PELLET: a computer routine for modeling pellet fueling in tokamak plasmas

Houlberg, W. A.; Iskra,; Howe, H.C.; Attenberger, S.E.

doi:10.2172/6235677

Cited by 13 publications

(22 citation statements)

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“…If the characteristic times for density increase and electron cooling by pellet ablation are shorter than that for the pellet motion, changes in the plasma parameters by pellet injection affect the pellet ablation itself. This mechanism is called self-limiting ablation [11]…”

Section: Fig 2 Dependence Of Ablation Rate \Dr P /Dt\ Of H 2 Pellet O...mentioning

confidence: 99%

An analysis of the ablation rate for solid pellets injected into neutral beam heated toroidal plasmas

1986

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A new model for calculating the ablation rate of a solid pellet injected into a neutral-beam-heated toroidal plasma is discussed. It is an extension of the neutral cloud shielding model introduced by Parks and Turnbull. Fluid equations describing a transonic stationary flow of neutral particles ablated from the pellet surface in the presence of both electron heat flux and of flux due to fast ions are derived and solved as an eigenvalue problem. -The effect of fast ions on the ablation rate is significant in low electron temperature and low density plasmas such as edge plasmas when the fast ion density is rather high. When the ablation due to fast ions is dominant and electron heat flux is negligible, the ablation rate is given by a scaling relation similar to that obtained in the case of electron heat flux only. -An example of an ablation rate profile is shown for a PDX tokamak-like plasma in a self-limiting approximation for electron temperature and density. The results are compared to those of the Milora model which includes fast ions.

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Section: Fig 2 Dependence Of Ablation Rate \Dr P /Dt\ Of H 2 Pellet O...mentioning

confidence: 99%

An analysis of the ablation rate for solid pellets injected into neutral beam heated toroidal plasmas

1986

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“…On the basis of the transonic-neutral-shielding model of Parks and Turnbull [ 12], in Section 4 the governing equation describing the ablation rate of the pellet along its trajectory is first derived for a smaller pellet where perturbation of the background plasma is negligible. To study the pellet/plasma interaction caused by a larger pellet, we adopted the self-limiting ablation model of Houlberg et al [15], thereby assuming that the injected pellet cools the background plasma adiabatically ahead of the advancing pellet.…”

Section: Introductionmentioning

confidence: 99%

On the correlation between the H_α-line emission rate and the ablation rate of a hydrogen pellet in tokamak discharges

Chang¹,

Thomsen²

1984

Nucl. Fusion

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By incorporating a simplified collisional-radiative model into a self-limited ablation model, the correlation between the emission rate of the H a -line and the ablation rate of a hydrogen pellet in tokamak discharges is studied. In normal Ohmically heated discharges, the fuel deposition profile is reproduced accurately by the H a -line emission profile, except for a slight delay of the maximum ablation rate with respect to the maximum emission rate.

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“…Since sawtoothing is not fully understood, a comment on the features of the sawtoothing model which are important to the simulation will be given after the presentation of the simulation results. Finally, pellet ablation is described by a familiar model [36] and the ablation model parameters are fixed by comparison with the observed ablation.…”

Section: Discussionmentioning

confidence: 99%

Feasibility of developing a cw OH chemical laser

Baĭkov¹,

Bashkin²,

Neshchimenko³

et al. 1984

Sov. J. Quantum Electron.

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In the Texas Experimental Tokamak, a discharge regime characterized by persistent peaked profiles was observed to be induced by pellet fuelling, and its transport properties were studied. The hallmark of the regime is the suppression of sawteeth, and the regime was attained by injecting hydrogen pellets to promptly double the plasma density. In each of several pairs of experiments, a pellet fuelled discharge was compared with an edge fuelled discharge with similar averaged electron density, plasma current and toroidal magnetic field in order to characterize the transport change and to look for causal changes in the plasma turbulence. The impurity, radiation and working gas particle profiles were more peaked for the pellet fuelled case. The values of rj t derived from measured ion temperature and density profiles for high density edge fuelled and pellet fuelled discharges indicate that ion pressure gradient driven turbulence should be reduced in the pellet fuelled case. The macroscopic effects were accompanied by microscopic changes. NUCLEAR FUSION. Vol.30. No.5 (1990) 903 ROWAN et al. pellet fuelled discharges. The effects of the reduction of an ion mode turbulence were sought in the energy confinement of the discharges, but it was found that for these experiments (tailored for the turbulence diagnostics) the energy flowing in the ion channel was not large enough to affect the energy confinement. Simulations were used to interpret some of the results. Discharge simulations which include the pellet injection can reproduce the sawtooth suppression. This result and known properties of discharges in which sawteeth are suppressed suggest that some of the profile effects (including peaking of the working gas particles) induced by pellet injection are due to sawtooth suppression. The particle peaking may cause the observed reduction in the turbulence which follows pellet injection. Measurements of turbulent density fluctuations in high density edge fuelled discharges give strong evidence that a component of the turbulence propagates in the ion diamagnetic direction and that this particular mode is reduced in

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PELLET: a computer routine for modeling pellet fueling in tokamak plasmas

Cited by 13 publications

References 0 publications

An analysis of the ablation rate for solid pellets injected into neutral beam heated toroidal plasmas

An analysis of the ablation rate for solid pellets injected into neutral beam heated toroidal plasmas

On the correlation between the H_α-line emission rate and the ablation rate of a hydrogen pellet in tokamak discharges

Feasibility of developing a cw OH chemical laser

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PELLET: a computer routine for modeling pellet fueling in tokamak plasmas

Cited by 13 publications

References 0 publications

An analysis of the ablation rate for solid pellets injected into neutral beam heated toroidal plasmas

An analysis of the ablation rate for solid pellets injected into neutral beam heated toroidal plasmas

On the correlation between the Hα-line emission rate and the ablation rate of a hydrogen pellet in tokamak discharges

Feasibility of developing a cw OH chemical laser

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On the correlation between the H_α-line emission rate and the ablation rate of a hydrogen pellet in tokamak discharges