TJ-II:L-H Transition and Isotope Effect in low magnetic ripple configurations

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Experimental campaign

2017 Spring

Proposal title

L-H Transition and Isotope Effect in low magnetic ripple configurations

Name and affiliation of proponent

T. Estrada, U. Losada, C. Hidalgo and the TJ-II team Laboratorio Nacional de Fusión CIEMAT


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

Experiments using deuterium as working gas have been carried out during the last experimental campaigns to study the isotope effect strength in TJ-II plasmas. The dependence of zonal flows on the ion mass was studied in low density ECH plasmas and no pronounced differences were found when comparing D and H plasmas [1]. More recently, higher density NBI heated plasmas have been studied and very similar values of zonal flow intensity in H and D have been also found at the L-H transition [2]. In these experiments, no signatures of isotope mass dependence were found at the L-H transition, neither in the radial electric field profile evolution nor in the turbulence reduction. In all cases experiments were performed in the standard magnetic configuration In order to investigate the impact of the magnetic configuration on the isotope effect we propose to perform similar experiments in a magnetic configuration with lower magnetic ripple, that is, with lower plasma volume.

[1] C. Hidalgo et al., Isotope effect on zonal flows: experiments in the TEXTOR tokamak and TJ‐II stellarator. 19th International Stellarator Heliotron Workshop, Padova, Italy, 2013.

[2] U. Losada et al., L-H Transition and Isotope Effect in TJ-II. 16th CWGM, Madrid, Spain, 2017.

If applicable, International or National funding project or entity

National funding project: ENE2013-48109-P

Description of required resources

Required resources:

  • Number of plasma discharges or days of operation: To prepare the experiment we need to search for L-H transitions in low volume plasmas. We propose to explore configuration between 100_26 and 100_30 to keep the iota profile in between the low rational surfaces 4/3 and 3/2. Once the proper conditions are found, we require two consecutive operation days, the first one with D and the second one with H.
  • Essential diagnostic systems: Doppler reflectometer, Langmuir probes, microwave interferometer, Thomson scattering, visible spectrometer, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry.
  • Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH
  • Specific requirements on wall conditioning if any: Fresh Li is required for a good density control using external puffing
  • 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: before 20-05-2017

References



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