Ion energies and currents of type I and mitigated ELMs in the ASDEX Upgrade far scrape-off layer

Kočan, M.; Allan, S.; Carpentier-Chouchana, S.; Marné, P. de; Elmore, S.; Franke, T.; Gunn, J.; Herrmann, A.; Kirk, A.; Kubič, M.; Lunt, T.; Müller, Hans; Pitts, R.A.; Rohde, V.

doi:10.1088/0029-5515/52/2/023016

Cited by 23 publications

(35 citation statements)

References 54 publications

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“…Illustrative results discussed here appear in more detail in Ref. [25]. Figure 9 shows typical time traces of j sat and I c measured by the RFA in two similar type I ELMs at Δr sep = 35 mm.…”

Section: Far Sol Elm Ion Energiesmentioning

confidence: 93%

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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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Section: Far Sol Elm Ion Energiesmentioning

confidence: 93%

“…[21]. Despite of its relative simplicity, the model was previously successful in reproducing a variety of experimental observations in AUG and JET [19,[21][22][23][24][25]. Additionally, in Ref.…”

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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“…Since RFEA probes rely on the assumption that the ion distribution measured is Maxwellian, measurements of ELMs can prove difficult. At the target, measurements of ELMs have been attempted by both the SST, as used on AUG [4] and MAST for Lmode filaments [17] and previous ELM measurements on MAST [17], and the FST. Here, two similar sets of type III ELMs are used to compare the two methods.…”

Section: Validation Of Elm Measurements By Rfeamentioning

confidence: 99%

“…Previous measurements made in JET [2], ASDEX Upgrade (AUG) [3] [4]and MAST [5] with retarding field energy analysers (RFEA) have shown that ELMs can carry significant amounts of energetic ions into the far SOL at the mid-plane. For tokamaks with close fitting vessel walls, such as ITER, this can be a significant problem since high thermal loading to first wall and divertor materials may cause damage.…”

Section: Introductionmentioning

confidence: 99%

Scrape-off layer ion temperature measurements at the divertor target during type III ELMs in MAST measured by RFEA

Elmore

Allan

Fishpool

et al. 2015

Journal of Nuclear Materials

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In future nuclear fusion reactors high heat load events, such as edge-localised modes (ELMs), can potentially damage divertor materials and release impurities into the main plasma, limiting plasma performance. The most difficult to handle are type I ELMs since they carry the largest fraction of energy from the plasma and therefore deposit the largest heat flux at the target and on first wall materials. Knowing the temperature of the ions released from ELM events is important since it determines the potential sputtering they would cause from plasma facing materials. To make measurements of T i by retarding field energy analyser (RFEA) during type I ELMs a new operational technique has been used to allow faster measurements to be made; this is called the fast swept technique (FST). The FST method allows measurements to be made within the time of the ELM event which has previously not been possible with T i measurements. This new technique has been validated by comparing it with a slower average measurement previously used to make ion temperature measurements of ELMs. Presented here are the first T i measurements during Type I ELMs made at a tokamak divertor. Temperatures as high as 20 eV are measured more than 15 cm from the peak heat flux of an ELM, in a region where no inter-ELM current is measured by the RFEA; showing that ELM events cause hot ions to reach the divertor target far into the scrape off layer. Fast camera imaging has been used to investigate the type of ELM filaments that have been measured by the divertor RFEA. It is postulated that most of the ion temperatures measured in type I ELMs are from secondary ELM filaments which have not been previously identified in MAST plasmas.2

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“…The model was previously employed to study the transport of ELM filaments in JET (e.g. [14,26]) and AUG ( [17,41]). Once the initial filament temperatures and density are specified, their time evolution due to parallel transport to the nearest surface can be calculated.…”

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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Ion energies and currents of type I and mitigated ELMs in the ASDEX Upgrade far scrape-off layer

Abstract: Abstract. New measurements of ion energies and currents in

Cited by 23 publications

References 54 publications

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

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

Scrape-off layer ion temperature measurements at the divertor target during type III ELMs in MAST measured by RFEA

Ion temperature fluctuations in the ASDEX Upgrade scrape-off layer

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