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TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry: Difference between revisions
TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry (view source)
Revision as of 17:15, 16 October 2018
, 16 October 2018→Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)
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== Name and affiliation of proponent == | == Name and affiliation of proponent == | ||
T. Estrada, J. M. García-Regaña, E. Sánchez, D. Carralero, C. Hidalgo, J.L. Velasco | |||
CIEMAT | |||
== Details of contact person at LNF (if applicable) == | == Details of contact person at LNF (if applicable) == | ||
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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)== | ||
Motivation | '''Motivation''' | ||
Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators | Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators <ref>M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375</ref><ref>P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033</ref><ref>E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan</ref> and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field <ref>J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004</ref>. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution <ref>T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502</ref>. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated. | ||
The main results, discussed in | The main results, discussed in <ref>T. Estrada, et al., IAEA FEC (2018)</ref>, can be summarized as follows: | ||
* Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 <ref>J.M. García-Regaña, et al., PPCF 60 (2018) 10402</ref>. | |||
* Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE <ref>E. Sánchez, et al., IAEA FEC (2018)</ref>. | |||
* Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry. | |||
Proposal | '''Proposal''' | ||
We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table. | We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table. | ||
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one. | We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one. | ||
{| class="wikitable sortable" border="1" cellpadding="2" cellspacing="0" | |||
|+ | |||
|- style="background:#FFDEAD;" | |||
! Config. !! Rax (0º) !! -Zlim(m) !! ι0 !! ιa !! Well(%) !! ripp_axis !! ripp_edge !! a(cm) !! V(m3) | |||
|- | |||
| 100_44_64 || 1.739 || 0.362 || 1.551 || 1.650 || 2.390 || 1.900 || 37.600 || 20.64 || 1.0976 | |||
|- | |||
| 071_44_52 || 1.722 || 0.319 || 1.549 || 1.649 || 3.200 || 1.500 || 29.400 || 17.37 || 0.7575 | |||
|- | |||
| 054_43_45 || 1.709 || 0.288 || 1.543 || 1.648 || 3.200 || ------- || ------- || 14.63 || 0.5315 | |||
|- | |||
| 039_42_38 || 1.699 || 0.261 || 1.549 || 1.674 || 3.000 || 2.900 || 20.000 || 12.35 || 0.3741 | |||
|} | |||
== If applicable, International or National funding project or entity == | |||
Proyecto del Plan Nacional, referencia: FIS2017-88892-P | |||
EUROfusion WP.S1 | |||
== Description of required resources == | == Description of required resources == | ||