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 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 , usually denoted by $\Phi_1=\Phi_1(\theta,\phi)$, with $\theta$ and $\phi$ 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: $n_{a0}=\left<n\right>\exp\left(-Z_{a}e\Phi_1/T_{a}\right)$, with $\left<...\right>$ the flux-surface-average. In TJ-II plasmas experiments and simulations have shown that $e\Phi_1/T_{a}$ 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 $\Phi_1$ the impurities of moderate to high $Z$ should experience strong variations of their densities over the flux surfaces, increasing with $Z$. 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:
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• 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

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References

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