Mahler<i>et al.</i>Respond

Mahler, G.; Forchel, A.; Laurich, B.; Schmid, W.

doi:10.1103/physrevlett.49.1744

Cited by 31 publications

(43 citation statements)

References 3 publications

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“…In view of the observed effects of biasing on radiated power, and the anticipated effects on plate heat loads, it is imperative to carry out biasing experiments with the megawatt level of additional heating at the lower hybrid frequency now available on TdeV. The added power is also likely to give an enhanced confinement mode (H mode [42]): although biasing has not strongly modified particle confinement and even less the energy confinement, it is possible that the edge electric field will promote or hinder the attainment of the H mode [39].…”

Section: Open Questionsmentioning

confidence: 99%

Improvements in recycling and impurity control obtained by divertor biasing

Terreault¹,

Stansfield²,

Lachambre³

et al. 1994

Nucl. Fusion

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Experiments in which the divertor plates are biased with respect to the grounded vacuum chamber were conducted in the Tokamak de Varennes, with ohmic discharges and boronized walls. A comprehensive set of diagnostics was used and those effects relating to plasma-surface interactions and their consequences, namely recycling and impurity production, are reported here. The main conclusion is that the bias voltage actively controls the balance between the particle fluxes to the walls and the diverters, with a weak influence on the confinement. The quantities associated with plasma surface interactions, i.e. the impurity influx, the plasma contamination and the global recycling coefficient, increase as a function of the voltage applied between the plates and the wall. Typically, the quantities of interest vary by a factor of two or more in the range from -240 to 290 V. The poloidal fluxes to the upper or lower divertor are enhanced by negative or positive biasing, respectively, in agreement with the sign of the E*B drift. For negative biasing the reduction in the wall flux and increase in the poloidal flux combine to improve greatly the divertor efficiency: the divertor pressure and the impurity retention time are increased by factors of up to 5 and 8, respectively. The above effects, together with the SOL density profiles and the biasing current-voltage characteristic, are consistent with a model in which the radial transport in the SOL is limited by the ion mobility; a mobility of 0.04 m2/V.s is found. Besides allowing active density and impurity control, it is suggested that biasing could facilitate the attainment of a radiative divertor by injection of well retained impurities in the divertor

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Section: Open Questionsmentioning

confidence: 99%

Improvements in recycling and impurity control obtained by divertor biasing

Terreault¹,

Stansfield²,

Lachambre³

et al. 1994

Nucl. Fusion

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“…Edge transport barriers are a key tool for enhancing the plasma confinement properties of magnetic-fusion devices, and therefore vital to the development of magnetic fusion as an alternative energy source. Soon after the formation of spontaneous transport barriers was first observed in the eighties [1], evidence was found that turbulence was being suppressed at the barrier location while a sheared electric field was formed [2], providing a first and essential clue to the physical mechanism to achieve the Low to High (L-H) confinement transition. After the release of the first physical model showing the possible role of radial electric fields in the development of plasma bifurcations [3] initial experimental verifications of the establishment of the mean radial electric field during edge plasma bifurcations were reported [4,5].…”

mentioning

confidence: 99%

Multi-scale physics mechanisms and spontaneous edge transport bifurcations in fusion plasmas

Hidalgo¹,

Pedrosa²,

Silva³

et al. 2009

Europhys. Lett.

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The magnitude of radial transport in magnetic confinement devices for controlled nuclear fusion suffers spontaneous bifurcations when specific system parameter values are exceeded. Here we show, for the first time, that the correlation length of the plasma potential becomes of the order of the machine size during the edge bifurcation itself, quite unlike the density fluctuations. The mechanism governing the development of this bifurcation, leading to the establishment of an edge transport barrier, is still one of the main scientific conundrums facing the magnetic fusion community after more than twenty years of intense research. The results presented here show the dominant role of long-range correlations when approaching the Low to High confinement edge transition in fusion plasmas. This is in line with the expectation that multi-scale interactions are a crucial ingredient of complex dynamics in many non-equilibrium systems.

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“…Edge localized modes (ELMs) [1] occur in tokamak plasmas operating in the high-energy confinement H-mode [2] regime and are important in the particle and power dynamics at the plasma edge. However, the distribution of ELM-generated heat and particle pulses on the surrounding vacuum vessel surfaces has become an increasingly important concern.…”

mentioning

confidence: 99%

The role of magnetic geometry on the poloidal distribution of ELM-induced peak particle flux at the divertor targets in DIII-D

et al. 2003

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Edge localized modes (ELMs) are commonly observed in high-energy confinement tokamak plasmas and are thought to be caused by magnetohydrodynamic instabilities driven by the steep pressure gradient and the current in the plasma edge region. Our data show that the divertor magnetic balance, i.e. the degree to which the plasma topology resembles a single-null or a double-null, strongly determines where ELM pulses driven by ballooning instabilities at the plasma edge are distributed to surrounding vacuum vessel surfaces. These data also support the conclusions drawn from the stability analysis that ELMs are generated almost entirely on the outboard side of the main plasma.

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Mahleret al.Respond

Cited by 31 publications

References 3 publications

Improvements in recycling and impurity control obtained by divertor biasing

Improvements in recycling and impurity control obtained by divertor biasing

Multi-scale physics mechanisms and spontaneous edge transport bifurcations in fusion plasmas

The role of magnetic geometry on the poloidal distribution of ELM-induced peak particle flux at the divertor targets in DIII-D

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