Pellet ablation studies on TORE SUPRA

Pégouriè, B.; Picchiottino, J M; Drawin, H. W.; Géraud, A.; Chatelier, M.

doi:10.1088/0029-5515/33/4/i06

Cited by 35 publications

(32 citation statements)

References 18 publications

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“…Such an approach yields, in combination with the self-consistent calculation of the cloud expansion characteristics along the magnetic field lines, pellet penetration depths and/or radiation characteristics [8,9] that are in agreement with experimental observations. Nevertheless, using the flux tube size for discretization imposes a periodicity on the system that may not always reflect physical reality.…”

Section: Introductionsupporting

confidence: 70%

Two (‘plus one’)-dimensional simulation of pellet cloud evolution in the poloidal plane with a prescribed neutral particle source strength

Lalousis

Lengyel²,

Schneider

2008

Plasma Phys. Control. Fusion

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Abstract. The evolution of pellet clouds in magnetically confined thermonuclear plasmas is studied by means of a time-dependent two-dimensional resistive MHD model applicable to the poloidal plane of a plasma torus. A massive neutral particle source representing a pellet traverses the plasma and continuously releases cold and unionized particles. Its motion is confined to a poloidal plane, which is thus considered to be a symmetry plane of the model. The conservation equations supplemented by Maxwell's equations, Ohm's generalized law, and a number of rate equations are solved for the symmetry plane. To each mesh point of the Eulerian grid in the poloidal plane, a toroidal 'flux tube' is attached. The field-aligned expansion of the ablated substance in these flux tubes and the corresponding change of the state parameters are computed in a Lagrangian approximation. Hence the two-dimensional Eulerian resistive MHD code is operated alternating with the one-dimensional Lagrangian routine. In the first series of computations, the neutral particle source strength is a prescribed input parameter, the applied magnetic field as well as the initial state parameters of the background plasma are uniform. Results of these calculations are presented and the solutions obtained are discussed.

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Section: Introductionsupporting

confidence: 70%

Two (‘plus one’)-dimensional simulation of pellet cloud evolution in the poloidal plane with a prescribed neutral particle source strength

Lalousis

Lengyel²,

Schneider

2008

Plasma Phys. Control. Fusion

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“…The corresponding calculations were provided in [31,43,44] and confirmed, in further analyses, by Pégourié [2,45]) by means of one-dimensional single-fluid numerical MHD modelling. The first numerical results applicable to reactore-grade plasmas were obtained with the help of a resisitve MHD code about 15 years ago [13].…”

Section: Wwwcpp-journalorgsupporting

confidence: 53%

“…The injection of cryogenic hydrogen isotope pellets became a standard method for particle supply to the interior of large-scale experimental fusion devices such as JET, ASDEX-Upgrade, Tore Supra, DIII-D, and others (see [1][2][3][4][5][6][7][8]). Impurity pellets may be injected into plasmas to enhance their radiative properties (discharge quenching), or for using the impurity particles as tracers in transport studies.…”

Section: Introductionmentioning

confidence: 99%

Pellet – Plasma Interaction: an Analysis of Pellet Injection Experiments by Means of a Multi‐Dimensional MHD Pellet Code

Lengyel

Schneider

Kardaun

et al. 2008

Contrib. Plasma Phys.

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This work is aimed at the analysis of pellet injection experiments by means of a magnetohydrodynamic code that computes the processes of pellet ablation, expansion, ionization, and magnetic confinement of the ablated substance. In particular, experimental pellet injection scenarios stemming from the tokamak ASDEX-Upgrade (D2 pellets) and the stellarator W7-AS (carbon pellets) are analyzed by means of this time-dependent quasithree-dimensional MHD pellet code. Pellet penetration depths measured in ASDEX-Upgrade at LFS (lowfield-side) and HFS (high-field-side) pellet injection, are compared with computational results.It was found that the penetration depths of deuterium pellets observed in about twenty randomly selected LFS and HFS injection scenarios could accurately be reproduced by a single code in which drift effects were intentionally ignored. This may be understood as an indication of the negligible effect drift exerts on the ablation process. At the same time, the distribution of the ablated and partially ionized substance may very well be affected by the drift of the ionized particles in the direction of the decreasing magnetic field.With the help of the Dα radiation patterns observed, the magnitudes of the heat fluxes affecting the pellet and the ablation cloud were estimated. The calculations show that the thermal heat fluxes (electron and ion) acting along the magnetic field lines are not sufficient to explain the size of the radiating filaments observed.The effect of extra-thermal electrons on the ablation history of pellets injected in W7-AS is demonstrated: the particle end energy fluxes causing measured pellet ablation profiles are determined.Based on a statistically well-designed computational data set, an empirical scaling of the penetration depths in terms of the background plasma parameters was attempted. It is shown that the form of the temperature profile of the background plasma cannot be ignored while deriving scaling laws; the specification of the central or the bulk temperature alone is insufficient.Quantitative data are provided for the magnitudes of various additional processes such as the anomalous thermal conduction across the field lines or the grad(B)-induced drift of the shielding cloud surrounding the pellet.The modelling of supersonic gas jets, a fuelling method that appears to be an alternative to pellet injection, is also considered. Since the massive stream of a cold gas represents a disturbance for the recipient plasma similar to that of a pellet, its dynamics can be described by the same means as the evolution of pellet clouds.

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“…The self-regulation of the ablation was taken into account presuming that the heat flux of the target plasma reaching the pellet surface is always zero. The hydrodynamic equations were solved by using a steady state assumption, and the N ′ ablation rate (the total number of ablated particles/second) was obtained as a power function of the plasma electron temperature T e [ eV], electron density n e [ m −3 ] and the pellet radius r p [ mm] [10] :…”

Section: Introductionmentioning

confidence: 99%

Role of shielding in modelling cryogenic deuterium pellet ablation

et al. 2008

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Abstract. For the better characterization of pellet ablation, the numerical LLP code has been enhanced by combining two relevant shielding mechanism: that of the spherically expanding neutral cloud surrounding the pellet and of the field elongated ionized material forming a channel flow. In contrast to our expectations the presence of the channel flow can increase the ablation rate although it reduces the heat flux traveling through it. The contribution of the different shielding effects in the ablation process is analyzed for several pellet and plasma parameters and an ablation rate scaling is presented based on simple regression in the ASDEX Upgrade pellet and plasma parameter range. Finally the simulated results are compared to experimental data from typical ASDEX Upgrade discharges.

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Pellet ablation studies on TORE SUPRA

Cited by 35 publications

References 18 publications

Two (‘plus one’)-dimensional simulation of pellet cloud evolution in the poloidal plane with a prescribed neutral particle source strength

Two (‘plus one’)-dimensional simulation of pellet cloud evolution in the poloidal plane with a prescribed neutral particle source strength

Pellet – Plasma Interaction: an Analysis of Pellet Injection Experiments by Means of a Multi‐Dimensional MHD Pellet Code

Role of shielding in modelling cryogenic deuterium pellet ablation

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