19 research outputs found
Gyrokinetic modelling of anisotropic energetic particle driven instabilities in tokamak plasmas
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
Global electromagnetic gyrokinetic simulations of Energetic Particle driven instabilities in ITER
Nonlinear interaction of Alfv\'enic instabilities and turbulence via the modification of the equilibrium profiles
Nonlinear simulations of Alfv\'en modes (AM) driven by energetic particles
(EP) in the presence of turbulence are performed with the gyrokinetic
particle-in-cell code ORB5. The AMs carry a heat flux, and consequently they
nonlinearly modify the plasma temperature profiles. The isolated effect of this
modification on the dynamics of turbulence is studied, by means of
electrostatic simulations. We find that turbulence is reduced when the profiles
relaxed by the AM are used, with respect to the simulation where the
unperturbed profiles are used. This is an example of indirect interaction of
EPs and turbulence. First, an analytic magnetic equilibrium with circular
concentric flux surfaces is considered as a simplified example for this study.
Then, an application to an experimentally relevant case of ASDEX Upgrade is
discussed
Numerical tools for burning plasmas
The software stack under development within a European coordinated effort on tools for burning plasma modelling is presented. The project is organised as a Task (TSVV Task 10) under the new E-TASC initiative (Litaudon et al 2022 Plasma Phys. Control. Fusion 64 034005). This is a continued effort within the EUROfusion inheriting from the earlier European coordination projects as well as research projects based at various European laboratories. The ongoing work of the TSVV Tasks is supported by the Advanced Computing Hubs. Major projects requiring the high performance computing (HPC) resources are global gyrokinetic codes and global hybrid particle-magnetohydrodynamics (MHD) codes. Also applications using the integrated modelling tools, such as the Energetic-Particle Workflow, based on the ITER Integrated Modelling & Analysis Suite (IMAS), or the code package for modelling radio-frequency heating and fast-ion generation may require intensive computation and a substantial memory footprint. The continual development of these codes both on the physics side and on the HPC side allows us to tackle frontier problems, such as the interaction of turbulence with MHD-type modes in the presence of fast particles. One of the important mandated outcomes of the E-TASC project is the IMAS-enabling of EUROfusion codes and release of the software stack to the EUROfusion community
Gyrokinetic modelling of anisotropic energeticparticle driven instabilities in tokamak plasmas
Effects of distribution functions in global gyrokinetic simulations of energetic particle driven Alfvénic and EGAM instabilities in ITER and ASDEX Upgrade
Anisotropic analytical and numerical distribution functions in the global gyrokinetic particle-in-cell code ORB5
Gyrokinetic modelling of anisotropic energeticparticle driven instabilities in tokamak plasmas
Gyrokinetic modeling of anisotropic energetic particle driven instabilities in tokamak plasmas
Energetic particles produced by neutral beams are observed to excite
energetic-particle-driven geodesic acoustic modes (EGAMs) in tokamaks. We study
the effects of anisotropy of distribution function of the energetic particles
on the excitation of such instabilities with ORB5, a gyrokinetic
particle-in-cell code. Numerical results are shown for linear electrostatic
simulations with ORB5. The growth rate is found to be sensitively dependent on
the phase-space shape of the distribution function. The behavior of the
instability is qualitatively compared to the theoretical analysis of dispersion
relations. Realistic neutral beam energetic particle anisotropic distributions
are obtained from the heating solver RABBIT and are introduced into ORB5 as
input distribution function. Results show a dependence of the growth rate on
the injection angle. A qualitative comparison to experimental measurements is
presented and few disagreements between them are found, being the growth rate
in the simulations much lower than that from experiments. An explanation for
the difference is advanced