Atomic and Molecular Collisions in the Plasma Boundary

Harrison, Mark

doi:10.1007/978-1-4757-0067-1_7

Cited by 16 publications

(20 citation statements)

References 53 publications

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“…Noting that ξ is only a relatively weak function of n and T [74], Eq. (66) provides a relation between the upstream density n det S at complete detachment and the device and discharge parameters B t , L X πq ψ R, and q ⊥ , respectively.…”

Section: Upstream Regionmentioning

confidence: 99%

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Plasma Edge Physics with B2‐Eirene

Schneider

Bonnin

Borraß

et al. 2006

Contrib. Plasma Phys.

477

426

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The B2‐Eirene code package was developed to give better insight into the physics in the scrape‐off layer (SOL), which is defined as the region of open field‐lines intersecting walls. The SOL is characterised by the competition of parallel and perpendicular transport defining by this a 2D system. The description of the plasma‐wall interaction due to the existence of walls and atomic processes are necessary ingredients for an understanding of the scrape‐off layer. This paper concentrates on understanding the basic physics by combining the results of the code with experiments and analytical models or estimates. This work will mainly focus on divertor tokamaks, but most of the arguments and principles can be easily adapted also to other concepts like island divertors in stellarators or limiter devices. The paper presents the basic equations for the plasma transport and the basic models for the neutral transport. This defines the basic ingredients for the SOLPS (Scrape‐Off Layer Plasma Simulator) code package. A first level of understanding is approached for pure hydrogenic plasmas based both on simple models and simulations with B2‐Eirene neglecting drifts and currents. The influence of neutral transport on the different operation regimes is here the main topic. This will finish with time‐dependent phenomena for the pure plasma, so‐called Edge Localised Modes (ELMs). Then, the influence of impurities on the SOL plasma is discussed. For the understanding of impurity physics in the SOL one needs a rather complex combination of different aspects. The impurity production process has to be understood, then the effects of impurities in terms of radiation losses have to be included and finally impurity transport is necessary. This will be introduced with rising complexity starting with simple estimates, analysing then the detailed parallel force balance and the flow pattern of impurities. Using this, impurity compression and radiation instabilities will be studied. This part ends, combining all the elements introduced before, with specific, detailed results from different machines. Then, the effect of drifts and currents is introduced and their consequences presented. Finally, some work on deriving scaling laws for the anomalous turbulent transport based on automatic edge transport code fitting procedures will be described. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Upstream Regionmentioning

confidence: 99%

“…* is the mean energy consumed per ionisation event and c s is the ion sound speed (c s = (µT i + T e )/m, µ = 1, T i = T e ) [74]. In particular,…”

Section: Upstream Regionmentioning

confidence: 99%

Plasma Edge Physics with B2‐Eirene

Schneider

Bonnin

Borraß

et al. 2006

Contrib. Plasma Phys.

477

426

View full text Add to dashboard Cite

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“…If it is assumed that this concentration arises from an effective formation rate in competition with electron impact ionisation (which is the main destruction mechanism), then it is straightforward to show (Harrison 1985) that the cross field particle diffusion coefficient may be written where Ne is in cmd3, T is in eV and Deff is in cm2 s-l with cimp = Nimp/ N e , the impurity concentration. Values of De, are given in table 4.…”

Section: L70mentioning

confidence: 99%

The search for an atomic cause of anomalous diffusion in fusion plasmas

Greenland

1988

J. Phys. B: At. Mol. Opt. Phys.

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“…(2) has received little attention, but there is evidence (Harrison 1986) that the cross section can be large, and it has been suggested (Pease 1986) that this process may contribute a source of neutral H in the centre of a fusion plasma, where electron impact maintains a population of excited impurity ions. Since this neutral H can cross the confining magnetic field lines, charge capture from excited impurities makes a contribution to cross-field transport.…”

Section: Introductionmentioning

confidence: 99%

Excited impurity species and plasma transport

Greenland

Harrison

1988

J. Phys. B: At. Mol. Opt. Phys.

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The authors discuss the role of charge exchange in collisions between protons and thermally excited impurity ions in modifying the cross-field transport of hydrogen. It is assumed that electron collisions with partially stripped impurity ions maintain a population of highly excited, highly charged ions, which produce neutral hydrogen by charge exchange with plasma protons, and that the diffusion of this hydrogen modifies cross-field transport of both electrons and protons. This effect is shown to be small. In order to discuss this phenomenon, empirical fits to a large number of effective rate coefficients were used, and these are recorded in an appendix.

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Atomic and Molecular Collisions in the Plasma Boundary

Cited by 16 publications

References 53 publications

Plasma Edge Physics with B2‐Eirene

Plasma Edge Physics with B2‐Eirene

The search for an atomic cause of anomalous diffusion in fusion plasmas

Excited impurity species and plasma transport

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