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SUMMARY:Local gyro-Landau fluid simulations of toroidal drift wave modes a
nd drift-resistive-inertial ballooning modes in tokamak plasmas
DTSTART;VALUE=DATE-TIME:20210514T101000Z
DTEND;VALUE=DATE-TIME:20210514T103000Z
DTSTAMP;VALUE=DATE-TIME:20210417T013534Z
UID:indico-contribution-17622@conferences.iaea.org
DESCRIPTION:Speakers: Jianqiang Xu (Southwestern Institure of Physics)\nTr
ansport in magnetically confined devices is one of the key subjects in the
area of fusion relevant plasma research. Both theoretical and experimenta
l investigations have shown that the plasma confinement is largely control
led by drift wave fluctuations and associated anomalous transport across t
he magnetic field lines\, among whom the toroidal electrostatic ion temper
ature gradient mode (ITG) or electromagnetic kinetic ballooning mode (KBM)
\, trapped electron mode (TEM) and electron temperature gradient mode (ETG
) are of great importance [1]. Recent simulations have attracted a great i
nterest in understanding the type of turbulence in Ohmic and L-mode edge p
lasmas. One possible candidate that can describe the transport level at th
e edge of L-modes is the resistive ballooning modes (RBMs) [2]\, or drift-
resistive-inertial ballooning modes (DRIBMs) in which two fluid drift effe
cts and electron inertia are included [3]. Although various approaches suc
h as gyrokinetic and fluid models have been used to investigate the DRIBMs
\, the calculations of the modes have been treated as a separate fluid mod
ule of the simulation codes. Thus\, it is imperative for the construction
of an integrated transport model that is able to incorporate finite ion gy
ro radius effects at arbitrary order\, in which the widely applied electro
magnetic gyrofluid models [4]\, are proven to be a useful tool in understa
nding of plasma turbulence and the associated transport.\nFrom this prospe
ctive\, a local gyro-Landau fluid model is developed for the description o
f DRIBMs and toroidal drift wave modes in the collisional tokamak plasmas
based on the two-fluid reduced Braginskii equations in a generalized ŝ-$\
\alpha$ geometry. The six-moment model for both ion and electron incorpora
tes DRIBM\, ITG\, KBM and ETG\, as well as kinetic effects including finit
e Larmor radius effect (FLR) and Landau damping. The eigenvalues are obtai
ned by solving the linearized set of the model equations through standard
numerical algorithm. Besides\, particle transport driven by plasma instabi
lities at a given wavenumber k$\\theta$$\\rho$s can be estimated by ExB dr
ift motion in the radial direction through the quasi-linear theory with gr
owth rate and eigenvectors and as \, where the superscripts *r* and
*i* donates the real and imaginary parts of the perturbations\, respectiv
ely. The detailed beta dependence of the linear stabilities of ITG\, KBM a
nd ETG has been achieved under the Cyclone base case parameters. It is cle
arly shown that for small values of $\\beta$e=0 and 0.1%\, the dominating
instabilities are the mescal-scale ITGs and short-scale ETGs\, while for l
arge values of $\\beta$e=0.7% and 0.8%\, the transport is controlled by KB
Ms and ETGs with ITGs being fully suppressed. The plasma beta has little i
nfluence on the growth rate spectrum of ETG. It is also shown that the max
imum growth rates of ITG and ETG are comparable under low $\\beta$e cases\
, however\, the maximum eigenvalues of KBMs are substantially larger than
that of ETGs\, suggesting that the core plasma is dominated by low *k* KBM
turbulence\, as shown in Fig. 1(a). All of these modes will lead to the o
utward transport. The contribution of ETGs are almost unaffected by βe\,
implying that the ETGs can persist and may play an important role in the h
igh performance discharges\, particularly in the future fusion reactors\,
as shown in Fig. 1(b). \n![(a) growth rate and (b) dimensionless particle
flux as a function of k$\\theta$$\\rho$s for Cyclone base case parameters.
][1]\nHowever\, simulation results using JET-ILW edge-like parameters have
indicated that the transport process at the edge is mixed by intermediate
-scale (0.15) ETG turbulence\, which can be discovered in Fig. 2(a). Compa
red to the outward flux induced by ITG in the core plasma\, the ITG and DR
IBM produce the inward particle transport under L mode edge plasma conditi
ons with the contribution of the latter much larger than the former. The E
TG will induce the outward transport in the wavenumber region k$\\theta$$\
\rho$s>5. The combination of these effects has strongly suggested that tur
bulent transport is predominated by DRIBMs in the collisional plasma edge\
, as shown in Fig. 2(b). The above findings are clearly beneficial for the
understanding of the dominating instabilities and transport processes for
various plasma conditions and different regions.\n![(a) growth rate and (
b) dimensionless particle flux as a function of k$\\theta$$\\rho$s for JET
-ILW edge parameters.][2]\nAcknowledgment\nThis work was partly supported
by National Key R&D Program of China under Grant No. 2017YFE0301201 and Na
tional Natural Science Foundation (NSFC) under Grant Nos. 11775067\, 11775
069\, 11875019 and 11805058.\nReferences\n[1] Horton W. 1999 Rev. Mod. Phy
s. 71 735\n[2] Bateman G. et al 1978 Phys. Rev. Lett. 41 1804\n[3] Rafiq T
. et al 2010 Phys. Plasmas 17 082511\n[4] Scott B. D. 2005 Phys. Plasmas 1
2 102307\n\n\n [1]: https://i.loli.net/2020/03/13/MIxztAchYaRXf53.jpg\n
[2]: https://i.loli.net/2020/03/13/8w1y9gnW6duMoDl.jpg\n\nhttps://conferen
ces.iaea.org/event/214/contributions/17622/
LOCATION:Virtual Event
URL:https://conferences.iaea.org/event/214/contributions/17622/
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