TJ-II:Role of isotope effect on biasing induced transitions in the TJ-II stellarator

Experimental campaign

2017 Spring

Proposal title

Role of isotope effect on biasing induced transitions in the TJ-II stellarator

Name and affiliation of proponent

S. Ohshima, Institute of Advanced Energy, Kyoto University, Kyoto, Japan

Details of contact person at LNF (if applicable)

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

Motivation Experimental studies have shown a reduction of the L-H power threshold by about 50% when using Deuterium instead of Hydrogen in tokamaks [1]. The influence of isotope mass on spontaneous L-H transition has been recently investigated in the TJ-II stellarator, concluding that Zonal Flows are instrumental both in H and D dominated plasmas to trigger the L-H transition [2].

Goals and planning We propose to investigate the influence of isotope mass (H vs D) on TJ-II electrode biasing induced transitions with to goals: 1. Study the influence of ion mass to reach biasing improved confinement regimes 2. Study the influence of magnetic configuration (ripple / iota) on biasing induced transitions

Experimental set-up Target plasma: ECRH and NBI plasmas Configuration: comparative studies in standard configuration (e.g. 100_42) and configuration with reduced volume (e.g. 100_30). Electrode position:  ~0.8 / Biasing ramp up/down up to 350 V Key diagnostics:
Dual Langmuir probe system (density, potential and LRC), HIBP (space potential, Er profiles fluctuation), Thomson scattering (Te, ne profiles), Doppler reflectometer (poloidal flow velocity, Er, fluctuations), ECE (Te profile), spectroscopy (H)

If applicable, 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:
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• 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

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References

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