TJ-II: Why fast reaction of plasma fluctuations to ECRH ?

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Experimental campaign

2019 Autumn

Proposal title

Why fast reaction of plasma fluctuations to ECRH?

Name and affiliation of proponent

CIEMAT (Igor Voldiner, Boudewijn van Milligen, Ulises Losada, Marian Ochando, Carlos Hidalgo) and Croatian Research Group

Details of contact person at LNF

If applicable, enter contact person here or write N/A

Description of the activity

Why do ERCH/ ICRH avoid core impurity accumulation?. Significant progress has been reported regarding the physics understanding of empirical actuators like core heating to avoid impurity accumulation, including the following mechanisms: 1) A reduction of the background density gradient, leading to a reduction of the inward (neoclassical) convection of impurities; 2) An increase of turbulent transport; 3) The amplification of core temperature screening which would be relevant in core alpha-heating regimes; 4) The development of core plasma potential flux surface asymmetries.

Why fast reaction of plasma fluctuations to ECRH?. This is the (challenging) question that we want to answer including experiments in TJ-II 2019 / 20, data analysis and model validation.

From the theoretical perpective we should consider different mechanisms: The role of phase space driven instabilities [1]; role of fast particles on MHD stability [2]; the role of plasma gradient driven instabilities [3] and the influence of ECRH in the turbulent drive [4].

From the experimental perspective the goal is the investigation and characterization of the influence of ECRH on / off power heating in the dynamics of edge & core fluctuations and transport in the TJ-II stellarator, including: 1) Level of fluctuations, 2) Phase relation between density and potential fluctuations, 3) Turbulent ExB transport.

International or National funding project or entity

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Description of required resources

Required resources:

  • Number of plasma discharges or days of operation: two days
  • Essential diagnostic systems: Edge & core turbulence and transport studies
  • Type of plasmas (heating configuration): ECRH power on-off scan [100 – 600 kW] in H vs He plasmas
  • 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)


  1. S. Itoh and K. Itoh Scientific Reports 2, 860 (2012)
  2. L. García et al., Physics of Plasmas 23, 062319 (2016)
  3. E. Sánchez et al., Nucl Fusion 59, 076029 (2019)
  4. X. Wang et al., Nucl Fusion 57, 57, 116046 (2017)

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