Characterization of small ELM experiments in highly shaped single null and quasi-double-null plasmas in JET

Saibene, G.; Lomas, P. J.; Sartori, R.; Loarte, A.; Stöber, J.; Andrew, Y.; Arshad, S.; Conway, G. D.; Luna, E. de la; Günther, K.; Ingesson, L. C.; Kempenaars, M.; Korotkov, A.; Koslowski, H. R.; Lönnroth, J.; McDonald, D. C.; Meigs, A.; Monier‐Garbet, P.; Parail, V.; Perez, C. P.; Rimini, F.; Sharapov, S. E.; Thomas, Paul R.

doi:10.1088/0029-5515/45/5/001

Cited by 84 publications

(116 citation statements)

References 29 publications

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“…1(f) [10]. In recent experiments on JET and AUG, grassy-like ELMs were also observed following the grassy ELM prescription with high β p plasmas (β p >1.7) at high q 95 (q 95 ∼7) and high triangularity (δ>0.4) [11,12]. As can be seen in Fig.…”

Section: Grassy Elm Regimementioning

confidence: 81%

“…So far, a QDN configuration is required both for type II ELMs and for grassy ELMs in AUG [7,12]. In JET, type II ELM does not require QDN configuration, while grassy ELM has been observed in QDN configuration so far [11]. Grassy ELMs in JT-60U have often been observed for lower single null (LSN) operation without a second separatrix and type V ELM in NSTX also requires LSN configuration.…”

Section: Discussion and Summarymentioning

confidence: 99%

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Pedestal conditions for small ELM regimes in tokamaks

Oyama¹,

Gohil²,

Horton³

et al. 2006

Plasma Phys. Control. Fusion

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104

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Abstract. Several small/no ELM regimes such as EDA, grassy ELM, HRS, QHmode, type II and V ELMs with good confinement properties have been obtained in Alcator C-Mod, ASDEX-Upgrade, DIII-D, JET, JFT-2M, JT-60U and NSTX. All these regimes show considerable reduction of instantaneous ELM heat load onto divertor target plates in contrast to conventional type I ELM, and ELM energy losses are evaluated as less than 5% of the pedestal stored energy. These small/no ELM regimes are summarized and widely categorized by their pedestal conditions in terms of the operational space in non-dimensional pedestal parameters and requirement of plasma shape/configuration. The characteristics of edge fluctuations and activities of ideal MHD stability leading to small/no ELMs are also summarized.

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Section: Grassy Elm Regimementioning

confidence: 81%

Section: Discussion and Summarymentioning

confidence: 99%

Pedestal conditions for small ELM regimes in tokamaks

Oyama¹,

Gohil²,

Horton³

et al. 2006

Plasma Phys. Control. Fusion

Self Cite

104

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“…Furthermore H 98 and W th decrease with increasing deuterium fuelling for JET-ILW plasmas unlike the JET-C plasmas. As reported in [Leyland 2013] the JET-C plasmas maintain and even improve overall performance (H 98 and W th ) with increasing deuterium fuelling due to a transition from pure Type I ELMs to the so called mixed Type I/II ELMs [Saibene 2002, Saibene 2005]. …”

Section: Plasma Performancementioning

confidence: 83%

“…The plasma performance was not only maintained but even improved with increased fuelling up to a density pedestal normalised to the Greenwald density (n e,ped /n GW )  1. This improvement in performance was attributed to an increase in pedestal stored energy which coincided with a transition from pure Type I ELMs to mixed Type I/II ELMs [Saibene 2002, Saibene 2005, Giroud 2012. A key result was that the pre-ELM electron temperature and density pedestal width increased from low to high deuterium fuelling.…”

Section: Introductionmentioning

confidence: 97%

The H-mode pedestal structure and its role on confinement in JET with a carbon and metal wall

