Kinetic simulations of ion temperature measurements from retarding field analyzers

Valsaque, Fabrice; Manfredi, Giovanni; Gunn, J.; Gauthier, E.

doi:10.1063/1.1463416

Cited by 40 publications

(53 citation statements)

References 31 publications

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“…[28,[47][48][49]). The model assumes that ions in the SOL are thermalized, so that the unperturbed 'SOL ion temperature' can be obtained from the I-V characteristics measured by both sides of a bidirectional RFA using the aforementioned calibration [29]. The present study distinguishes between the ion temperature in the filaments and that of the background plasma, showing that the first can be considerably higher …”

Section: Filament Ion Temperaturementioning

confidence: 99%

Ion temperature fluctuations in the ASDEX Upgrade scrape-off layer

Kočan

Gennrich

Kendl

et al. 2012

Plasma Phys. Control. Fusion

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Section: Filament Ion Temperaturementioning

confidence: 99%

Ion temperature fluctuations in the ASDEX Upgrade scrape-off layer

Kočan

Gennrich

Kendl

et al. 2012

Plasma Phys. Control. Fusion

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“…[27,28]). The asymmetry is theoretically understood and is associated with the perturbing effect of the probe on the plasma, combined with the plasma flow [29]. The analyzer towards which the flow is directed (here the LFS analyser, Sec.…”

Section: Hfs Satmentioning

confidence: 99%

“…The analyzer towards which the flow is directed (here the LFS analyser, Sec. 2.2) is expected to measure higher effective ion temperature [29]. The unperturbed ion temperature (namely that which would be observed in the absence of the probe) 80 measured by a simple LP and the heat flux density to the LP, monitored simultaneously by the fast IR camera.…”

Section: Hfs Satmentioning

confidence: 99%

First measurements of edge localized mode ion energies in the ASDEX Upgrade far scrape-off layer

Kočan

Herrmann

Müller

et al. 2011

Plasma Phys. Control. Fusion

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Abstract. Using the Retarding Field Analyser (RFA) technique, ion energies carried by ELM filaments have been measured for the first time in the far scrape-off layer (SOL) of the ASDEX Upgrade tokamak. Energies, ELM i E, exceeding 160 eV have been found, 5 -6 cm outside the separatrix, with a decay length of about 2 cm. The measured ELM particle ion temperature in the far SOL is in the range 80 50 − ≈ IntroductionThermal heat loads to the first wall during edge localized modes (ELMs) have been identified as one of the important issues for ITER burning plasma operation and determine the design of the ITER blanket module shaping and power handling capacity [1]. These heat loads scale with the energies carried by ELM ions to the first wall, which, in turn, depend on dissipation by parallel losses of the ELM energy to the divertor targets as the ELM particles travel across the SOL. Direct measurements of the ELM ion energies in the far SOL are, therefore, important in order to constrain the models of the ELM parallel transport in the SOL [2,3], which, in turn, increases the confidence in the model predictions towards ITER.Earlier measurements of the heat loads to the first wall in ASDEX Upgrade (AUG) revealed that up to~25% of the energy lost per ELM can be deposited on non-divertor components, indicating that ELM ions can carry relatively large fractions of the energy with which they are released into the SOL to the first wall [4,5,6]. These observations (also seen later on JET [7,8]), were consistent with increase by an order of magnitude of the tungsten influx from the outboard limiters in AUG during ELMs compared to inter-ELM periods [9]. Energetic ELM ions (impact energies exceeding 400 eV) in the far SOL (typically 2-3 characteristic SOL power widths outside the separatrix) were measured directly for the first time in JET [10] (and more recently in MAST [11]) using a Retarding Field

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“…, HFS/LFS indicating respectively the analyzer intercepting magnetic field lines coming from the high field side or the low field side (typically, each side of the RFA measures different i T , which, as shown in [53], is associated with the perturbing effect of the probe combined with the parallel plasma flows , respectively. The total (ion and electron) heat transmission coefficient γ is calculated as [56]: …”

mentioning

confidence: 99%

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

Kočan¹,

Gunn

2010

Plasma Phys. Control. Fusion

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In the Tore Supra tokamak, the scrape-off layer profiles of discharges limited either on the inboard or on the outboard side are compared. Inboard-limited discharges are characterized by substantially longer SOL e-folding lengths of ion and electron temperatures and electron density measured near the top of the plasma, providing strong evidence that the ion and electron energy transport across the SOL is enhanced on the outboard side, similar to the particle transport. The parallel heat flux density extrapolated to the last closed flux surface is found to be inversely proportional to its e-folding length in the SOL. The outboard limiters thus receive higher and more peaked heat loads than the inboard limiters. These results are important for the optimization of the plasma start-up scenario and design of the first wall in ITER.PACS 52.25.Fi, 52.25.Xz, 52.35.Ra, 52.55.Fa, 52.70.Ds IntroductionIn tokamaks, the intermittent expulsion of magnetic-field-aligned plasma filaments from the last closed flux surface (LCFS) is responsible for a large fraction of the effective radial transport to the wall [1][2][3][4][5][6]. Filament propagation appears to be governed by a ballooning-type instability in the unfavourable magnetic curvature region on the low field side. As the filaments propagate outward, they also expand freely along the magnetic field lines, driving pressure-driven field-direction-independent parallel flows. Mach probe measurements in many divertor tokamaks (e.g. [7] and references therein) show flow patterns consistent with this model (i.e. stagnant flow poloidally approximately halfway between the outer midplane and the X-point), in which the filaments can be seen as an important particle source in the scrape-off layer (SOL). Similar observations in limiter tokamaks [8][9][10][11][12] prove that enhanced radial particle transport on the outboard side of the plasma is a universal phenomenon, independent of the presence of an X-point divertor. The enhancement of the radial particle transport on the outboard side of the limiter plasmas was confirmed by the 3D fluid turbulence code TOKAM-3D [13]. When the plasma contact point is on the inboard limiters, the filaments propagate freely out to the wall, filling all the available volume outside the LCFS and leading to a broad SOL with nearly flat density profiles. On the other hand, it was demonstrated [12] that outboard modular limiters suppress the radial particle transport when they are near the LCFS, leading to a very thin SOL. It is probable [8] that the limiters act as simple mechanical barriers that intercept the parallel particle flux in the region in which the enhanced radial convection.

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Kinetic simulations of ion temperature measurements from retarding field analyzers

Cited by 40 publications

References 31 publications

Ion temperature fluctuations in the ASDEX Upgrade scrape-off layer

Ion temperature fluctuations in the ASDEX Upgrade scrape-off layer

First measurements of edge localized mode ion energies in the ASDEX Upgrade far scrape-off layer

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

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