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Jose.regana: Created page with "== Experimental campaign == 2017 Spring == Proposal title == '''Potential asymmetries at low magnetic field''' == Name and affiliation of proponent == José M García Regañ..."

2017-01-27T14:07:28Z

Created page with "== Experimental campaign == 2017 Spring == Proposal title == '''Potential asymmetries at low magnetic field''' == Name and affiliation of proponent == José M García Regañ..."

New page

== Experimental campaign ==
2017 Spring

== Proposal title ==
'''Potential asymmetries at low magnetic field'''

== Name and affiliation of proponent ==
José M García Regaña1, José Luis Velasco1, J. A. Alonso 1, I. Calvo 1, C. Hidalgo1, Bing Liu1, ...

== Details of contact person at LNF (if applicable) ==
Enter contact person here or N/A

== 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 TJ-II NBI plasmas
<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>
drifts scale both with <math>B^{-1}</math>, see e.g.
<ref>D. D.-Ho and R. M. Kulsrud '' ''Neoclassical Transport in Stellarators'' Phys. Fluids '''30''' (2) 1987</ref>,
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 are required, scanning the electron temperature at the outer region is required.

== If applicable, International or National funding project or entity ==
Enter funding here or N/A

== Description of required resources ==
== Description of required resources ==

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 application of biasing potential at the outer core region is necessitated to measure the floating potential difference.
* 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 time evolution of the electron temperature profile <math>T_{e}(r,t)</math> with Electron Cyclotron Emission (ECE), when available, calibrated with TS.
* The time evolution of the ion temperature in the core and in an outer radial position <math>T_i(r/a\sim 0.2,t)</math> and <math>T_i(r/a\sim 0.8,t)</math> with the Neutral Particle Analyzer (NPA).
* The time evolution of the radial electric field at the mid-outer region (<math>r/a\sim 0.5-0.8</math>) with reflectometry, if possible.
* The time evolution of the electrostatic potential in the mid-outer region <math>\Phi(r/a\sim0.7,t)</math> with the double Heavy Ion Beam Probe (HIBP).

Other requirements:

* One successful day of operation.
* Background standard configuration with magnetic field rescaled to <math>B\sim 0.6 </math> T.
* NBI heating. No ECRH heating.

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)

== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals]]

TJ-II:Potential Assymetries at low magnetic field - Revision history

Admin at 08:41, 18 February 2021

Admin at 08:40, 18 February 2021

Jose.regana: Created page with "== Experimental campaign == 2017 Spring == Proposal title == '''Potential asymmetries at low magnetic field''' == Name and affiliation of proponent == José M García Regañ..."