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Scaling of the frequencies of the type one edge localized modes and their effect on the tungsten source in JET ITER-like wall
CEA IRFM, F-13108 St Paul Les Durance, France.;IRFM, CEA, F-13108 St Paul Les Durance, France..
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
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Number of Authors: 11082016 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 12, article id 125014Article in journal (Refereed) Published
Abstract [en]

A database of 250 pulses taken randomly during the experimental campaigns of JET with the ITER-like wall (ILW) is used to study the frequency dependences of the type I edge localized modes (ELM). A scaling of the ELM frequency is presented as a function of the pedestal density drop dN(ped) and a very simple model to interpret this scaling is discussed. In this model, the frequency of the ELMs is governed by the time needed by the neutral flux to refill the density of the pedestal. The filling rate is the result of a small imbalance between the neutral flux filling the pedestal and the outward flux that expels the particles to the SOL. The ELM frequency can be governed by such a mechanism if the recovery time of the temperature of the pedestal in JET occurs before or at the same time as the one of the density. This is observed to be the case. An effect of the fuelling is measured when the number of injected particles is less than 1 x 10(22) particles s(-1). In that case an increase of the inter-ELM time is observed which is related to the slower recovery of the density pedestal. Additionally, a scaling is found for the source of tungsten during the ELMs. The number of tungsten atoms eroded by the ELMs per second is proportional to dNped multiplied by the ELM frequency. This is possible only if the tungsten sputtering yield is independent of the energy of the impinging particle hitting the divertor. This result is in agreement with Guillemault et al (2015 Plasma Phys. Control. Fusion 57 085006) and is compatible with the D+ ions hitting the divertor having energies above 2 keV. Finally, by plotting the W-content/W-source ratio during ELM crash, a global decreasing behaviour with the ELM frequency is found. However at frequencies below 40 Hz a scatter towards upper values is found. This scatter is found to correlate with the gas injection level. In a narrow ELM frequency band around 20 Hz, it is found that both the ratio W-content/W-source and W-source decrease with the gas injection.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD , 2016. Vol. 58, no 12, article id 125014
Keywords [en]
tokamak, ELMs, tungsten
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-270600DOI: 10.1088/0741-3335/58/12/125014ISI: 000387892600002Scopus ID: 2-s2.0-84997831853OAI: oai:DiVA.org:kth-270600DiVA, id: diva2:1413509
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QC 20200310

Available from: 2020-03-10 Created: 2020-03-10 Last updated: 2020-03-10Bibliographically approved

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Bergsåker, HenricBykov, IgorElevant, ThomasFrassinetti, LorenzoGarcia-Carrasco, AlvaroHellsten, TorbjörnIvanova, DaryaJohnson, ThomasMenmuir, SheenaPetersson, PerRachlew, ElisabethRubel, MarekStröm, PetterTholerus, EmmiWeckmann, Armin
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