A Revised Neutral Gas Shielding Model for Pellet-Plasma Interactions

Milora, S.L.; Foster, C.A.

doi:10.1109/tps.1978.4317167

Cited by 86 publications

(90 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Pellet speeds in excess of 1000 m/s will not likely survive the curved guide tubes for HFS injection in a reactor device. The penetration depth of pellets from the NGS model and from the international pellet database for LFS injection is a weak function of the pellet speed (h a [2,3,4], so it remains to be seen how serious a limitation this presents. The benefits of higher fueling efficiency and lower ELM magnitude may compensate for a lower pellet speed.…”

Section: N Discussionmentioning

confidence: 99%

“…Much effort has been devoted in past pellet fueling experiments to understand pellet ablation and pellet induced changes in plasma transport. These studies have yielded an extensive validation of the neutral gas shielding (NGS) scaling law for pellet penetration [2,3,41 and have shown the capability of pellet fueling to strongly modify the density profile shape. The resulting density profile modification from pellet injection was shown in JET and TFTR experiments to disagree with conventional pellet ablation theory [5] and suggested that a fast outward radial transport may occur during the pellet ablation and toroidal symmetrization process.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Deposition of Fuel Pellets Injected into Tokamak Plasmas

1998

View full text Add to dashboard Cite

A b U-Oak Ridge, TN 37831-8071 (423) 574-1164 ABSTRACT Pellet injection has been used on tokamak devices in a number of experiments to provide plasma fueling and density profile control. The mass deposition of these fuel pellets, defined as the change in density profile caused by the pellet, has been found to show an outward displacement of the ablated material from that expected by mapping the theoretical ablation rate onto the flux surfaces. This suggests that fast transport of the pellet ablatant occurs during the flow along field lines that may be driven by VB drift effects. A comparison of the deposition of pellets from different machines shows similar behavior. Initial results from alternative injection locations designed to take advantage of the outward ablatant drift is presented.

show abstract

Section: N Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deposition of Fuel Pellets Injected into Tokamak Plasmas

1998

View full text Add to dashboard Cite

show abstract

“…The neutral gas shielding (NGS) model [8,9] is a simple theoretical model describing pellet ablation in high temperature plasmas. A neutral shielding cloud around the pellet is formed by the incident energy flux from a background plasma and assumes a steady state and shockfree transonic flow which is continuously accelerated to supersonic flow.…”

Section: The Ngs Ablation Modelmentioning

confidence: 99%

“…Only the thermal effect of electrons on pellet ablation is considered in the original NGS ablation model [8,9]. However, the extra-thermal effect (involving fast ions and energetic electrons, etc.)…”

Section: Impact Of Energetic Ions On Pellet Ablationmentioning

confidence: 99%

“…This allows the discussion of drift motion as a secondary problem. With respect to the ablation process, the neutral gas shielding (NGS) model [8,9], which estimates heat flux due to thermal electrons and evaluates the shielding effect of ablated neutral gas against it, has been widely accepted as a standard model for explaining the results of tokamak experiments. A study of the international pellet ablation database (IPADBASE) has indicated that the penetration depths in the different devices follows regression scaling whose expression is similar to NGS scaling under the condition of scatter in the scaling data of ohmic, NBI, and ICRH plasmas [10].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Observation of the Effect of Energetic Ions on Pellet Ablation in the Large Helical Device

Hoshino

Sakamoto

Yamada

et al. 2006

Plasma and Fusion Research

View full text Add to dashboard Cite

Ablation of a solid hydrogen pellet in hot plasmas was investigated in the Large Helical Device (LHD). The penetration depth of the injected pellets in the experiment was compared to a theoretical model employing ablation due to the heat flux of fast ions as well as thermal electrons. Shallower penetration than that predicted based on the model considering only electrons was observed in LHD plasmas in the presence of highly energetic (up to 180 keV) fast ions due to neutral beam injection (NBI). This discrepancy can be quantified by the contribution of fast ions in terms of the stored energy of fast ions. The ablation model calculation taking into consideration the effect of thermal electrons and fast ions agrees with the experimental results obtained by LHD. Scaling which includes the fast-ion effect on penetration depth in LHD was compared with the wider multi-experiment database (IPADBASE) [L.R. Baylor et al., Nucl. Fusion 37, 445 (1997)].

show abstract

Simulation study on the vapour shielding at solid walls under transient heat loads using weighted particle model

Ibano

Kikuchi

Tanaka

et al. 2018

Contributions to Plasma Physics

View full text Add to dashboard Cite

Vapour shielding at solid walls is expected for a future fusion reactor in case of large heat load due to transient events. In order to estimate the dissipation of the incoming heat flux by the vapour shielding, a simulation code called PIXY, using a weighted particle model, is developed. First, a validation study is undertaken. Vapour shielding of an aluminium‐coated tungsten specimen was experimentally observed in a plasma gun device. Results are reproduced by the PIXY simulation. Then, the code is applied to the transient edge‐localized mode (ELM) heat flux for the reactor condition. It was found that the ion–neutral collision, as well as radiative cooling, is a dominant phenomenon for the heat flux dissipation in both cases. As the maximum heat flux increases, oscillating phenomena appear remarkably, which have been observed in other experimental studies on vapour shielding.

show abstract

A Revised Neutral Gas Shielding Model for Pellet-Plasma Interactions

Cited by 86 publications

References 4 publications

Deposition of Fuel Pellets Injected into Tokamak Plasmas

Deposition of Fuel Pellets Injected into Tokamak Plasmas

Observation of the Effect of Energetic Ions on Pellet Ablation in the Large Helical Device

Simulation study on the vapour shielding at solid walls under transient heat loads using weighted particle model

Contact Info

Product

Resources

About