TJ-II:Turbulence spreading and ECRH modulation experiments in the TJ-II stellarator

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Experimental campaign

2018 Autumn

Proposal title

Turbulence spreading and ECRH modulation experiments in the TJ-II stellarator

Name and affiliation of proponent

Gustavo Grenfell, Boudewijn van Milligen, Teresa Estrada, Álvaro Cappa, J.L. de Pablos, HIBP Team

Details of contact person at LNF (if applicable)

Enter contact person here or N/A

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

Radial transport of turbulent energy occurs naturally as a consequence of the redistribution of fluctuation energy from regions with dominant free energy sources to adjacent regions without or with less accentuated free energy sources. The spreading of turbulence therefore involves transport from strongly driven (i.e., unstable regions) to weakly driven regions. Evidence of turbulence spreading has been previously reported in the TJ-II gradient region. [1][2]

The goal of this proposal is to study the impact of ECRH power modulation in the core region on plasma fluctuations outside the core region, and studying the propagation of variations in the turbulence amplitude from the core (using HIBP) to the gradient region (Doppler reflectometer) and the edge (Langmuir probes). By applying fast ECRH modulation (of the order of 10 kHz), we will reduce the impact of (diffusive) transport on the results as much as possible.

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: 2 days
  • Essential diagnostic systems: HIBP, Doppler reflectometer, Langmuir probes
  • Type of plasmas (heating configuration): Fast ECRH power modulation to characterize the propagation of fluctuations from the core to the plasma boundary region.
  • 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: second half of December (planned visit of Gustavo)

References

  1. T. Estrada et al., NF 51 (2011) 032001
  2. G. Grenfell et al., NF 2018 submitted

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