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Studies of the pedestal structure and inter-ELM pedestal evolution in JET with the ITER-like wall
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0002-9546-4494
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2017 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 11, article id 116012Article in journal (Refereed) Published
Abstract [en]

The pedestal structure of type I ELMy H-modes has been analysed for JET with the ITER-like Wall (JET-ILW). The electron pressure pedestal width is independent of rho* and increases proportionally to root beta(pol,PED). Additional broadening of the width is observed, at constant beta(pol, PED), with increasing nu* and/ or neutral gas injection and the contribution of atomic physics effects in setting the pedestal width cannot as yet be ruled out. Neutral penetration alone does not determine the shape of the edge density profile in JET-ILW. The ratio of electron density to electron temperature scale lengths in the edge transport barrier region, eta(e), is of order 2-3 within experimental uncertainties. Existing understanding, represented in the stationary linear peeling-ballooning mode stability and the EPED pedestal structure models, is extended to the dynamic evolution between ELM crashes in JET-ILW, in order to test the assumptions underlying these two models. The inter-ELM temporal evolution of the pedestal structure in JET-ILW is not unique, but depends on discharge conditions, such as heating power and gas injection levels. The strong reduction in (pe,PED) with increasing D-2 gas injection at high power is primarily due to clamping of del T-e half way through the ELM cycle and is suggestive of turbulence limiting the T-e pedestal growth. The inter-ELM pedestal pressure evolution in JET-ILW is consistent with the EPED model assumptions at low gas rates and only at low beta at high gas rates. At higher beta and high gas rate the inter-ELM pedestal pressure evolution is qualitatively consistent with the kinetic ballooning mode (KBM) constraint but the peeling-ballooning (P-B) constraint is not satisfied and the ELM trigger mechanism remains as yet unexplained.

Place, publisher, year, edition, pages
EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England. [Maggi, C. F.; Saarelma, S.; Flanagan, J.; Lupelli, I.; Pamela, S.; Garzotti, L.; Lerche, E.; Rimini, F.] Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England. [Frassinetti, L.] KTH, Fus Plasma Phys, Assoc VR, SE-10044 Stockholm, Sweden. [Horvath, L.; Lunniss, A.; Wilson, H.; Leyland, M.] Univ York, York Plasma Inst, Dept Phys, York YO10 5DD, N Yorkshire, England. [Urano, H.] Natl Inst QST, Naka, Ibaraki 3110193, Japan. [Nunes, I.] Inst Super Tecn, Assoc IST, Av Rovisco Pais, P-1049001 Lisbon, Portugal.: Institute of Physics (IOP), 2017. Vol. 57, no 11, article id 116012
Keywords [en]
H-mode, pedestal structure, inter-ELM pedestal evolution, JET-ILW
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-243494DOI: 10.1088/1741-4326/aa7e8eISI: 000407218600001Scopus ID: 2-s2.0-85028473469OAI: oai:DiVA.org:kth-243494DiVA, id: diva2:1287146
Note

QC 20190208

Available from: 2019-02-08 Created: 2019-02-08 Last updated: 2019-02-08Bibliographically approved

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