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The work reported in this paper addresses two aspects. In the first part, numerical simulations are conducted to examine the impact of magnetic equilibrium shaping (elongation and triangularity), on both conventional Ion Temperature Gradient (ITG) modes and Short Wavelength ITG modes. This analysis is performed considering the experimental profiles and parameters of the ADITYA-U tokamak, employing the nonlinear global gyrokinetic Particle-in-Cell code ORB5. The linear and nonlinear collisionless electrostatic simulation of these modes are carried out with kinetic ions and adiabatic electrons. From the linear results, it has been observed that the magnetic equilibrium shaping slighty reduced the growth rates and widened the spectrum, and the maxima of growth rate curve is shifted to higher toroidal wave number. We find that the heat flux is reduced by a significant ≃ 35 % for the true circular magnetohydrodynamic magnetic equilibrium as compared to ad hoc concentric circular equilibrium reported in Singh et al (2023 Nucl. Fusion 63 086029). A further ≃ 10 % reduction in the heat flux is seen with magnetic equilibrium shaping. In the second part, linear collisionless electrostatic simulation studies of ITG coupled with fully kinetic electrons (both trapped and passing electrons are treated kinetically) using a drift-kinetic ordering is performed. It can be seen from the linear results that, in presence of kinetic electrons, the growth rate and real frequency of the ITG mode are increased significantly for ADITYA-U parameters and a mode propagating in the electron diamagnetic direction is identified at high toroidal wavenumbers. [ABSTRACT FROM AUTHOR]

Electromagnetic turbulence is addressed in tokamak and stellarator plasmas with the global gyrokinetic particle-in-cell codes ORB5 (E Lanti et al, Comp. Phys. Comm., 251 , 107072 (2020)) and EUTERPE (V Kornilov et al, Phys. Plasmas, 11 , 3196 (2004)). The large-aspect-ratio tokamak, down-scaled ITER, and Wendelstein 7-X geometries are considered. The main goal is to increase the plasma beta, the machine size, the ion-to-electron mass ratio, as well as to include realistic-geometry features in such simulations. The associated numerical requirements and the computational cost for the cases on computer systems with massive GPU deployments are investigated. These are necessary steps to enable electromagnetic turbulence simulations in future reactor plasmas. [ABSTRACT FROM AUTHOR]

A detailed cross-verification between two global gyrokinetic codes, the core continuum code GENE and the edge particle-in-cell code XGC, for the linear and nonlinear simulations of ion-temperature-gradient modes is carried out. With the recent developments in the edge gyrokinetics, it may be feasible someday to describe the whole tokamak plasma on turbulence timescales using a coupled gyrokinetic simulation model. Before pursuing this, the core code (GENE) and the edge code (XGC) must be carefully benchmarked with each other. The present verification provides a solid basis for future code coupling research. Also included in the benchmarking is the global particle-in-cell code ORB5, to raise the confidence in the quality of the obtained results. An excellent agreement between all three codes is obtained. Furthermore, in order to facilitate a benchmark framework for other codes, we make a specific effort to provide all the relevant input parameters and precise details for each code. [ABSTRACT FROM AUTHOR]

A new version of GBS (Ricci et al. (2012) [27] ; Halpern et al. J. Comput. Phys. 315 (2016) 388-408; Paruta et al. (2018) [11]) is described. GBS is a three-dimensional, flux-driven, global, two-fluid turbulence code developed for the self-consistent simulation of plasma turbulence and kinetic neutral dynamics in the tokamak boundary. In the new version presented here, the simulation domain is extended to encompass the whole plasma volume, avoiding an artificial boundary with the core, hence retaining the core-edge-SOL interplay. A toroidal coordinate system is introduced to increase the code flexibility, allowing for the simulation of arbitrary magnetic configurations (e.g. single-null, double-null and snowflake configurations), which can also be the result of the equilibrium reconstruction of an experimental discharge. The implementation of a new iterative solver for the Poisson and Ampère equations is presented, leading to a remarkable speed-up of the code with respect to the use of direct solvers, therefore allowing for efficient electromagnetic simulations that avoid the use of the Boussinesq approximation. The self-consistent kinetic neutral model, initially developed for limited configurations, is ported to the magnetic configurations considered by the present version of GBS and carefully optimized. A new MPI parallelisation is implemented to evolve the plasma and neutral models in parallel, thus improving the code scalability. The numerical implementation of the plasma and neutral models is verified by means of the method of manufactured solutions. As an example of the simulation capabilities of the new version of GBS, a simulation of a TCV tokamak discharge is presented. • The GBS code is now able to simulate medium size tokamaks with realistic geometry and magnetic equilibrium. • The use of a non-field aligned grid combined with the MPI domain decomposition allow for a very efficient code scalability. • The plasma model is coupled to a kinetic neutral model improving the reliability of tokamak boundary turbulence simulations. • The use of iterative solvers for Poisson and Ampère laws significantly improve the code performance. [ABSTRACT FROM AUTHOR]