TJ-II:Dependence of NBI-driven Alfvén Eigenmodes on NBI energy and power

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Experimental campaign

2018 Spring

Proposal title

Dependence of NBI-driven Alfven Eigenmodes on energy and power of the neutral beams in a current compensated scenario

Name and affiliation of proponent

Á. Cappa, E. Ascasíbar, M. Liniers, F.Castejón

LNF-CIEMAT

Details of contact person at LNF (if applicable)

Enter contact person here or N/A

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

The primary goal of the proposal is to determine the influence of the NBI injectors parameters (voltage, current) on the observed Alfvén Eigenmodes (AEs) activity of the device, looking for voltage-current configurations at approximate constant power for which the AEs activity is lower. The behaviour of the NBI driven current is an essential element that must be taken into account since the AEs activity may show a dependence on iota through plasma current variations induced by the changes in voltage (at constant power) comparable to the effects that the voltage variations themselves may have on the wave-particle resonance condition. To decouple both effects, an attempt to compensate the NBI driven current, while scanning the parameters of the NBI, is proposed. Target plasma is created by off-axis ECRH (ensuring no ECCD is driven). In principle, no ECRH power is needed during the NBI phase as long as a smooth evolution of the plasma density is achieved. If this is not possible, ECRH may be used during the NBI phase in order to control the plasma density.

  • Target plasma using ECRH, then ECRH is switched off and only used if good density control is not achieved.
  • Three different values of NBI power shall be used, using the same power in both injectors and the same voltage-current pair.
  • For each power value, four values of voltage are tested simultaneously in each beam paying attention to keep a more less

constant plasma current which ideally should mainly come from the bootstrap contribution.

  • Two reproducible shots per voltage. Alternatively, the length of one of the beams may be 20-30 ms shorter than the

other one in order to isolate the mode excitation that corresponds to each beam and identify which beam drives which modes.

  • 24 shots in total. One day of operation.

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: 24 (1 day)
  • Essential diagnostic systems: Mirnov Coils (poloidal and new helicoidal array), rest of magnetic fluctuations diagnostics, all standard diagnostics (Thomson, ECE, Radiation, Interferometry), Doppler reflectometry, HIBP.
  • Type of plasmas (heating configuration): 100_44_64
  • Specific requirements on wall conditioning if any: Good density control
  • External users: need a local computer account for data access: No external users
  • Any external equipment to be integrated? No

Preferred dates and degree of flexibility

Preferred dates: (format dd-mm-yyyy)

From 23rd to 25th May A. Cappa will be not available.

References



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