Detection and investigation of chirping Alfvén eigenmodes with heavy ion beam probe in the TJ-II stellaratorстатья
Статья опубликована в высокорейтинговом журнале
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 11 апреля 2019 г.
Местоположение издательства:[Bristol, UK], England
Первая страница:2
Последняя страница:9
Аннотация:Alfvén eigenmodes were studied in the low magnetic shear flexible heliac TJ-II NBI-heated
plasmas by heavy ion beam probe (HIBP), which is capable to measure simultaneously the
oscillations of the plasma electric potential, density and poloidal magnetic field in the bulk
plasmas. The L-mode hydrogen plasma was investigated at various magnetic configurations
with rotational transform ι(a)/2π ~ 1.5–1.6. Co-, counter- and balanced beam injection
were explored. The present study was focused on the high-frequency chirping modes with
250 kHz < fAE < 350 kHz at the low-density ne = (0.5–0.7) × 1019 m−3 NBI-heated
plasmas without auxiliary ECRH. Here we report the observation of the various types of
chirping modes, differing by frequency, radial location, amplitude and shape of the frequency
dependence on time (burst pattern). Remarkably, the same mode may evolve, changing its
burst pattern in the same frequency range in the single discharge. The radial scan of the HIBP
sample volume indicates the radial evolution of the potential and density perturbation during
the single frequency burst of the chirping mode. The individual burst of the chirping-up mode
can propagate outward with volume-averaged radial velocity ≈70 m s−1. The frequency raise
during the burst is in line with Alfvén frequency dependence on density, which decreases over
the propagation area.
Keywords: Alfvén eigenmodes, chirping, TJ-II stellarator
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