Leyland

Beurskens

Frassinetti³

et al. 2014

Nucl. Fusion

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We present the pedestal structure, as determined from the high resolution Thomson scattering (HRTS) measurements, for a database of low and high triangularity (  0.22-0.39) 2.5MA, Type I ELMy H-mode JET plasmas after the installation of the new ITER-like Wall (JET-ILW). The database explores the effect of increasing deuterium fuelling and nitrogen seeding with a view to explain the observed changes in performance (edge and global). The low triangularity JET-ILW plasmas show no significant change in performance and pedestal structure with increasing gas dosing. These results are in good agreement with EPED1 predictions. At high triangularity, for pure deuterium fuelled JET-ILW plasmas, there is a 20-30% reduction in global performance and pressure pedestal height in comparison to JET-C plasmas. This reduction in performance is primarily due to a degradation of the temperature pedestal height. The global performance and pressure pedestal height of JET-ILW plasmas can be partially recovered to that of JET-C plasmas with additional nitrogen seeding [Giroud 2013]. This observed improvement in performance is predominately due to a significant increase in density pedestal height as well as a small increase in the temperature pedestal height. A key result with increasing deuterium fuelling for JET-ILW plasmas is there is no improvement in pressure pedestal height however the pedestal still widens which is inconsistent with the  = 0.076√ pol,ped scaling. Furthermore, a key result with increasing nitrogen seeding is the pressure pedestal widening is due to an increase in the temperature pedestal width whilst the density pedestal shows no clear trend. The comparison of EPED1 predictions with the measurements at high triangularity is complex as, for example, for pure deuterium fuelled plasmas there is very good agreement for the pedestal height but not the width. In addition, current EPED1 runs under-predict the pedestal height and width at high nitrogen seeding for JET-ILW plasmas however further work is required to determine the significance of these deviations. Understanding these deviations is essential as provides an insight to the physical mechanisms governing the pedestal structure and edge performance.

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“…21͒ and ASDEX-U ͑Ref. 22͒ groups, various small ELM regimes at JT-60U, 23,24 ASDEX-U, 25 NSTX, 26,27 JET, 28 C-Mod, 29 JFT-2M, 30,31 Compass-D ͑Ref. 32͒ and DIII-D, 33 and ELM-free operation in the QH-mode.…”

Section: Introductionmentioning

confidence: 99%

Effect of island overlap on edge localized mode suppression by resonant magnetic perturbations in DIII-D

Fenstermacher¹,

Evans²,

Osborne³

et al. 2008

Physics of Plasmas

150

230

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Recent DIII-D [J. L. Luxon et al., Nucl. Fusion 43, 1813 (2003)] experiments show a correlation between the extent of overlap of magnetic islands induced in the edge plasma by perturbation coils and complete suppression of Type-I edge localized modes (ELMs) in plasmas with ITER-like electron pedestal collisionality νe*∼0.1, flux surface shape and low edge safety factor (q95≈3.6). With fixed amplitude n=3 resonant magnetic perturbation (RMP), ELM suppression is obtained only in a finite window in the edge safety factor (q95) consistent with maximizing the resonant component of the applied helical field. ELM suppression is obtained over an increasing range of q95 by either increasing the n=3 RMP strength, or by adding n=1 perturbations to “fill in” gaps between islands across the edge plasma. The suppression of Type-I ELMs correlates with a minimum width of the edge region having magnetic islands with Chirikov parameter >1.0, based on vacuum calculations of RMP mode components excluding the plasma response or rotational shielding. The fraction of vacuum magnetic field lines that are lost from the plasma, with connection length to the divertor targets comparable to an electron-ion collisional mean free path, increases throughout the island overlap region in the ELM suppressed case compared with the ELMing case.

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Characterization of small ELM experiments in highly shaped single null and quasi-double-null plasmas in JET

Cited by 84 publications

References 29 publications

Pedestal conditions for small ELM regimes in tokamaks

Pedestal conditions for small ELM regimes in tokamaks

The H-mode pedestal structure and its role on confinement in JET with a carbon and metal wall

Effect of island overlap on edge localized mode suppression by resonant magnetic perturbations in DIII-D

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