Hybrid H-mode scenario with nitrogen seeding and type III ELMs in JET

Corre, Y.; Joffrin, E.; Monier‐Garbet, P.; Andrew, Y.; Arnoux, G.; Beurskens, M.; Brezinsek, S.; Brix, M.; Buttery, R. J.; Coffey, I.; Crombé, Kristel; Luna, E. de la; Felton, R.; Giroud, C.; Hacquin, S.; Hobirk, J.; Huber, A.; Imbeaux, F.; Jachmich, S.; Kempenaars, M.; Litaudon, X.; Leggate, H.; Loarer, T.; Maddison, G.; Rachlew, Elisabeth; Rapp, J.; Sauter, O.; Savchkov, A. V.; Telesca, G.; Widdowson, A.; Zastrow, K.‐D.; Zimmermann, O.

doi:10.1088/0741-3335/50/11/115012

Cited by 12 publications

(16 citation statements)

References 37 publications

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“…This work benefits from enhanced diagnostic capabilities compared with past seeding and fuelling studies at JET [14][15][16][17]. First, the fast high resolution infra-red (IR) camera system [12] allows for full inter-ELM power load profiles of the JET outer divertor.…”

Section: Diagnosticsmentioning

confidence: 99%

Integration of a radiative divertor for heat load control into JET high triangularity ELMy H-mode plasmas

et al. 2012

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Experiments on JET with a carbon-fibre composite wall have explored the reduction of steady-state power load in an ELMy H-mode scenario at high Greenwald fraction ∼0.8, constant power and close to the L to H transition. This paper reports a systematic study of power load reduction due to the effect of fuelling in combination with seeding over a wide range of pedestal density ((4–8) × 1019 m−3) with detailed documentation of divertor, pedestal and main plasma conditions, as well as a comparative study of two extrinsic impurity nitrogen and neon. It also reports the impact of steady-state power load reduction on the overall plasma behaviour, as well as possible control parameters to increase fuel purity. Conditions from attached to fully detached divertor were obtained during this study. These experiments provide reference plasmas for comparison with a future JET Be first wall and an all W divertor where the power load reduction is mandatory for operation.

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Section: Diagnosticsmentioning

confidence: 99%

Integration of a radiative divertor for heat load control into JET high triangularity ELMy H-mode plasmas

et al. 2012

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“…The improvement is caused by increased temperatures in the core and at the pedestal, while no changes in the density profile shape occur. A related behaviour may be the partial recovery of the confinement reduction associated with the type-III pedestal observed in a nitrogen seeded JET hybrid scenario, where core temperatures slightly increased with increasing radiative fraction [35]. Quantitative theoretical predictions of the effect of impurity seeding on core plasma profiles are difficult, in particular in the transitional region between dominant ITG and trapped electron mode (TEM) instabilities, which have opposite trends of the collisionality dependence of the density gradient [36] [37].…”

Section: Energy Confinement Issuesmentioning

confidence: 99%

Plasma surface interactions in impurity seeded plasmas

Kallenbach

Balden

Dux

et al. 2011

Journal of Nuclear Materials

122

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With tokamak devices developing towards higher heating powers, and carbon plasma facing components being increasingly replaced by high-Z materials like tungsten, impurity seeding for radiative power dissipation gains more importance. This review summarizes the core and divertor radiative characteristics of potential seeding species, namely noble gases and nitrogen. Due to its radiative capability below 10 eV, nitrogen turns out to be a suitable replacement for carbon as a divertor radiator. For typical plasma parameters and high radiation levels, it becomes the most important eroding species for high-Z plasma fac-

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“…The electron temperature scale length r Te may be either ∼ ρ θ or > ρ θ . The ordering r T i > r n is satisfied in the pedestal on many present tokamaks, including DIII-D, JET, ASDEX-U, NSTX, and MAST [41][42][43][44][45][46][47][48][49][50][51] , when inter-ELM or non-ELMy (without RMP) profiles are carefully examined, though exceptions exist such as I-mode and EDA H-Mode in Alcator C-Mod 52 . Both entropy considerations 53 and data 45,47 suggest r T i resists becoming as small as ρ θ when collisionality is low, while r n and r Te are not similarly constrained.…”

Section: Introductionmentioning

confidence: 99%

“…. Interestingly, the new n g terms in(44) and(43) and the new L nT term in(45) are quadratic in the gradients.…”

mentioning

confidence: 99%

Local and global Fokker–Planck neoclassical calculations showing flow and bootstrap current modification in a pedestal

Landreman

Ernst

2012

Plasma Phys. Control. Fusion

104

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In transport barriers, particularly H-mode edge pedestals, radial scale lengths can become comparable to the ion orbit width, causing neoclassical physics to become radially nonlocal. In this work, the resulting changes to neoclassical flow and current are examined both analytically and numerically. Steep density gradients are considered, with scale lengths comparable to the poloidal ion gyroradius, together with strong radial electric fields sufficient to electrostatically confine the ions. Attention is restricted to relatively weak ion temperature gradients (but permitting arbitrary electron temperature gradients), since in this limit a δf (small departures from a Maxwellian distribution) rather than full-f approach is justified. This assumption is in fact consistent with measured inter-ELM H-Mode edge pedestal density and ion temperature profiles in many present experiments, and is expected to be increasingly valid in future lower collisionality experiments. In the numerical analysis, the distribution function and Rosenbluth potentials are solved for simultaneously, allowing use of the exact field term in the linearized Fokker-Planck-Landau collision operator.In the pedestal, the parallel and poloidal flows are found to deviate strongly from the best available conventional neoclassical prediction, with large poloidal variation of a different form than in the local theory. These predicted effects may be observable experimentally. In the local limit, the Sauter bootstrap current formulae appear accurate at low collisionality, but they can overestimate the bootstrap current near the plateau regime. In the pedestal ordering, ion contributions to the bootstrap and Pfirsch-Schlüter currents are also modified. a) landrema@mit.edu

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Hybrid H-mode scenario with nitrogen seeding and type III ELMs in JET

Cited by 12 publications

References 37 publications

Integration of a radiative divertor for heat load control into JET high triangularity ELMy H-mode plasmas

Integration of a radiative divertor for heat load control into JET high triangularity ELMy H-mode plasmas

Plasma surface interactions in impurity seeded plasmas

Local and global Fokker–Planck neoclassical calculations showing flow and bootstrap current modification in a pedestal

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