Local effects of ECRH on argon transport in L-mode discharges at ASDEX Upgrade

Sertoli, M.; Angioni, C.; Dux, R.; Neu, R.; Pütterich, T.; Igochine, V.

doi:10.1088/0741-3335/53/3/035024

Cited by 60 publications

(108 citation statements)

References 26 publications

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“…In [53,54] it has been found that impurity accumulation occurs when turbulent transport in the plasma core is weak, and the neoclassical transport becomes important. The cleaning effect of large turbulent core transport is not only based on diffusive effects, but also supported by a turbulent outward pinch for the impurities requiring steep temperature gradients [55,56]. The radiation/heating balance in the core of the presented Pulse No: 81913 (Fig.5) reveals radiative cooling of similar size as the local heating power thereby decreasing the core T e and flattening the T e gradients leading to a feedback loop of decreasing transport and increasing radiation [49].…”

Section: W Accumulationmentioning

confidence: 77%

First operation with the JET International Thermonuclear Experimental Reactor-like wall

et al. 2013

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AbstrAct.To consolidate ITER design choices and prepare for its operation, JET has implemented ITER's plasma facing materials, namely Be at the main wall and W in the divertor. In addition, protection systems, diagnostics and the vertical stability control were upgraded and the heating capability of the neutral beams was increased to over 30 MW. First results confirm the expected benefits and the limitations of all metal plasma facing components (PFCs), but also yield understanding of operational issues directly relating to ITER. H-retention is lower by at least a factor of 10 in all operational scenarios compared to that with C PFCs. The lower C content (Section 1factor 10) have led to much lower radiation during the plasma burn-through phase eliminating breakdown failures.Similarly, the intrinsic radiation observed during disruptions is very low, leading to high power loads and to a slow current quench. Massive gas injection using a D 2 /Ar mixture restores levels of radiation and vessel forces similar to those of mitigated disruptions with the C wall. Dedicated L-H transition experiments indicate a reduced power threshold by 30%, a distinct minimum density and pronounced shape dependence. The L-mode density limit was found up to 30% higher than for C allowing stable detached divertor operation over a larger density range. Stable H-modes as well as the hybrid scenario could be only re-established when using gas puff levels of a few 10 21 es −1. On average the confinement is lower with the new PFCs, but nevertheless, H factors up to 1 (H-Mode) and 1.3 (at b N ≈ 3, hybrids) have been achieved withWconcentrationswell below themaximum acceptable level.

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Section: W Accumulationmentioning

confidence: 77%

First operation with the JET International Thermonuclear Experimental Reactor-like wall

et al. 2013

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“…In the edge of the core plasma but still on the inside of the ETB, impurity transport is dominated by plasma turbulence and diffusion coefficients have typical values of a few m 2 s −1 , while v/D values are low. This was shown by investigations on helium, neon [22], silicon [23] and argon [24]. Further out in the ETB, recent impurity transport investigations on helium, carbon, neon and argon have shown, that the radial transport in the ETB between ELMs is in accordance with collisional transport coefficients [9,8] D neo = D CL + D P S and the collisional radial drift velocity v neo is v neo = v CL + v P S .…”

Section: Impurity Transport Modelmentioning

confidence: 87%

Main chamber sources and edge transport of tungsten in H-mode plasmas at ASDEX Upgrade

2011

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Abstract. In the fully tungsten clad ASDEX Upgrade, the sputtering rates of tungsten have been determined at all relevant plasma facing components using fast spectroscopic measurements with temporal resolution down to 0.5 ms. The sputtering strongly increases during an edge-localised mode (ELM) and the ELMs are often the dominant cause for tungsten sputtering. A modelling approach was employed to calculate the tungsten source at the limiters and the resulting tungsten density at the pedestal top inside of the H-mode edge transport barrier (ETB). In the ETB, it is assumed that tungsten transport is collisional, i.e. behaves like other impurities. The collisional transport leads to strong inward drifts and steep density gradients in the ETB, which are flattened during an ELM causing an efflux of tungsten. The collisional transport in the ETB is also calculated for typical ITER conditions and the resulting tungsten density profiles as well as the transport of the helium ash through the ETB are evaluated.

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“…Detailed transport investigations using tracer impurities show that the local heating leads to a strong increase of anomalous transport [53]. This could be further detailed in [54] where the Ar tracer transport was compared to quasi-linear gyro-kinetic simulations, which qualitatively reproduce the positive convection and its decreasing trend for radii outside the ECRH deposition radius. However, for the most central ECR-heated discharge analysed, the resulting strong positive (outward) convection is probably not of turbulent nature but could be caused by the strong MHD activity present within the q = 1 surface.…”

Section: W Transport and Contentmentioning

confidence: 94%

Overview on plasma operation with a full tungsten wall in ASDEX Upgrade

Neu¹,

Kallenbach²,

Balden³

et al. 2013

Journal of Nuclear Materials

109

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Operation with all tungsten plasma facing components has become routine in ASDEX Upgrade. The conditioning of the device is strongly simplified and short glow discharges are used only on a daily basis. The long term fuel retention was reduced by more than a factor of 5 as demonstrated in gas balance as well as in post mortem analyses. Injecting nitrogen Preprint submitted to Elsevier 23 November 2012for radiative cooling, discharges with additional heating power up to 23 MW have been achieved, providing good confinement (H98 y2 = 1), divertor power loads around 5 MW m −2 and divertor temperatures below 10 eV. ELM mitigation by pellet ELM pacemaking or magnetic perturbation coils reduces the deposited energy during ELMs, but also keeps the W density at the pedestal low. As a recipe to keep the central W concentration sufficiently low, central (wave) heating is well established and low density H-Modes could be re-established with the newly available ECRH power of up to 4 MW. The ICRH induced W sources could be strongly reduced by applying boron coatings to the poloidal guard limiters.

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Local effects of ECRH on argon transport in L-mode discharges at ASDEX Upgrade

Cited by 60 publications

References 26 publications

First operation with the JET International Thermonuclear Experimental Reactor-like wall

First operation with the JET International Thermonuclear Experimental Reactor-like wall

Main chamber sources and edge transport of tungsten in H-mode plasmas at ASDEX Upgrade

Overview on plasma operation with a full tungsten wall in ASDEX Upgrade

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