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TJ-II: Influence of edge radial electric fields on impurity transport: Difference between revisions
TJ-II: Influence of edge radial electric fields on impurity transport (view source)
Revision as of 18:53, 20 January 2022
, 20 January 2022→Description of the activity
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Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator. | Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator. | ||
Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition. | Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition and in the proximity to de NBI density limit. | ||
The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner. | The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner. | ||