Local-density increment from an ablated deuterium pellet in the TFTR tokamak

Mansfield, D.K.; Janos, A.; Owens, D. K.; Schmidt, G. L.; Bell, M.G.; Cavallo, A.; Fredrickson, E. D.; Ramsey, A. T.; Taylor, G.

doi:10.1103/physrevlett.66.3140

Cited by 13 publications

(13 citation statements)

References 10 publications

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“…14 m for the total plasmoid). This value is close to 2πR in the case of Tore Supra, in agreement with the fact that fast interferometry measurements exhibit in general only one peak during a pellet injection [18] (also see [24] for similar measurements in TFTR). Finally, the drift velocity V D and corresponding acceleration g are shown in figure 8(f ).…”

Section: As ėEsupporting

confidence: 86%

Homogenization of the pellet ablated material in tokamaks taking into account the ∇B-induced drift

et al. 2006

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A model of the pellet deposition profile is presented, which describes in a self-consistent way the homogenization process and the simultaneous drift of the ablated material. Its main features are (i) that the drift is stopped by a parallel current that appears in the drifting flux tube and reduces the polarization of the expanding ablatant and (ii) that the pellet material does not move as a solid body but homogenizes in a radial interval of extent equal to its displacement. From the pellet and plasma pre-injection characteristics, the model yields the post-injection density and temperature profiles, allowing a quantitative comparison with measurements. The simulation results are compared with experimental data for both the homogenization phase and ∇B-induced displacement. In particular, (i) the calculated characteristics of the homogenization and drift (time constants and velocities) are in agreement with the measurements, (ii) for pellets launched from the low field side (LFS), the model reproduces the dependence of both the fuelling efficiency and the outward displacement on the pellet penetration and (iii) for pellets launched from the high field side (HFS), which are less documented, the calculated fuelling efficiency is always equal to 100%, larger than what is observed, suggesting a transient increase in the plasma (radial) transport. Practically, the main results are that the displacement is smaller for the HFS than for the LFS launched pellets and that, for deep fuelling, one must inject the pellet along the drift direction.

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Section: As ėEsupporting

confidence: 86%

Homogenization of the pellet ablated material in tokamaks taking into account the ∇B-induced drift

et al. 2006

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“…A shock is formed in front of the cloud, inside which the density is homogeneous. For such conditions, the time-history of the density at a given location reproduces qualitatively the peak structure observed in TFTR [82]. For higher ablation rates, the cloud heating is slower and the density profile remains more strongly peaked during the major part of the homogenization phase, figure 17.…”

Section: Parallel Expansion and Potential Perturbationsupporting

confidence: 53%

“…The parallel expansion velocity of the deposited material was measured in TFTR from the analysis of the dynamics of the density increase at the plasma edge after the injection of a pellet, or of fragments of pellets [82]. Two diagnostics were used: an x-ray camera and a FIR interferometer with a time resolution of ∼10 µs, showing two density peaks propagating symmetrically along the field lines.…”

Section: Parallel Expansionmentioning

confidence: 99%

Review: Pellet injection experiments and modelling

Pégouriè

2007

Plasma Phys. Control. Fusion

125

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 computed outcomes are presented below: V measured = (2.93 ± 2.34) × 10 4 m s −1 (red diamonds in figure 12(c)). Remarkably, this measured value is in alignment with the findings reported from the TFTR experiment [13]. Importantly, it should be underscored that the experimentally determined velocity closely approximates V HPI2 and is notably lower than C s0 .…”

Section: Discussionsupporting

confidence: 89%

“…However, a noticeable gap persists in the experimental exploration during the homogenization process of ablated particles. In the context of such research, an interferometer coupled with an x-ray camera for line-integrated density measurements were employed in TFTR, revealing the velocity of parallel expansion along the magnetic field of pellet ablatant [8,13]. It was found that the entire homogenization period lasted less than 1 ms, with the parallel expansion velocity gradually decreasing from approximately 1 × 10 5 m s −1 at its initiation to around 3 × 10 4 m s −1 after roughly 200 µs.…”

Section: Introductionmentioning

confidence: 99%

Observation of local density increase during pellet homogenization on EAST

Huang,

Zhang,

Zhang

et al. 2023

Nucl. Fusion

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By combining the X-mode polarized lower and upper cut-off reflections obtained from the density profile reflectometer, we have successfully attained a comprehensive density profile spanning from the edge to the core region in pellet injection (PI) experiments on EAST. During the homogenization process after PI on EAST, an innovative method was introduced to quantify the local density increase. This approach employed the distinctive ‘dual-reflection’ phenomenon observed in the EAST microwave reflectometer, encompassing measurements of both the X-mode lower and upper cut-off frequencies. Furthermore, experimental investigations were carried out on EAST to comprehensively explore the parallel and poloidal expansion of the high-density pellet cloud. Notably, this study marks the first instance of measuring expansion velocities of pellet materials in both parallel and poloidal directions on EAST. A comparative analysis was performed initially between these experimental measurements and simulation results obtained from the HPI2 code, marking a pivotal stride towards enhancing its applicability in EAST.

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Local-density increment from an ablated deuterium pellet in the TFTR tokamak

Cited by 13 publications

References 10 publications

Homogenization of the pellet ablated material in tokamaks taking into account the ∇B-induced drift

Homogenization of the pellet ablated material in tokamaks taking into account the ∇B-induced drift

Review: Pellet injection experiments and modelling

Observation of local density increase during pellet homogenization on EAST

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