Electrostatic turbulence intermittence driven by biasing in Texas Helimak

Autor(es)

Toufen, D. L. ^{[1, 2]} ; Pereira, F. A. C. ^[1] ; Guimaraes-Filho, Z. O. ^[1] ; Caldas, I. L. ^[1] ; Gentle, K. W. ^{[3, 4]}

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Phys, BR-05315970 Sao Paulo - Brazil

^[2] Fed Inst Educ Sci & Technol Sao Paulo IFSP, BR-07115000 Sao Paulo - Brazil

^[3] Univ Texas Austin, Dept Phys, Austin, TX 78712 - USA

^[4] Univ Texas Austin, Inst Fus Studies, Austin, TX 78712 - USA

• Tipo de documento: Artigo Científico
• Fonte: Physics of Plasmas; v. 21, n. 12 DEC 2014.
• Citações Web of Science: 5

Resumo

We investigate changes in the intermittent sequence of bursts in the electrostatic turbulence due to imposed positive bias voltage applied to control the plasma radial electric field in Texas Helimak {[}K. W. Gentle and H. He, Plasma Sci. Technol. 10, 284 (2008)]-a toroidal plasma device with a one-dimensional equilibrium, magnetic curvature, and shear. We identify the burst characteristics by analyzing ion saturation current fluctuations collected in a large set of Langmuir probes. The number of bursts increase with positive biasing, giving rise to a long tailed skewed turbulence probability distribution function. The burst shape does not change much with the applied bias voltage, while their vertical velocity increases monotonically. For high values of bias voltage, the bursts propagate mainly in the vertical direction which is perpendicular to the radial density gradient and the toroidal magnetic field. Moreover, in contrast with the bursts in tokamaks, the burst velocity agrees with the phase velocity of the overall turbulence in both vertical and radial directions. For a fixed bias voltage, the time interval between bursts and their amplitudes follows exponential distributions. Altogether, these burst characteristics indicate that their production can be modelled by a stochastic process. (C)2014 AIP Publishing LLC. (AU)

• Processo FAPESP: 12/22108-5 - Controle da turbulência em plasmas
• Beneficiário: Dennis Lozano Toufen
• Modalidade de apoio: Bolsas no Exterior - Pesquisa
• Processo FAPESP: 11/19296-1 - Dinâmica não linear
• Beneficiário: Iberê Luiz Caldas
• Modalidade de apoio: Auxílio à Pesquisa - Temático