View source for TJ-II: Determination of the spatial periodicity of NBI-driven Alfvén Eigenmodes and study of its magnetic configuration dependence

== Experimental campaign ==
Spring 2022

== Proposal title ==
Determination of the spatial periodicity of NBI-driven Alfvén Eigenmodes and study of its magnetic configuration dependence.

== Name and affiliation of proponent ==
[https://orcid.org/0000-0002-2250-9209 Álvaro Cappa], CIEMAT.
[https://orcid.org/0000-0000-0000-0000 Pedro Pons], CIEMAT.
[https://orcid.org/0000-0003-2101-0112 Macarena Liniers], CIEMAT.
[https://orcid.org/0000-0002-2250-9209 Enrique Ascasíbar], CIEMAT.

== Details of contact person at LNF ==
[https://orcid.org/0000-0002-2250-9209 Enrique Ascasíbar], CIEMAT.

== Description of the activity ==


MHD activity produced by Alfvén Eigenmodes (AEs) is routinely observed in NBI-heated TJ-II plasmas <ref>A. Cappa et al, Nuclear Fusion, 61(6):066019 (2021), and references therein</ref>. The results provided by recently installed sets of helical magnetic coils complement the previous experimental data and, together with advanced analysis tools like the 3D Lomb periodogram <ref>S. Zegenhagen, et al.,  Plasma Physics and Controlled Fusion, 48(9):1333–1346 (2006)</ref> allows the determination of the AEs spatial periodicity with an accuracy non reachable so far.

With this goal in mind we propose to study the alfvénic activity produced by both co and counter NBI injectors separately, as well as the one produced by simultaneous, balanced heating with both injectors (compensated plasma current). We plan to perform this study in at least two magnetic configurations, 100_44_64 (edge_iota 1.65) and 100_60_68 (1.77), looking for the expected influence of the configuration on the shear Alfvén spectrum.

Since we will be looking for reasonably stationary plasma density conditions to facilitate the mode analysis, we do not discard the use of moderate ECH heating during the NBI plasma phase.

== International or National funding project or entity ==


International: EUROfusion Consortium under grant agreements 633053 (FP8) and 101052200 (FP9).

National: Spanish Ministry of Science and Innovation under grants FIS2017-88892-P and FIS2017-85252-R

== Description of required resources ==
Required resources:
* Two days of good NBI plasma operation (35 discharges each) with good plasma density control (this request usually means that the operation days mus be allocated close after the boron/lihium conditioning of the vacuum vessel.
* 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 ==
Preferred dates: (format dd-mm-yyyy)

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== References ==
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