TY - JOUR
T1 - Turbulence, flows and edge localized mode (ELM) dynamics in limiter H-mode plasmas in TEXTOR
JF - Plasma Physics and Controlled Fusion
Y1 - 2010
A1 - Soldatov, S.
A1 - Kramer-Flecken, A.
A1 - Kantor, M.
A1 - Unterberg, B.
A1 - Sun, Y.
A1 - Van Oost, G.
A1 - Reiter, D.
KW - ALCATOR C-MOD
KW - ASDEX UPGRADE TOKAMAK
KW - DENSITY-FLUCTUATIONS
KW - DIII-D
KW - ergodic divertor
KW - I ELMS
KW - microwave
KW - POWER THRESHOLD
KW - RADIAL ELECTRIC-FIELD
KW - REFLECTOMETRY
KW - REFLECTOMETRY MEASUREMENTS
KW - TOKAMAK
AB - The turbulence, plasma flow and edge localized mode (ELM) dynamics in the limiter H-mode TEXTOR plasmas are investigated. Properties of both ambient turbulence within 0 < k(perpendicular to) < 4.2 cm(-1) and coherent modes are studied on the ELM time scale in detail. The turbulence level near the pedestal is shown to evolve several times with the period of ELMs. Within the inter-ELM period the 'silent stage' is found which is characterized by an extremely low(below that for Ohmic plasmas) turbulence level and a phase growth in the reflectometry signal. The silent stage is associated with the quasi-steady state when the pedestal is formed and confinement is improved between two successive ELMs. Quasi-coherent density oscillations near the pedestal region with m approximate to 3, 5, 16 and 38 are measured with correlation reflectometry. Low-m modes are found to reveal the signatures of precursor mode. At first, the radial structure of the rotation shear and radial electric field E-r in limiter H-mode in TEXTOR is presented. The characteristic negative electric field well with the sharp gradient del E-r approximate to 250 V cm(-2) at approximate to 2 cm inside separatrix is resolved. The E-r x B rotation profile defines both the resulting plasma rotation in the electron diamagnetic drift direction and a significant rotation shear near the separatrix which exceeds the decorrelation rate of ambient turbulence by several times.
VL - 52
SN - 0741-3335
UR - ://000279709700001
N1 - ISI Document Delivery No.: 623AUTimes Cited: 0Cited Reference Count: 71
U5 - c885c433ded4d7f48ad7c43a741939b7
ER -
TY - JOUR
T1 - Study of type III ELMs in JET
JF - Plasma Physics and Controlled Fusion
Y1 - 2004
A1 - Sartori, R.
A1 - Saibene, G.
A1 - Horton, L. D.
A1 - Becoulet, M.
A1 - Budny, R.
A1 - Borba, D.
A1 - Chankin, A.
A1 - Conway, G. D.
A1 - Cordey, G.
A1 - McDonald, D.
A1 - Guenther, K.
A1 - von Hellermann, M. G.
A1 - Igithkanov, Y.
A1 - Loarte, A.
A1 - Lomas, P. J.
A1 - Pogutse, O.
A1 - Rapp, J.
KW - BOUNDARIES
KW - CONFINEMENT
KW - divertor
KW - EDGE LOCALIZED MODES
KW - H-MODES
KW - HIGH-DENSITY
KW - OPERATION
KW - PERFORMANCE
KW - PHYSICS
KW - POWER THRESHOLD
AB - This paper presents the results of JET experiments aimed at studying the operational space of plasmas with a Type III ELMy edge, in terms of both local and global plasma parameters. In JET, the Type III ELMy regime has a wide operational space in the pedestal n(e)-T-e diagram, and Type III ELMs are observed in standard ELMy H-modes as well as in plasmas with an internal transport barrier (ITB). The transition from an H-mode with Type III ELMs to a steady state Type I ELMy H-mode requires a minimum loss power, P-TypeI-P-TypeI decreases with increasing plasma triangularity. In the pedestal n(e)-T-e diagram, the critical pedestal temperature for the transition to Type I ELMs is found to be inversely proportional to the pedestal density (T-crit proportional to 1/n) at a low density. In contrast, at a high density, T-crit, does not depend strongly on density. In-the density range where T-crit proportional to 1/n, the critical power required for the transition to Type I ELMs decreases with increasing density. Experimental results are presented suggesting a common mechanism for Type III ELMs at low and high collisionality. A single model for the critical temperature for the transition from Type III to Type I ELMs, based on the resistive interchange instability with magnetic flutter, fits well the density and toroidal field dependence of the JET experimental data. On the other hand, this model fails to describe the variation of the Type III n(e)-T-e operational space with isotopic mass and q(95). Other results are instead suggestive of a different physics for Type III ELMs. At low collisionality, plasma current ramp experiments indicate a role of the edge current in determining the transition from Type III to Type I ELMs, while at high collisionality, a model based on resistive ballooning instability well reproduces, in term of a critical density, the experimentally observed q(95) dependence of the transition from Type I to Type III ELMs. Experimental evidence common to Type III ELMs in standard ELMy H-modes and in plasmas with ITBs indicates that they are driven by the same instability.
VL - 46
SN - 0741-3335
UR - ://000221752400002
N1 - ISI Document Delivery No.: 825JH
U1 - Fusion Physics
U2 - Instrumentation development
U5 - 9b68933292075b57fba7b19e2d18cd5a
ER -