E × B Flux Driven Detachment Bifurcation in the DIII-D Tokamak

dc.contributorAalto Universityen
dc.contributor.authorJärvinen, Aaroen_US
dc.contributor.authorAllen, S.L.en_US
dc.contributor.authorEldon, D.en_US
dc.contributor.authorFenstermacher, M.E.en_US
dc.contributor.authorGroth, Mathiasen_US
dc.contributor.authorHill, David Nen_US
dc.contributor.authorLeonard, A.W.en_US
dc.contributor.authorMcLean, A.G.en_US
dc.contributor.authorPorter, G.D.en_US
dc.contributor.authorRognlien, T.D.en_US
dc.contributor.authorSamuell, C. M.en_US
dc.contributor.authorWang, Huiqianen_US
dc.contributor.departmentDepartment of Applied Physicsen
dc.contributor.groupauthorFusion and Plasma Physicsen
dc.contributor.organizationLawrence Livermore National Laboratoryen_US
dc.contributor.organizationGeneral Atomicsen_US
dc.contributor.organizationOak Ridge Associated Universitiesen_US
dc.description.abstractA bifurcative step transition from low-density, high-temperature, attached divertor conditions to high-density, low-temperature, detached divertor conditions is experimentally observed in DIII-D tokamak plasmas as density is increased. The step transition is only observed in the high confinement mode and only when the B × ∇B drift is directed towards the divertor. This work reports for the first time a theoretical explanation and numerical simulations that qualitatively reproduce this bifurcation and its dependence on the toroidal field direction. According to the model, the bifurcation is primarily driven by the interdependence of the E × B-drift fluxes, divertor electric potential structure, and divertor conditions. In the attached conditions, strong potential gradients in the low field side (LFS) divertor drive E × B-drift flux towards the high field side divertor, reinforcing low density, high temperature conditions in the LFS divertor leg. At the onset of detachment, reduction in the potential gradients in the LFS divertor leg reduce the E × B-drift flux as well, such that the divertor plasma evolves nonlinearly to high density, strongly detached conditions. Experimental estimates of the E × B-drift fluxes, based on divertor Thomson scattering measurements, and their dependence on the divertor conditions are qualitatively consistent with the numerical predictions. The implications for divertor power exhaust and detachment control in the next step fusion devices are discussed.en
dc.description.versionPeer revieweden
dc.identifier.citationJärvinen, A, Allen, S L, Eldon, D, Fenstermacher, M E, Groth, M, Hill, D N, Leonard, A W, McLean, A G, Porter, G D, Rognlien, T D, Samuell, C M & Wang, H 2018, ' E × B Flux Driven Detachment Bifurcation in the DIII-D Tokamak ', Physical Review Letters, vol. 121, no. 7, 075001, pp. 1-4 . https://doi.org/10.1103/PhysRevLett.121.075001en
dc.identifier.otherPURE UUID: acff7c50-ebae-432f-ba30-1da940859883en_US
dc.identifier.otherPURE ITEMURL: https://research.aalto.fi/en/publications/acff7c50-ebae-432f-ba30-1da940859883en_US
dc.identifier.otherPURE FILEURL: https://research.aalto.fi/files/28689967/PhysRevLett.121.075001.pdfen_US
dc.relation.ispartofseriesPHYSICAL REVIEW LETTERSen
dc.relation.ispartofseriesVolume 121, issue 7en
dc.subject.keywordplasma driftsen_US
dc.titleE × B Flux Driven Detachment Bifurcation in the DIII-D Tokamaken
dc.typeA1 Alkuperäisartikkeli tieteellisessä aikakauslehdessäfi