Measurements of the parallel ion velocity distribution at the plasma–sheath interface

Kočan, M.; Gunn, J.; Fuchs, V.; Müller, Hans

doi:10.1016/j.jnucmat.2013.01.103

Cited by 3 publications

(3 citation statements)

References 16 publications

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“…5 for the calculation of the sputtering yields. For finite secondary electron emission δ se ̸ = 0, however, the sheath potential can be reduced significantly as indicated by measurements in different tokamaks [20][21][22]. This reduction of the sheath potential decreases the acceleration of the ions in the sheath and therefore reduces the impact of the impurities for the erosion process (see Fig.…”

Section: Erosion With 1% Impurity Concentration and Reduced Sheathmentioning

confidence: 95%

Filament transport, warm ions and erosion in ASDEX Upgrade L-modes

Birkenmeier¹,

Mänz²,

Carralero³

et al. 2015

Nucl. Fusion

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The dynamics of blob filaments are investigated in the scrape-off layer of ASDEX Upgrade by means of lithium beam emission spectroscopy. A comparison of the measurements in L-mode with a recently developed analytical blob model based on a drift-interchange-Alfvén fluid model indicates an influence of a finite ion temperature on the blob dynamics which has typically been neglected in other blob models. The blob dynamics agree well with the sheath-connected regime at lower plasma densities, and inertial effects play only a minor role. At higher densities, a transition into another regime with large blob amplitudes and increased transport is found. This points to a prominent role of blob transport at higher Greenwald fractions. On the basis of the measured blob properties, the erosion on plasma facing components is estimated. For pure deuterium plasmas, the high ion temperatures of blobs lead to a dominant erosion induced by blobs. However, if an impurity concentration of 1% is taken into account, the blob-induced erosion plays a minor role and background plasma parameters determine the total gross erosion.

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Section: Erosion With 1% Impurity Concentration and Reduced Sheathmentioning

confidence: 95%

Filament transport, warm ions and erosion in ASDEX Upgrade L-modes

Birkenmeier¹,

Mänz²,

Carralero³

et al. 2015

Nucl. Fusion

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“…The resulting E × B drift disperses the ions along an array of collectors. The spatial distribution of ions along the collectors is a function of the parallel ion velocity, v , so that the parallel ion velocity distribution at the probe surface, f i (v ), as well as T i can be inferred from the collector currents (recently, a least-squares regularization method was used to extract f i (v ) from the time-averaged data measured by the RFA in the AUG L-mode plasma [33], which can be later compared with the E × B analyser measurements).…”

Section: Ion Energies In Turbulent Plasma Filamentsmentioning

confidence: 99%

Intermittent transport across the scrape-off layer: latest results from ASDEX Upgrade

et al. 2013

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Abstract.We report the latest results of turbulence and transport studies in the ASDEX Upgrade scrapeoff layer (SOL). Dissimilarity between the plasma and the floating potential fluctuations is studied experimentally and by gyrofluid simulations. Measurements by a retarding field analyzer reveal that both, ELM and turbulent filaments convey hot ions over large radial distances in the SOL. The measured far SOL ELM ion temperature increases with the ELM energy, consistent with earlier observations that large ELMs deposit a large fraction of their energy outside the divertor. In the SOL, the ELM suppression by magnetic perturbations (MPs) results into lower ELM ion energy in the far SOL. At the same time, large filaments of ion saturation current are replaced by more continuous bursts. Splitting of the divertor strike zones observed by the infrared imaging in H-mode with MPs agree with predictions from the EMC3-Eirene simulations. This suggests that the 'lobe' structures due to perturbation fields observed near the X-point are not significantly affected by plasma screening, and can be described by a vacuum approach, as in the EMC3-Eirene. Finally, some effects of the MPs on the L-mode SOL are addressed.

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“…There has been a small number of experimental works claiming that electron reflection from technical metal surfaces at low incident energies can be significantly enhanced, even reach 100% at the limit of zero incident energy [3]. This argument has been iterated within the fusion community in order to explain a number of experimental observations [4][5][6][7]. However, it not only contra-dicts concrete experimental evidence for clean metal surfaces but also lacks a sound theoretical basis.…”

mentioning

confidence: 99%

Low energy electron reflection from tungsten surfaces

Tolias¹

2016

Preprint

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Measurements of the parallel ion velocity distribution at the plasma–sheath interface

Cited by 3 publications

References 16 publications

Filament transport, warm ions and erosion in ASDEX Upgrade L-modes

Filament transport, warm ions and erosion in ASDEX Upgrade L-modes

Intermittent transport across the scrape-off layer: latest results from ASDEX Upgrade

Low energy electron reflection from tungsten surfaces

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