TJ-II:Searching for AEs suppression scenarios using off-axis ECCD

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Experimental campaign

Spring 2022

Proposal title

Searching for AEs suppression scenarios using off-axis ECCD

Name and affiliation of proponent

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John Doe, University of Ivory Tower

Details of contact person at LNF

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Description of the activity

Enter description here [1], including motivation/objectives and experience of the proponent (typically one-two pages)

The goal of the proposal is to find ECRH launching configurations for which the amplitude of NBI-driven Alfvén Eigenmodes (AEs) is mitigated. Besides the interest that such scenarios have for the fast particles topic, studies of coupling between NBI-driven AEs and low frequency zonal flows may also benefit from them. Many scenarios making use of different "control" parameters have already been tested in past experimental sessions, showing always strong changes in AEs activity. Plasma density variations and changes of the rotational transform profile due to the many contributions to the total plasma current (NBCD, ECCD, Bootstrap current) are the parameters with the higher impact. However, although inducing modifications in the general spectrum of the excited modes, none of the investigated scenarios show a clear possibility to suppress AEs without inducing large changes in plasma parameters, being the most promising the one employing ECCD. In this particular case we intend to investigate the effect of off-axis ECCD at different plasma radius.

Background

The goal of the proposal is to find ECRH launching configurations for which the amplitude of NBI-driven Alfvén Eigenmodes (AEs) is mitigated. Besides the interest that such scenarios have for the fast particles topic, studies of coupling between NBI-driven AEs and low frequency zonal flows may also benefit from them. Many scenarios making use of different "control" parameters have already been tested in past experimental sessions, showing always strong changes in AEs activity. Plasma density variations and changes of the rotational transform profile due to the many contributions to the total plasma current (NBCD, ECCD, Bootstrap current) are the parameters with the higher impact. However, although inducing modifications in the general spectrum of the excited modes, none of the investigated scenarios show a clear possibility to suppress AEs without inducing large changes in plasma parameters, being the most promising the one employing ECCD. In this particular case we intend to investigate the effect of off-axis ECCD at different plasma radius.

Experimental plan

Figure 1. Heating scheme. ECH1 beam, used to induce current, is launched with two different power levels for gyrotron stability purposes

Until now, only ECCD on-axis has been investigated. We will now try to modify the rotational transform profile by inducing ECCD off-axis with different levels of power at different plasma radius. The heating power set-up shown in figure 1 will allow us to investigate the effect of ECCD using different combinations of ECH1 beam power and ECCD efficiency. With this set-up, launching ECH2 power with , only a small amount of ECCD current will be induced by the ECH1 beam during the ECRH phase while the larger amount of ECCD will be induced during the NBI phase by increasing the ECH1 beam power. For stability purposes ECH1 must be working at low power from the begginning of the shot until higher power is requested.

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:
  • Essential diagnostic systems:
  • 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

  1. A. Einstein, Journal of Exceptional Results (2017)

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