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TJ-II:Potential asymmetries at low magnetic field: Difference between revisions
TJ-II:Potential asymmetries at low magnetic field (view source)
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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)== | ||
'''Background''': Recent measurements in TJ-II have shown a qualitative good agreement between numerically predicted and measured potential variations in | '''Background''': Recent measurements in TJ-II have shown a qualitative good agreement between numerically predicted and measured potential variations in NBI ion-root conditions | ||
<ref>B Liu ''et al.'' ''Direct experimental evidence of potential asymmetry in magnetic flux surfaces in stellarators'' to be submitted (2017) </ref>. | <ref>B Liu ''et al.'' ''Direct experimental evidence of potential asymmetry in magnetic flux surfaces in stellarators'' to be submitted (2017) </ref>. | ||
Experiments and simulations have shown similar scaling with the electron temperature <math>T_{e}</math> and comparable phase difference between the measured and calculated values of the potential at two distant positions of the same flux surface. Heuristically, these variations can be shown to scale independently on <math>B</math> since the magnetic and <math>E_r\times B</math> | Experiments and simulations have shown similar scaling with the electron temperature <math>T_{e}</math> and comparable phase difference between the measured and calculated values of the potential at two distant positions of the same flux surface. Heuristically, these variations can be shown to scale independently on <math>B</math> since the magnetic and <math>E_r\times B</math> | ||
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unless that <math>E_{r}</math> varies noticeably with <math>B</math>. Here <math>E_{r}</math> and <math>B</math> are the ambipolar neoclassical electric field and magnetic field modulus respectively. | unless that <math>E_{r}</math> varies noticeably with <math>B</math>. Here <math>E_{r}</math> and <math>B</math> are the ambipolar neoclassical electric field and magnetic field modulus respectively. | ||
'''Objective''': the present experiment, which aims at assessing the scaling of <math>\Phi_1</math> with <math>B</math> and compare with theory, follows in essence the approach and techniques reported in ref. [1]. Hence, similar NBI plasma parameters as those in the past experiments | '''Objective''': the present experiment, which aims at assessing the scaling of <math>\Phi_1</math> with <math>B</math> (or the lack of it) and compare with theory, follows in essence the approach and techniques reported in ref. [1]. Hence, similar NBI plasma parameters as those in the past experiments scanning the electron temperature at the outer region are required. | ||
== If applicable, International or National funding project or entity == | == If applicable, International or National funding project or entity == | ||
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The signals and systems required to carry out the analysis are: | The signals and systems required to carry out the analysis are: | ||
* The time evolution of the plasma floating potential at the outer core region (<math>r/a\sim 0.9</math>), measured with the double probe system. | * The time evolution of the plasma floating potential <math>\phi_f(t)</math> at the outer core region (<math>r/a\sim 0.9</math>), measured with the double Langmuir probe system. | ||
* The application of biasing potential at the outer core region is necessitated to | * The application of biasing potential at the outer core region is necessitated to quantify <math>\Delta\phi_f</math>. | ||
* The time evolution of the line-averaged density <math>\left<n_e(t)\right></math> with interferometry. | * The time evolution of the line-averaged density <math>\left<n_e(t)\right></math> with interferometry. | ||
* The radial profiles of electron density <math>n_{e}(r, t_0)</math> and temperature at one time instant <math>t_0</math> using Thomson Scattering (TS). | * The radial profiles of electron density <math>n_{e}(r, t_0)</math> and temperature at one time instant <math>t_0</math> using Thomson Scattering (TS). | ||
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[[Category:TJ-II internal documents]] | [[Category:TJ-II internal documents]] | ||
[[Category:TJ-II experimental proposals]] | [[Category:TJ-II experimental proposals 2017]] | ||