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TJ-II: Determination of the spatial periodicity of NBI-driven Alfvén Eigenmodes and study of its magnetic configuration dependence: Difference between revisions
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TJ-II: Determination of the spatial periodicity of NBI-driven Alfvén Eigenmodes and study of its magnetic configuration dependence (view source)
Revision as of 10:45, 26 January 2022
, 26 January 2022→Description of required resources
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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. | 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. | 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. It time allows we do not discard the possibility of scanning the injector parameters (energy, beam current) to study their influence on the observed AEs. | ||
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. | 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. | ||
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Required resources: | Required resources: | ||
* Two days of good NBI plasma operation (aprox. 35 discharges each) with reasonably good plasma density control. | * Two days of good NBI plasma operation (aprox. 35 discharges each) with reasonably good plasma density control. | ||
* Essential diagnostic systems: Mirnov coils (helical and poloidal arrays) and CNPA measurements are mandatory. Besides the common shot to shot diagnostics (ECE, Thomson, Interferometry, Radiation), all systems providing edge plasma profiles are needed. If possible, Doppler Reflectometer, HIBP. MSE would also be desirable to evaluate configuration | * Essential diagnostic systems: Mirnov coils (helical and poloidal arrays) and CNPA measurements are mandatory. Besides the common shot to shot diagnostics (ECE, Thomson, Interferometry, Radiation), all systems providing edge plasma profiles are needed. If possible, Doppler Reflectometer, HIBP. MSE would also be desirable to evaluate configuration changes induced by non-totally balanced currents. FILD is also desirable to monitor fast ion losses and relate the level of losses to the Alfven activity. | ||
* Type of plasmas (heating configuration): NBI (both injectors) and ECH. | * Type of plasmas (heating configuration): NBI (both injectors) and ECH. | ||
* Specific requirements on wall conditioning if any: Good plasma density control usually means that the operation days must be allocated close after the boron/lihium conditioning of the vacuum vessel. | * Specific requirements on wall conditioning if any: Good plasma density control usually means that the operation days must be allocated close after the boron/lihium conditioning of the vacuum vessel. | ||