TJ-II:Impurity density and potential asymmetries: Difference between revisions
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Neoclassical theory predicts a non-constant portion of the electrostatic potential over the flux surfaces | Neoclassical theory predicts a non-constant portion of the electrostatic potential over the flux surfaces | ||
<ref>H. Mynick ''Calculation of the poloidal ambipolar field in a stellarator | <ref>H. Mynick ''Calculation of the poloidal ambipolar field in a stellarator | ||
and its effect on transport'' Phys. Fluids '''27'''(8) 2086 (1984)</ref>, usually denoted by | and its effect on transport'' Phys. Fluids '''27'''(8) 2086 (1984)</ref>, usually denoted by <math>\Phi_1=\Phi_1(\theta,\phi)</math>, | ||
with <math>\theta</math> and < | 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: < | varies according to their adiabatic response and can be written as: <math>n_{a0}=\left<n\right>\exp\left(-Z_{a}e\Phi_1/T_{a}\right)</math>, with | ||
< | <math>\left<...\right></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> | ||
<ref>J M Garcı́a-Regaña ''et al.'' ''Electrostatic potential variation on the flux surface and its impact on impurity transport'' Nuclear Fusion submitted (2017)</ref> | <ref>J M Garcı́a-Regaña ''et al.'' ''Electrostatic potential variation on the flux surface and its impact on impurity transport'' Nuclear Fusion submitted (2017)</ref> | ||
have shown that < | have shown that <math>e\Phi_1/T_{a}</math> can take values from <math>O(0.01)</math> to <math>O(0.1)</math>. Variations are predicted to be | ||
larger at the outer radii than at the inner core, and stronger in ECRH plasmas than in NBI plasmas. Under | larger at the outer radii than at the inner core, and stronger in ECRH plasmas than in NBI plasmas. Under | ||
conditions with large < | conditions with large <math>\Phi_1</math> the impurities of moderate to high <math>Z</math> should experience strong variations of their densities over the flux surfaces, | ||
increasing with < | increasing with <math>Z</math>. | ||
These, in turn, should result in an anisotropic radiation over each flux surface and consequently | These, in turn, should result in an anisotropic radiation over each flux surface and consequently | ||
a radially asymmetric radiation pattern should follow. | a radially asymmetric radiation pattern should follow. | ||
Revision as of 16:17, 24 January 2017
Experimental campaign
2017 Spring
Proposal title
Impurity density and potential asymmetries
Name and affiliation of proponent
Jose M Garc\'ia Rega\~na
Details of contact person at LNF (if applicable)
Jose M Garc\'ia Rega\~na
Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)
Neoclassical theory predicts a non-constant portion of the electrostatic potential over the flux surfaces [1], usually denoted by , with and the poloidal and toroidal angular coordinates. 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: Failed to parse (syntax error): {\displaystyle n_{a0}=\left<n\right>\exp\left(-Z_{a}e\Phi_1/T_{a}\right)} , with Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \left<...\right>} the flux-surface-average. In TJ-II plasmas experiments and simulations [2] [3] [4] have shown that can take values from to . Variations are predicted to be larger at the outer radii than at the inner core, and stronger in ECRH plasmas than in NBI plasmas. Under conditions with large the impurities of moderate to high should experience strong variations of their densities over the flux surfaces, increasing with . These, in turn, should result in an anisotropic radiation over each flux surface and consequently a radially asymmetric radiation pattern should follow.
If applicable, International or National funding project or entity
Enter funding here or N/A
Description of required resources
Required resources:
- Number of plasma discharges or days of operation:
- Essential diagnostic systems:
- Type of plasmas (heating configuration):
- Specific requirements on wall conditioning if any:
- External users: need a local computer account for data access: yes/no
- Any external equipment to be integrated? Provide description and integration needs:
Preferred dates and degree of flexibility
Preferred dates: (format dd-mm-yyyy)
References
- ↑ H. Mynick Calculation of the poloidal ambipolar field in a stellarator and its effect on transport Phys. Fluids 27(8) 2086 (1984)
- ↑ M A Pedrosa et al., Electrostatic potential variations along flux surfaces in stellarators Nucl. Fusion 55 052001 (2015)
- ↑ B Liu et al. Direct experimental evidence of potential asymmetry in magnetic flux surfaces in stellarators to be submitted (2017)
- ↑ J M Garcı́a-Regaña et al. Electrostatic potential variation on the flux surface and its impact on impurity transport Nuclear Fusion submitted (2017)