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TJ-II:Impurity density and potential asymmetries: Difference between revisions
TJ-II:Impurity density and potential asymmetries (view source)
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== Experimental campaign == | == Experimental campaign == | ||
2017 Spring | 2017 Spring | ||
[[File:Photo_2018-07-20_09-32-57.jpg |thumb|right|500px| Figure 1. | |||
Numerical vs Experiment electron-root #45477 discharge: | |||
(a,b) Numerical impurity density asymmetry parameter <math>\alpha_{nZ}</math> and the | |||
experimental radiation asymmetry parameter <math>\alpha_{rad}</math> respectively at the toroidal plane | |||
<math>\phi=14.5^{\circ}</math> that corresponds the SXR toroidal measurement plane. (c,d) Numerical | |||
impurity density asymmetry parameter <math>\alpha_{nZ}</math> and the experimental radiation asymmetry | |||
parameter <math>\alpha_{rad}</math> respectively at the toroidal plane <math>\phi=75.5^{\circ}</math> that corresponds | |||
the Bolometery toroidal position. Note the numerical and experimental scale sare | |||
the same <math>[-0.38, 0.38]</math>. Since neon impurities were puffed at trave levels during the discharges, the numerical | |||
results in (a,c) have considered <math>Z_{I}=10</math>, i.e. they have assumed fully ionization of Ne on the whole | |||
effective radius <ref> M. Ezzat ''Advanced neoclassical impurity transport | |||
modelling with experimental comparison for TJ-II'' Master Thesis (2018)</ref>]] | |||
[[File:Photo_2018-07-20_09-33-36.jpg |thumb|right|500px| Figure 2. Same as in figure 1. but considering the ion-root discharge #45469 <ref> M. Ezzat ''Advanced neoclassical impurity transport | |||
modelling with experimental comparison for TJ-II'' Master Thesis (2018)</ref>]] | |||
== Proposal title == | == Proposal title == | ||
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== Name and affiliation of proponent == | == Name and affiliation of proponent == | ||
José M García Regaña<sup>1</sup>, M. Ezzat<sup>1</sup>, B. van Milligen<sup>1</sup>, M. A. Ochando <sup>1</sup>, F. Medina<sup>1</sup>, | |||
José Luis Velasco<sup>1</sup>, J. A. Alonso <sup>1</sup>, I. Calvo <sup>1</sup>, C. Hidalgo<sup>1</sup>, K. McKarthy<sup>1</sup> | |||
# Fusion National Laboratory, CIEMAT, 28040, Madrid, Spain | |||
== 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)== | ||
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with <math>\theta</math> and <math>\phi</math> the poloidal and toroidal angular coordinates. | with <math>\theta</math> and <math>\phi</math> the poloidal and toroidal angular coordinates. | ||
When this is taken into account the equilibrium density of the different species ''a'' present in the plasma | When this is taken into account the equilibrium density of the different species ''a'' present in the plasma | ||
varies according to their adiabatic response and can be written as: <math>n_{a0}=\ | varies according to their adiabatic response and can be written as: <math>n_{a0}=\langle n\rangle\exp\left(-Z_{a}e\Phi_1/T_{a}\right)</math>, with | ||
<math>\ | <math>\langle...\rangle</math> the flux-surface-average. In TJ-II plasmas experiments and simulations | ||
<ref>M A Pedrosa ''et al.'', ''Electrostatic potential variations along flux surfaces in stellarators'' Nucl. Fusion '''55''' 052001 (2015) </ref> | <ref>M A Pedrosa ''et al.'', ''Electrostatic potential variations along flux surfaces in stellarators'' Nucl. Fusion '''55''' 052001 (2015) </ref> | ||
<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> | ||
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a radially asymmetric radiation pattern should follow. | a radially asymmetric radiation pattern should follow. | ||
In the present experiment the analysis of the radial profiles and time evolution of the plasma emissivity using the TJ-II bolometry | |||
system <ref> M. A. Ochando ''et al.'' ''Up-down and in-out asymmetry monitoring based on broadband radiation detectors'' Fusion Sci. and Technol. '''50''' 313 (2006) </ref> after the inyection | |||
of some selected impurities by gas puffing is proposed. The experiment aims at studying the above-mentioned link between the radially assymetric | |||
emissivity and the measured and predicted <math>\Phi_1</math>. The measurement and evolution of <math>\Phi_1</math> will be tracked | |||
during the discharges using the duplicated Langmuir probe system plasma floating potential measurements. | |||
Numerical calculations of <math>\Phi_1</math> will be carried out with the neoclassical version of the code EUTERPE | |||
at different radial locations. | |||
The application of fluid tools is also foreseen for the comparison between simulations and with the experimental results. | |||
== Description of required resources == | == Description of required resources == | ||
* | The required signals to perform the analysis are: | ||
* | |||
* | * The time evolution of the plasma emissivity radial profile via tomographic reconstructions of the bolometry system signals. | ||
* | * The time evolution of the plasma floating potential at the outer core region (<math>r/a\sim 0.9</math>). | ||
* | * The time evolution of the line-averaged density <math>\langle n_e(t)\rangle</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 resion (<math>r/a\sim 0.7-0.8</math>) with reflectometry. | |||
* 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 constraints regarding the desired experimental conditions are: | |||
* Good reproducibility of the plasma discharges to allow comparison across impurity and charge states <math>Z</math>. Scannig <math>T_e</math> is also considered by the application of different ECH injected power. | |||
* Good stationarity of plasma parameters at the instant where the impurities are injected is required in order to extract the stationary background emissivity from that produced by the injected impurity. Hence the study shall preferably be perform in ECRH plasmas. | |||
== Preferred dates and degree of flexibility == | == Preferred dates and degree of flexibility == | ||
Preferred dates: (format dd-mm-yyyy) | Preferred dates: (format dd-mm-yyyy) | ||
== Results == | |||
== References == | == References == | ||
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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]] | ||