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TJ-II: Edge – SOL coupling studies using fast cameras and Langmuir probes: role of edge turbulence and radial electric fields: Difference between revisions
TJ-II: Edge – SOL coupling studies using fast cameras and Langmuir probes: role of edge turbulence and radial electric fields (view source)
Revision as of 19:14, 9 January 2021
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Global plasma confinement studies in both ECRH <ref>E. Ascasibar et al., Plasma Phys. Control. Fusion 44 (2020) B307 </ref> and NBI <ref>E. Ascasibar et al., Contrib. Plasma Physics 50 (2010) 594 </ref> plasmas in TJ-II have shown an improvement with density and degradation with heating power [in agreement with the results reported in the present paper. Whether the transition to improve confinement in the passage from ECRH to NBI plasma scenarios is due to the reduction of broadband turbulence or/and the modification in mean radial electric fields and low frequency ZFs structures <ref>U. Losada et al., PPCF submitted (2020)</ref> remains an open question. | Global plasma confinement studies in both ECRH <ref>E. Ascasibar et al., Plasma Phys. Control. Fusion 44 (2020) B307 </ref> and NBI <ref>E. Ascasibar et al., Contrib. Plasma Physics 50 (2010) 594 </ref> plasmas in TJ-II have shown an improvement with density and degradation with heating power [in agreement with the results reported in the present paper. Whether the transition to improve confinement in the passage from ECRH to NBI plasma scenarios is due to the reduction of broadband turbulence or/and the modification in mean radial electric fields and low frequency ZFs structures <ref>U. Losada et al., PPCF submitted (2020)</ref> remains an open question. | ||
In addition, previous studies have addressed the impact of edge radial electric fields (Er) on turbulence propagation and the coupling between the plasma edge and the scrape-off layer (SOL) during electron–ion root transitions where Er is changed in a controlled manner from positive to negative values <ref>G. Grenfell et al., Nucl. Fusion 60 (2020) 014001</ref>. It has been shown that Er does not only affects the radial turbulence correlation length but it is also capable of reducing the propagation of turbulence from the edge into the SOL. So far, edge-SOL coupling has been investigated using edge Langmuir probes. This characterization can be highly improved using the fast cameras in operation in TJ-II <ref>S. Zweben et al., Rev. Sci. Instrum. 88 041101 ( | In addition, previous studies have addressed the impact of edge radial electric fields (Er) on turbulence propagation and the coupling between the plasma edge and the scrape-off layer (SOL) during electron–ion root transitions where Er is changed in a controlled manner from positive to negative values <ref>G. Grenfell et al., Nucl. Fusion 60 (2020) 014001</ref>. It has been shown that Er does not only affects the radial turbulence correlation length but it is also capable of reducing the propagation of turbulence from the edge into the SOL. So far, edge-SOL coupling has been investigated using edge Langmuir probes. This characterization can be highly improved using the fast cameras in operation in TJ-II <ref>S. Zweben et al., Rev. Sci. Instrum. 88 041101 (2017)</ref> and, in a later phase, using an active He gas puffing experimental set-up under development in TJ-II. | ||
A research programme is proposed with two goals: | A research programme is proposed with two goals: | ||