TJ-II:Measurements of radial correlation length and tilting of turbulent eddies by Radial Correlation Doppler Reflectometry

Experimental campaign

2017 Spring

Proposal title

Measurements of radial correlation length and tilting of turbulent eddies by Radial Correlation Doppler Reflectometry

Name and affiliation of proponent

J.R. Pinzón and T. Happel. Max-Planck-Institut für Plasmaphysik, Garching

Details of contact person at LNF (if applicable)

Teresa Estrada

Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)

To properly characterize the turbulence, the knowledge of the radial and poloidal correlation lengths is insufficient; information on the elongation and tilting is also needed in order to compare with models and gyrokinetic results. Simulations have demonstrated that correlation lengths, elongation and tilting could be obtained using cross-correlation techniques applied to a synthetic Radial Correlation Doppler reflectometer [1], however the role of other physical phenomena (small angle scattering [2] and non-linear diagnostic response [3]) has to be further investigated in experiments. Objectives: In order to validate a recently developed model [1], a set of experiments is proposed to obtain radial correlation measurements for different reflectometry settings, probing beam angle and frequencies, providing a scan of the radial position and the probed perpendicular wavenumber. Fine scans are required in order to compare with 2D Full Wave simulations results and to determine correlation lengths, elongation and tilting. The measurements will be repeated under different plasma conditions changing parameter that may influence the tilting of the turbulent eddies. OH current experiments modifying the ι profile and consequently the tilting (continuation of experiments performed 2016 March 3rd); plasmas in electron and in ion root to study the tilting with positive and negative Er (continuation of experiments performed 2016 December 21st); DC biasing experiments with positive and negative polarization voltage; and finally measurements in H and D plasmas are also proposed in order to study the isotope effect on the correlation length and tilting. The results will be compared with those obtained in the simulations and similar experiments in AUG. Proposal: H and/or D ECRH heated plasmas in the standard configuration 100_44_64, with 10 successful reproducible shots per plasma configuration (OH current, bias voltage) are needed in order to scan all the reflectometer parameters.

[1] J.R. Pinzón et al., “Modeling of Radial Correlation Doppler Reflectometry response to density turbulence wave number spectra” 12th International Reflectometry Workshop, Jülich, Germany (2015)

[2] E. Gusakov, M. Irzak and A. Popov. Plasma Phys. Control. Fusion 56 (2014) 05009

[3] E. Gusakov and A. Popov. Plasma Phys. Control. Fusion 46 (2004) 1393-1408

If applicable, International or National funding project or entity

International Funding Project: AWP15-ENR-01/IPP-02

National Funding Project ENE2013-48109-P

Description of required resources

Required resources:

• Number of plasma discharges or days of operation: at least two experimental days are required
• Essential diagnostic systems:Microwave interferometer, AM and Doppler reflectometers, Thomson scattering, ECE, Hα detectors, SXR, bolometry, CX, Magnetics
• Type of plasmas (heating configuration): Mainly ECH plasmas
• Specific requirements on wall conditioning if any: Relatively fresh Li for a good density control
• External users: need a local computer account for data access: no
• Any external equipment to be integrated? Provide description and integration needs:

Preferred dates and degree of flexibility

Preferred dates:

between 20-02-2017 and 03-03-2017

between 22-03-2017 and 22-04-2017

References

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