TJ-II:Impurity density and potential asymmetries
Experimental campaign
2017 Spring
Proposal title
Impurity density and potential asymmetries
Name and affiliation of proponent
Jose M García Regaña
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 (syntax error): {\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.
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)