140 research outputs found
Corrigendum: Electromagnetic turbulence suppression by energetic particle driven modes (2019 Nucl. Fusion 59 124001), Nuclear Fusion 60, 089501 (2020)
In recent years, a strong reduction of plasma turbulence in the presence of
energetic particles has been reported in a number of magnetic confinement
experiments and corresponding gyrokinetic simulations. While highly relevant to
performance predictions for burning plasmas, an explanation for this primarily
nonlinear effect has remained elusive so far. A thorough analysis finds that
linearly marginally stable energetic particle driven modes are excited
nonlinearly, depleting the energy content of the turbulence and acting as an
additional catalyst for energy transfer to zonal modes (the dominant turbulence
saturation channel). Respective signatures are found in a number of simulations
for different JET and ASDEX Upgrade discharges with reduced transport levels
attributed to energetic ion effects
Gyrokinetic investigation of the nonlinear interaction of Alfvén instabilities and energetic-particle driven geodesic acoustic modes
Gyrokinetic modelling of anisotropic energetic particle driven instabilities in tokamak plasmas
Interaction of Alfvénic modes and turbulence via the nonlinear modification of the equilibrium profiles
ORB5: a global electromagnetic gyrokinetic code using the PIC approach in toroidal geometry
This paper presents the current state of the global gyrokinetic code ORB5 as
an update of the previous reference [Jolliet et al., Comp. Phys. Commun. 177
409 (2007)]. The ORB5 code solves the electromagnetic Vlasov-Maxwell system of
equations using a PIC scheme and also includes collisions and strong flows. The
code assumes multiple gyrokinetic ion species at all wavelengths for the
polarization density and drift-kinetic electrons. Variants of the physical
model can be selected for electrons such as assuming an adiabatic response or a
``hybrid'' model in which passing electrons are assumed adiabatic and trapped
electrons are drift-kinetic. A Fourier filter as well as various control
variates and noise reduction techniques enable simulations with good
signal-to-noise ratios at a limited numerical cost. They are completed with
different momentum and zonal flow-conserving heat sources allowing for
temperature-gradient and flux-driven simulations. The code, which runs on both
CPUs and GPUs, is well benchmarked against other similar codes and analytical
predictions, and shows good scalability up to thousands of nodes
Effect of temperature anisotropy on the dynamics of geodesic acoustic modes
In this work, we revisit the linear gyro-kinetic theory of geodesic acoustic
modes (GAMs) and derive a general dispersion relation for an arbitrary
equilibrium distribution function of ions. A bi-Maxwellian distribution of ions
is then used to study the effects of ion temperature anisotropy on GAM
frequency and growth rate. We find that ion temperature anisotropy yields
sensible modifications to both the GAM frequency and growth rate as both tend
to increase with anisotropy and these results are strongly affected by the
electron to ion temperature ratio
Growth-induced breaking and unbreaking of ergodicity in fully-connected spin systems
Two canonical models of statistical mechanics, the fully-connected voter and
Glauber-Ising models, are modified to incorporate growth via the addition or
replication of spins. The resulting behaviour is examined in a regime where the
timescale of expansion cannot be separated from that of the internal dynamics.
Depending on the model specification, growth radically alters the long-time
dynamical behaviour by breaking or unbreaking ergodicity.Comment: 10 pages, 3 figures, 1 tabl
A linear benchmark between HYMAGYC, MEGA and ORB5 codes using the NLED-AUG test case to study Alfvénic modes driven by energetic particles
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