Experiments on Li pellet injection into Heliotron E

Sergeev, V. Yu.; Khlopenkov, K.; Kuteev, B. V.; Sudo, S.; Kondo, K.; Zushi, H.; Besshou, S.; Sano, F.; Okada, H.; Mizuuchi, T.; Nagasaki, K.; Obiki, T.; Kurimoto, Yuji

doi:10.1088/0741-3335/40/10/009

Cited by 8 publications

(4 citation statements)

References 14 publications

(18 reference statements)

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“…This simulation additionally supports the existence of an enhanced ablation process in region II. It is necessary to point out that the feature of periphery zones with an 'enhanced' ablation have been observed previously in experiments with Li pellet injections into ECR-heated Heliotron E plasmas [22].…”

Section: Modelling Of Experiments and Discussionmentioning

confidence: 68%

Study of carbon pellet ablation in ECR-heated W7-AS plasmas

Ledl¹,

Burhenn

Lengyel

et al. 2004

Nucl. Fusion

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The ablation of carbon pellets injected into ECR-heated plasmas of Wendelstein 7-AS (W7-AS) has been investigated using a photographic technique with the aim of studying features of the ablation process in stellarator plasmas. The ablation rate profiles were measured assuming a proportionality of the C II radiation and the ablation rate. This assumption was confirmed experimentally and by simulations performed by a quasi-three-dimensional code. The fraction of continuum radiation, which is detected together with the C II line radiation (when using the light filters with finite spectral width), did not affect these measurements.No significant drifts of pellet clouds in the toroidal, poloidal and radial directions were observed in the C II line (723 nm) emission. From fast electron temperature measurements ( t = 10 µs) using ECE diagnostics, no indications of a pre-cooling wave were found.A difference between the ablation rates for discharges with low and high plasma density, which lies beyond the error bars, was observed. A specific zone of enhanced ablation was detected at the plasma periphery at high density. The appearance of such ablation enhancement, points to the existence of an additional local heat flux. However, the mechanism that could explain the enhanced ablation phenomena at high plasma densities remains unclear.

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Section: Modelling Of Experiments and Discussionmentioning

confidence: 68%

Study of carbon pellet ablation in ECR-heated W7-AS plasmas

Ledl¹,

Burhenn

Lengyel

et al. 2004

Nucl. Fusion

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“…Concerning metal-wall devices, an attempt was performed in Heliotron-E to reduce the plasma contamination by metallic impurities by Li-pellet injection, but no significant conditioning effect was observed although it was measured that the Li-coating survives ∼1-2 discharges after the end of the injection [235][236][237]. The same absence of effect was observed in ALCATOR-C Mod (first wall in molybdenum) and, globally, it seems that the good results obtained with Li-conditioning are only observed in carbon-wall machines [229].…”

Section: Wall Conditioningmentioning

confidence: 99%

Review: Pellet injection experiments and modelling

Pégouriè

2007

Plasma Phys. Control. Fusion

126

158

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During the last decade, significant progress has been made in the field of pellet injection with (1) the identification of the drift of the deposited material in the inhomogeneous magnetic field that opened the possibility of fuelling efficiently the plasmas from the high-field side of the torus, (2) the technique to mitigate ELMS in H-mode discharges with shallow pellet injection at high frequency and (3) with the development of high density, high performance scenarios close to the ITER requirements. Both the experimental and theoretical aspects of this domain are reviewed in this paper.

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“…The ablation model described in reference [8] has been used to analyze several discharges [8,14,16]. In order to test the implementation in M3D − C 1 , we have chosen one of those cases: an ASDEX-U-like plasma, which was reconstructed from the shot #3948 using the available information [8].…”

Section: Validating the Ablation Rate Implementation In M3d − Cmentioning

confidence: 99%

Modeling of carbon pellets disruption mitigation in an NSTX-U plasma

Clauser¹,

Jardin²,

Raman³

et al. 2021

Nucl. Fusion

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Single carbon pellet disruption mitigation simulations using M3D-C 1 were conducted for an NSTX-U-like plasma to support the electromagnetic pellet injection concept. A carbon ablation model has been implemented in M3D-C 1 and tested with available data. 2D simulations were conducted in order to estimate the amount of carbon needed to quench the plasma, finding that the content in a 1 mm radius vitreous carbon pellet (∼3.2 × 1020 atoms) would be enough if it is entirely ablated. 3D simulations were performed, scanning over pellet velocity and parallel thermal conductivity, as well as different injection directions and pellet concepts (solid pellets and shell pellets). The sensitivity of the thermal quench and other related quantities to these parameters has been evaluated. A 1 mm radius solid pellet only partially ablates at velocities of 300 m s−1 or higher, thus being unable to fully quench the plasma. To further enhance the ablation, approximations to an array of pellets and the shell pellet concept were also explored. 3D field line stochastization plays an important role in both quenching the center of the plasma and in heat flux losses, thus lowering the amount of carbon needed to mitigate the plasma when compared to the 2D case. This study constitutes an important step forward in ‘predict-first’ simulations for disruption mitigation in NSTX-U and other devices, such as ITER.

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Experiments on Li pellet injection into Heliotron E

Cited by 8 publications

References 14 publications

Study of carbon pellet ablation in ECR-heated W7-AS plasmas

Study of carbon pellet ablation in ECR-heated W7-AS plasmas

Review: Pellet injection experiments and modelling

Modeling of carbon pellets disruption mitigation in an NSTX-U plasma

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