TJ.II:The study of edge turbulence in the presence of ECRH and NBI heating

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Experimental campaign

2019 Autumn

Proposed Title

TJ-II: The study of edge turbulence in the presence of ECRH and NBI heating

Name and affiliation of proponent

Ghassan Antar, American University of Beirut, P.O.Box 11-0236 / Physics Department, Riad El-Solh / Beirut 1107 2020, Lebanon. Email: ga40@aub.edu.lb

Details of contact person at LNF

Kieran J McCarthy

Description of the activity

We wish to investigate the effects of plasma additional heating on edge turbulence. Diagnostics that yield the average edge properties (density and temperature) are required as well as the two Langmuir probes for the fluctuations along with the fast imaging camera. Lately, the comparison between L-mode and NBI-driven H-mode on the ASDEX-Upgrade tokamak has shown no modification in the density fluctuations [1]. We wish to do the same type of comparisons in order to understand the effects of NBI on the fluctuations and thus the link between H-mode and turbulence. On the other hand, the application of an RF field, using either the ion cyclotron resonance (ICRH) or lower hybrid (LH) heating has shown strong effects on edge turbulence fluctuations [2]. We thus aim at investigating the effects of ECRH on TJ-II in order to complement our present understanding of the interaction between turbulence and RF fields. We hope to have 40 discharges with the first 100 ms as a start-up phase with ECRH. Then, we could either turn off the heating source or apply additional heating for the last 100 ms. The ECRH would be tuned off-axis and used near the maximum output. We will increase the NBI power gradually from one shot to another. The probes are expected to reciprocate once during the discharge. The two reciprocating probes would be better if they are magnetically connected in order to assess the effects on the parallel wavenumber especially when applying the ECRH. The electrical connections of the tips should allow the measurement of the poloidal electric field as well as the density fluctuations on one probe head. The other should allow the density fluctuations as well as the average plasma properties. The view of the fast imaging camera should be tangential if possible. We aim at writing one publication that summarizes the effects of NBI and ECRH on edge turbulence. The effects of ECRH on the fluctuations, quantified using the power spectrum and cross-correlation among the tips, would be presented. On the other hand, the link between the edge gradients and turbulence intensity and spatio-temperal properties will be discussed when applying NBI.

International or National funding project or entity

IAEA Joint Experiment, IAEA Agreement No. 22766/R0 concerning Research Project: “Fusion Physics and Technology Studies at the TJ-II Stellarator”, part of the IAEA Coordinated Research Project 'F13019' entitled ‘Network of Small and Medium Size Magnetic Confinement Fusion Devices for Fusion Research’

Description of required resources

Required resources:

  • Number of plasma discharges or days of operation: 1 to 2 days
  • Essential diagnostic systems: Two reciprocating Langmuir probe, fast imaging camera, He-Beam, microwave interferometer.
  • Type of plasmas (heating configuration): ECRH and NBI
  • Specific requirements on wall conditioning if any:
  • External users: need a local computer account for data access: yes
  • Any external equipment to be integrated? Provide description and integration needs:

Preferred dates and degree of flexibility

Preferred dates: (31-03-2020 to 02-04-2020)

References

  1. Antar et al PPCF 2008
  2. Antar et al PRL 2010, NF 2012 & 2013

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