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 | <ref>H. Mynick ''Calculation of the poloidal ambipolar field in a stellarator | ||
with | and its effect on transport'' Phys. Fluids '''27'''(8) 2086 (1984)</ref>, usually denoted by $\Phi_1=\Phi_1(\theta,\phi)$, | ||
When this is taken into account the equilibrium density of the different species | with <math>\theta</math> and </math>\phi</math> the poloidal and toroidal angular coordinates. | ||
varies according to their adiabatic response and can be written as: | 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}=\left<n\right>\exp\left(-Z_{a}e\Phi_1/T_{a}\right)</math>, with | |||
have shown that | </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>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> | |||
have shown that </math>e\Phi_1/T_{a}</math> can take values from $O(0.01)$ to $O(0.1)$. 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. | ||
== If applicable, International or National funding project or entity == | == If applicable, International or National funding project or entity == | ||
Revision as of 16:14, 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 $\Phi_1=\Phi_1(\theta,\phi)$, with 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 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 [2] [3] [4] have shown that </math>e\Phi_1/T_{a}</math> can take values from $O(0.01)$ to $O(0.1)$. 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 </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 </math>Z</math>. 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)