Laser blow-off injected impurity particle confinement times in JET and Tore Supra

Mattioli, M.; Giannella, R.; Myrnäs, R; DeMichelis, C.; Denne-Hinnov, B.; Wit, T. Dudok de; Magyar, G.

doi:10.1088/0029-5515/35/9/i05

Cited by 45 publications

(61 citation statements)

References 27 publications

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“…It is interesting to note that the measured impurity diffusivity in C-Mod L-mode plasmas decreases with plasma current as D eff ∝ I P −.7 [1]. Similar observations have been made on other devices [49,50,51]. At these outer radii with the electron temperature below 1 keV, the dominant population mechanism for the upper levels of the Ar 17+ Ly α doublet is radiative recombination of fully stripped Ar 18+ , which must be born in the plasma core and then transported radially outwards.…”

Section: Discussionsupporting

confidence: 79%

Up/down impurity density asymmetries in C-Mod plasmas

Rice¹,

Reinke²,

Cao³

et al. 2018

Nucl. Fusion

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Brightness profiles of x-ray emission from H-like Ar 17+ exhibit a distinct up/down asymmetry under certain operating conditions in C-Mod plasmas, indicating that impurity densities are not constant on flux surfaces with r/a between ∼0.8 and ∼0.95. In Land I-mode plasmas, there is an x-ray brightness excess, up to a factor of 8, on the side opposite to the ion B×∇B drift direction. This effect is not observed in H-mode plasmas, presumably due to edge impurity transport being dominated by a strong inward pinch, which is absent in L-and I-mode. The magnitude of the asymmetry in L-and I-mode decreases with increasing plasma current, similar to the observed decrease in radial impurity diffusivity. In I-mode, where the codependence between electron density and temperature can be broken with ICRF heating power, the asymmetry magnitude is found to decrease with increasing density and with increasing edge temperature at fixed density. These measurements exhibit some qualitative features of neo-classical expectations but the observed asymmetry magnitude is much larger than predicted and some scalings with plasma parameters are not seen. The up/down asymmetry appears to be largest when the cross field impurity diffusivity is the highest.

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Section: Discussionsupporting

confidence: 79%

Up/down impurity density asymmetries in C-Mod plasmas

Rice¹,

Reinke²,

Cao³

et al. 2018

Nucl. Fusion

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“…The core impurity confinement time in Ohmic plasmas has been found to increase with increasing plasma current at fixed magnetic field [28,29,35,73]. Similar behavior is exhibited in ICRF heated L-mode discharges [43], as seen in Fig.8 Fig.9, capturing the same trend as seen in purely Ohmic plasmas.…”

Section: L-modesupporting

confidence: 53%

“…Similar behavior is exhibited in ICRF heated L-mode discharges [43], as seen in Fig.8 Fig.9, capturing the same trend as seen in purely Ohmic plasmas. The solid curve is proportional to I p .68 which was found from a regression analysis of C-Mod data [43]; the dashed curve is proportional to I p .31 which was derived from observations from JET and Tore Supra [35]. This dependence on plasma current has been reproduced in gyro-kinetic simulations of impurity confinement in the core temperature gradient region (0.3 < r/a < 0.6) [43] in C-Mod discharges.…”

Section: L-modementioning

confidence: 74%

Core impurity transport in Alcator C-Mod L-, I- and H-mode plasmas

Rice¹,

Reinke

Gao³

et al. 2015

Nucl. Fusion

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Core impurity transport has been investigated for a variety of confinement regimes in Alcator C-Mod plasmas from x-ray emission following injection of medium and high Z materials. In Ohmic L-mode discharges, impurity transport is anomalous (D eff ≫ D nc ) and changes very little across the LOC/SOC boundary. In ICRF heated Lmode plasmas, the core impurity confinement time decreases with increasing ICRF input power (and subsequent increasing electron temperature) and increases with plasma current. Nearly identical impurity confinement characteristics are observed in I-mode plasmas. In EDA H-mode discharges the core impurity confinement times are much longer. There is a strong connection between core impurity confinement time and the edge density gradient across all confinement regimes studied here. Deduced central impurity density profiles in stationary plasmas are generally flat, in spite of large amplitude sawtooth oscillations, and there is little evidence of impurity convection inside of r/a = 0.3 when averaged over sawteeth.

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“…, similar to that of the plasma energy confinement [19]. Remarkably, in the JET-Tore Supra studies, the total energy confinement time exceeded the impurity energy confinement time by a factor of 2.5 on average, whilst for TCV experiments, as reported here and previously [5], the impurity confinement time is the larger with The 1-D simulation code STRAHL [22,23] has been used to estimate the transport parameters D edge and v edge of the impurities for two injections in plasmas whose currents were respectively below and above the threshold.…”

Section: Ecrh Power Dependencementioning

confidence: 61%

Effects of ECRH power and safety factor on laser blow-off injected impurity confinement in TCV

Scavino

Bakos

Weisen

et al. 2004

Plasma Phys. Control. Fusion

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Evidence from the injection into the TCV device of laser ablated, non-recycling silicon impurities, shows that the transport of impurities confinement can be remarkably different from that of energy. The ratio of impurity to energy confinement times ranges from near unity in Ohmic discharges to 5 in the presence of high power ECCD. In Ohmic discharges in Deuterium, above a threshold of density and of safety factor near q 95 =4.5, the impurity confinement time increases abruptly by a factor of 2 and is sometimes accompanied by indefinite retention of non-recycling impurities within the sawtooth mixing radius, despite the continued presence of sawteeth.

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Laser blow-off injected impurity particle confinement times in JET and Tore Supra

Cited by 45 publications

References 27 publications

Up/down impurity density asymmetries in C-Mod plasmas

Up/down impurity density asymmetries in C-Mod plasmas

Core impurity transport in Alcator C-Mod L-, I- and H-mode plasmas

Effects of ECRH power and safety factor on laser blow-off injected impurity confinement in TCV

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