading, as well as the calibration of the RF diagnostic tools in real discharge conditions. The first results have been obtained with standard diagnostics and with the RF signals measured using high sampling rate digital oscilloscopes. They showed that daily antenna cleaning and correct wave helicity excitation reduce significantly the parasitic loading and are crucial for efficient plasma coupling. [ABSTRACT FROM AUTHOR]

Published
2001

23. Long-distance correlations in TCABR8 biasing experiments.

Author

Kuznetsov, Yu.K., Nascimento, I. C., Silva, C., Figueiredo, H., Guimar'aes-Filho, Z. O., Caldas, I. L., Galv'ao, R. M. O., Severo, J. H. F., Toufen, D. L., Ruchko, L. F., Elfimov, A. G., Elizondo, J. I., de S'a, W. P., Usuriaga, O. C., Sanada, E., Melnikov, A. V., Gryaznevich, M. P., Alonso, M. Peres, Reis, A. P., and Machida, M.

Subjects
PLASMA gases, STATISTICAL correlation, FLUCTUATIONS (Physics), LANGMUIR probes, RADIO frequency, TOKAMAKS
Abstract

Long-distance correlations (LDCs) of plasma potential fluctuations in the plasma edge have been investigated in the TCABR tokamak in the regime of edge biasing H-mode using an array of multi-pin Langmuir probes. This activity was carried out as part of the scientific programme of the 4th IAEA Joint Experiment (2009). The experimental data confirm the effect of amplification of LDCs in potential fluctuations during biasing recently observed in stellarators and tokamaks. For long toroidal distances between probes, the cross-spectrum is concentrated at low frequencies f < 60 kHz with peaks at f < 5 kHz, f = 13-15 kHz and f ∼40 kHz and low wave numbers with a maximum at k = 0. The effects of MHD activity on the LDCs in potential fluctuation are investigated. [ABSTRACT FROM AUTHOR]

Published
2012
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25. The analysis of Alfvén wave antenna implementation in the ETE spherical tokamak

Author

Ruchko,L. F. and Galvão,R. M. O.

Abstract

The preliminary design study of the Alfvén wave system for the ETE spherical tokamak is presented. The main objective of the proposed RF system is generation of travelling Alfvén waves, which can be used for the study of the non-inductive current drive and the plasma heating in a wide range of operational regimes, which are specific for tokamaks with small aspect ratio R/a 1.2 - 1.5. The antenna system consists of four modules, which are separated by 90º in toroidal direction. Each module has two sets of RF current carrying poloidal straps that are positioned symmetrically in relation to the equatorial plane of the vacuum chamber at the poloidal coordinates ±45º. The poloidal extension of each strap is approximately 90º. The excited mode numbers can be controlled by the phasing of the feeding RF current. In the basic regime of operation, the straps in the same toroidal cross-sections are fed by the RF currents with (0, ±pi/2) phasing so that they can excite travelling modes M = ±1, N = ±1. In order to decrease the periphery RF power deposition and to improve the selectivity of the Alfvén mode excitation, the inclination of the antenna straps in toroidal direction can be adjusted in the range of angles ±30º. The dependence of the antenna efficiency on the antenna orientation is studied numerically in the frame of 1-D MHD model.

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