Radial displacement of pellet ablation material in tokamaks due to the grad-B effect

Parks, P.B.; Sessions, W. D.; Baylor, L. R.

doi:10.1063/1.874052

Cited by 107 publications

(172 citation statements)

References 15 publications

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“…The absolute pellet penetration depth for inboard launch is about twice that of the outboard launch. The deeper penetration of the high-field-side injection [482,486] is attributed to the ∇B and outward curvature-drift force on the plasmoid formed around the pellet [487,483,488]. The observed increase in penetration depth with inboard launch has been confirmed in several machines [489,490,491,492].…”

Section: Pellet Fuellingmentioning

confidence: 52%

Chapter 4: Power and particle control

Divertor¹,

Database²,

Editors³

1999

Nucl. Fusion

282

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Abstract.Progress, since the ITER Physics Basis publication, in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are : energy transport in the SOL in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main chamber material elements, ELM energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low and high Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma-materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas : refinement of the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a 2 major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral-neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma-materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed. Introduction.This chapter outlines the significant progress achieved since the ITER Physics Basis in understanding basic scrape-off layer (SOL) and divertor processes in a tokamak. The interaction of plasma with first-wall surfaces will have considerable impact on the performance of fusion plasmas, the lifetime of plasma facing components, and the retention of tritium in next step Burning Plasma E...

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Section: Pellet Fuellingmentioning

confidence: 52%

Chapter 4: Power and particle control

Divertor¹,

Database²,

Editors³

1999

Nucl. Fusion

282

View full text Add to dashboard Cite

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“…39 The same mechanism has also been shown to be relevant for the expanding cloud of a high beta pellet injected into the core plasma. 117,297 In this regime, the physics governing the midplane filament velocity is independent of that at the foot-points, so the same dynamics also holds for high-b SOL blobs (in the RX-EM regime) that essentially terminate at the X-points. 48 A second effect, in principle unrelated to the first, is the fact the blobs can transport current (as well as particles, energy and momentum).…”

Section: Electromagnetic Effects On Blob-filaments and Elmsmentioning

confidence: 95%

“…V.) Blob dynamics also have much in common with the motion of plasma clouds formed after ablation of injected pellets. 3,87,[115][116][117] …”

Section: A Blob Charge Polarization and Transport Mechanismmentioning

confidence: 99%

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

2011

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A blob-filament (or simply “blob”) is a magnetic-field-aligned plasma structure which is considerably denser than the surrounding background plasma and highly localized in the directions perpendicular to the equilibrium magnetic field B. In experiments and simulations, these intermittent filaments are often formed near the boundary between open and closed field lines, and seem to arise in theory from the saturation process for the dominant edge instabilities and turbulence. Blobs become charge-polarized under the action of an external force which causes unequal drifts on ions and electrons; the resulting polarization-induced E × B drift moves the blobs radially outwards across the scrape-off-layer (SOL). Since confined plasmas generally are subject to radial or outwards expansion forces (e.g., curvature and ∇B forces in toroidal plasmas), blob transport is a general phenomenon occurring in nearly all plasmas. This paper reviews the relationship between the experimental and theoretical results on blob formation, dynamics and transport and assesses the degree to which blob theory and simulations can be compared and validated against experiments.

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“…In that model (similarly to [2]) assumed is the periodical separation of 'detached cloudlet' from the pellet cloud, and the drift of the cloudlet is considered. The main mechanisms of polarization formation and reducing are suggested to be, besides considered in this paper, the inertial force caused by cloud expansion along curved filed lines, pressure equilibration and a shear of magnetic field.…”

Section: B ∇mentioning

confidence: 99%

“…The formation of this electric field is determined by the following factors: plasma acceleration in the LFS direction, Alfven conductivity of the background plasma and compensation of the p V B ∇ currents in different parts of the cloud propagating along the magnetic field [1]. As it is shown in [1][2][3][4], this B E r r × drift is responsible for significant displacement of the ablated material from the magnetic surfaces where the ablation took place towards LFS. This displacement takes place on a time scale of hundreds microseconds, which is of the same order as the pellet lifetime.…”

Section: Introductionmentioning

confidence: 99%