Simple models for the radial and poloidal E × B drifts in the scrape-off layer of a divertor tokamak: Effects on in/out asymmetries

Stangeby, P.C.; Chankin, A.

doi:10.1088/0029-5515/36/7/i02

Cited by 80 publications

(83 citation statements)

References 23 publications

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“…This drift has been discussed in previous articles [10][11][12][13] to explain the in/out asymmetry of tokamak divertors. A brief derivation of the radial drift is given below.…”

Section: Derivation Of Radial Driftmentioning

confidence: 82%

Observations of cold, high density plasma in the private flux region of the Alcator C-Mod divertor

Boswell

Terry

LaBombard

et al. 2001

Journal of Nuclear Materials

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Significant plasma density has been observed in the private flux zone of the Alcator C-Mod tokamak. The behavior of the D γ emission profiles is consistent with the source of the plasma being due to an E× B drift generated by a poloidal temperature gradient. The plasma flux due to this drift is derived and evaluated. A plasma flux into the private flux zone is inferred by measurements of volumetric recombination using a tangentially viewing CCD camera and several spectroscopic views observing the high n-lines of the D o Balmer series. For the case of an attached divertor the inferred plasma flux to the PFZ has a linear scaling with respect to plasma pressure, as is expected from the temperature-gradient-induced, E × B drift.

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“…This drift has been discussed in previous articles [10][11][12][13] to explain the in/out asymmetry of tokamak divertors. A brief derivation of the radial drift is given below.…”

Section: Derivation Of Radial Driftmentioning

confidence: 82%

Observations of cold, high density plasma in the private flux region of the Alcator C-Mod divertor

Boswell

Terry

LaBombard

et al. 2001

Journal of Nuclear Materials

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“…the Pfirsch-Schlüter return current is a direct consequence of these effects. In the scrape-off layer parallel SOL flow can be produced due to the poloidal asymmetry of E r ×B t and ∇p i ×B t drifts [121,122,11].…”

Section: Sol Flow and Classical Drifts Effectsmentioning

confidence: 99%

Chapter 4: Power and particle control

Divertor¹,

Database²,

Editors³

1999

Nucl. Fusion

280

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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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“…This idea extends to the fluid description of fluid behaviour, although not with a 1:1 mapping between single-particle and fluid drift terms. In the scrape-off layer of Tokamaks, cross-field drift motion has been found to explain asymmetries in particle and power fluxes to inner and outer divertor strike points [8,[77][78][79] during experiments where the toroidal magnetic field has been reversed. During such experiments, it has also been noted that scrape-off layer flows are strongly affected [74,80,81] due to parallel flows induced by poloidal and radial drifts.…”

Section: Cross-field Driftsmentioning

confidence: 99%

Characterisation of detached plasmas on the MAST tokamak

Harrison

2011

Journal of Nuclear Materials

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The mitigation of the steady-state heat loading to plasma-facing components in the divertor structures is an essential prerequisite for the operation of next-generation conventional and tight aspect-ratio Tokamaks. Currently, the most attractive means of reducing this heat loading is the so-called "detached" regime, which is the primary focus of this study.This thesis describes work that was carried out on the MAST tokamak to accurately characterise the plasma conditions within divertor plasmas, and to test the validity of those measurements. To assist in this study, an interpretive code, OSM [1], has been upgraded with additional numerical schemes to ascertain the dominant mechanisms governing parallel scrape-off layer transport including flux expansion, dynamic viscosity and cross-field drift motion in attached conditions. It has been found that the invocation of flux expansion, parallel viscosity and diamagnetic drift motion assist the OSM numerical scheme to converge in the presence of (static+dynamic) parallel pressure gradients often observed between the outboard midplane and lower outer divertor leg.It has also been found that the ion pressure, which is currently unknown, could resolve the observed pressure discrepancy.Line-of-sight spectroscopy of high-n Balmer emission lines has been used to ascertain line averaged T e and line integrated n e during the detached phase of MAST discharges with high spatial resolution (≈ 7mm) to determine electron static pressure profiles along flux contours. Furthermore, narrow-bandwidth imaging spectroscopy of D α , D γ , CII and CIII emission during the onset and sustainment of detachment has been carried out with high temporal (5kHz) and spatial (≈ 3mm) resolution. These data have been combined with ion flux measurements to the divertor target plates using embedded Langmuir probes (6-9mm radial resolution) and upstream Thomson scattering measurements of n e , T e . The data was input into the OSM code, coupled with the kinetic neutral transport code EIRENE [2], to check the experimental data set for internal consistency. The experimental data collected has been used to reconstruct the plasma conditions within the detached divertor leg, heavily constrained by experimental data. EIRENE calculations with re-constructed plasma conditions are able to reproduce experimentally observed D γ /D α line emission ratios to within a factor iii iv of 2 within the recombining region. AcknowledgmentsThe work presented in this thesis is the culmination of the work of many people, who I gratefully acknowledge here. Foremost, I thank Dr. Steven Lisgo for his guidance, enthusiasm and assistance over the last 4 years. It is only on reflection that I appreciate how he kept this work on track, whilst encouraging me to explore my own ideas and how doing so has enhanced the quality of the work presented here. Drs. Andrew Kirk and Geoff Fishpool also deserve special thanks for their guidance, and above all, their understanding in the final months of this work. I also owe great thanks to...

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Simple models for the radial and poloidal E × B drifts in the scrape-off layer of a divertor tokamak: Effects on in/out asymmetries

Cited by 80 publications

References 23 publications

Observations of cold, high density plasma in the private flux region of the Alcator C-Mod divertor

Observations of cold, high density plasma in the private flux region of the Alcator C-Mod divertor

Chapter 4: Power and particle control

Characterisation of detached plasmas on the MAST tokamak

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