@Article{ElfimovGalvGore:2019:GeMoDr,
author = "Elfimov, Artour G. and Galv{\~a}o, Ricardo Magnus Os{\'o}rio and
Gorelenkov, N. N.",
affiliation = "{Universidade de S{\~a}o Paulo (USP)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and {Princeton University}",
title = "Geodesic modes driven by untrapped resonances of NB energetic ions
in tokamaks",
journal = "Physics of Plasmas",
year = "2019",
volume = "26",
number = "10",
pages = "e102508",
month = "Oct.",
abstract = "Geodesic modes are typically excited by a minor concentration of
energetic ions, but unstable mode frequencies are substantially
different from Geodesic Acoustic Modes (GAMs) and are named EGAM
(Energetic particle GAM). The EGAM instability driven by Neutral
Beam Injection (NBI) has been observed in DIII-D tokamak
experiments. The problem of the geodesic mode instability is
analytically studied using a full drift kinetic equation. To
analyze the instability condition, an ionization NBI location is
assumed to be on the high field side of tokamaks. A minority NBI
ion distribution is modeled by an energetic ion tail in the
untrapped-passing region that remains between a magnetic axis and
the trapped NBI boundary. The EGAM instability condition is
defined by the parallel NBI ion velocity vjj ð1:2 1:5ÞxR0q0 that
has to be above the effective EGAM phase velocity. In this case,
the EGAM frequency is 50% below the standard stable GAM frequency,
which is reduced by a small concentration of energetic NBI ions.
Qualitative comparison of the developed geodesic mode theory with
NBI heating experiments in the midregion of the tokamak plasma is
discussed.",
doi = "10.1063/1.5110175",
url = "http://dx.doi.org/10.1063/1.5110175",
issn = "1070-664X",
language = "en",
targetfile = "elfimov_geodesic.pdf",
urlaccessdate = "05 jun. 2024"
}