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TJ-II:Blobs vs streamers: Difference between revisions
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== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)== | == Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)== | ||
According to a recent suggestion by Chang<ref>C. Chang et al., Self-organization between the neoclassical and turbulent transports across the separatrix surface, resulting in the regulation of the divertor heat-load width, [https://users.euro-fusion.org/repository/pinboard/EFDA-JET/conference/59091_chang.c-th-d-synopsis2.pdf Synopsis for IAEA Conference (2018)]</ref>, turbulence in the edge can be of 'blob type' or 'streamer type'. | According to a recent suggestion by Chang<ref>C. Chang et al., Self-organization between the neoclassical and turbulent transports across the separatrix surface, resulting in the regulation of the divertor heat-load width, [https://users.euro-fusion.org/repository/pinboard/EFDA-JET/conference/59091_chang.c-th-d-synopsis2.pdf Synopsis for IAEA Conference (2018)]</ref>, turbulence in the edge can be of 'blob type' or 'streamer type'. | ||
Chang states: ‘A weak mean <math> E | Chang states: ‘A weak mean <math> E \times B</math> shear, due to the small <math>\rho_i/L</math> effect, allows the formation of the streamer type turbulence.’ | ||
We propose studying this effect, not by varying <math>B</math>, but rather by varying <math>E</math>. To do so, we will scan the edge <math>E_r</math> from negative to positive (crossing zero), either by biasing or by varying the mean density near the spontaneous transition value (<math>n_e \simeq 0.6 | We propose studying this effect, not by varying <math>B</math>, but rather by varying <math>E</math>. To do so, we will scan the edge <math>E_r</math> from negative to positive (crossing zero), either by biasing or by varying the mean density near the spontaneous transition value (<math>n_e \simeq 0.6 \cdot 10^{19}</math>). Near zero Er, transport across the LCFS should be more streamer-like. | ||
Measurements to make: In this scan, we will measure: Isat decay length in SOL (if possible - this may require several discharges), and <math>\omega_S</math>.<ref>P. Manz, T. Ribeiro, B. Scott, G. Birkenmeier, D. Carralero, G. Fuchert, S. Müller, H. Müller, U. Stroth, and E. Wolfrum. Origin and turbulence spreading of plasma blobs. [[doi:10.1063/1.4908272|Phys. Plasmas, 22:022308, 2015]]</ref> | Measurements to make: In this scan, we will measure: Isat decay length in SOL (if possible - this may require several discharges), and <math>\omega_S</math>.<ref>P. Manz, T. Ribeiro, B. Scott, G. Birkenmeier, D. Carralero, G. Fuchert, S. Müller, H. Müller, U. Stroth, and E. Wolfrum. Origin and turbulence spreading of plasma blobs. [[doi:10.1063/1.4908272|Phys. Plasmas, 22:022308, 2015]]</ref> | ||