TJ-II:Investigation of turbulence spreading and information transfer in the TJ-II stellarator

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Experimental campaign

2017 Spring

Proposal title

Investigation of turbulence spreading and information transfer in the TJ-II stellarator

Name and affiliation of proponent

G. Grenfell1, B. van Milligen1, U. Losada1, Wu Ting1,7, A. Chmyga2, G.N. Deshko2, L.G. Eliseev3, C. Hidalgo1, P. O. Khabanov, S.M. Khrebtov2, A.D. Komarov2, A.S. Kozachek2, L.I. Krupnik2, Bing Liu1, A.V. Melnikov3,4, J.L. de Pablos1, Monica Spolaore5, Ufimtsev6, V.N. Zenin3, A.I. Zhezhera2

  1. Fusion National Laboratory, CIEMAT, 28040, Madrid, Spain
  2. Institute of Plasma Physics, NSC KIPT, 310108, Kharkov, Ukraine
  3. National Research Centre ‘Kurchatov Institute’, 123182, Moscow, Russia
  4. National Research Nuclear University MEPhI, 115409, Moscow, Russia
  5. Consorzio RFX , Padova, Italy
  6. Moscow State University, 119991, Moscow, Russia
  7. Southwestern Institute of Physics, Chengdu, Sichuan 610041, China

Details of contact person at LNF (if applicable)

Boudewijn van Milligen

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

Motivation. Turbulence spreading or radial transport of turbulence energy occurs because inhomogeneous turbulence generically tends to redistribute its energy from regions where dominant free energy sources are located to regions which do not access external free energy sources directly. This causes the so call spreading of turbulence from regions that are strongly driven (i.e., unstable regions) into regions which are only weakly driven [1].

Plasma edges in stellarators can be quite different than edges in tokamaks. In particular, configurations with the long connection lengths in stellarators means that cross-field transport can compete with parallel transport along open field lines. Clarifying whether the SOL width is dominated by local effects at the SOL region or/and by transport driven in the plasma edge is a relevant question. Recent experiments in the TJ-II stellarator have shown that SOL profiles are coupled with edge plasma parameters and that the strength of this coupling depends on the magnitude of the edge shearing rate and level of edge fluctuations. Consequently optimizing SOL power exhaust would require considering transport in the edge region. [2]

Experimental plan and goals. The goal of this research work is to investigate the influence of isotope mass and sheared flows on the coupling between core / edge and SOL regions including the following actions:

  • Characterization of the structure of edge ExB flows and edge turbulence during the electron-ion root transition.
  • Investigation of the influence of edge ExB sheared flows and turbulence on the strength of Edge-SOL coupling in H and D plasmas.
  • Propagation of edge / core perturbations (i.e. pellets / ECRH modulation / biasing) on the SOL in plasma regimes with different edge sheared flows.
  • Analysis of these edge/core perturbations using the Transfer Entropy [3], to quantify the flow of information from the edge to the SOL
  • Characterization of core-edge-SOL turbulence spreading.

Key diagnostics: Edge probes to characterize edge-SOL coupling and Dual HIBP to characterize core – edge coupling

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

  1. P. Manz et al., Phys. Plasmas 22 (2015) 022308 and references therein
  2. Wu Ting et al., Master Thesis 2016
  3. B. Ph. van Milligen et al., Nucl. Fusion 54 (2014), 023011 and Phys. Plasmas 23, 072305 (2016)

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