Kinetic particle simulations in a global toroidal geometry

Abstract

The gyrokinetic toroidal code (GTC) has been upgraded for global simulations by coupling the core and scrapeoff layer (SOL) regions across the separatrix with field-aligned particle-grid interpolations. A fully kinetic particle pusher for high frequency waves (ion cyclotron frequency and beyond) and a guiding center pusher for low frequency waves have been implemented using cylindrical coordinates in a global toroidal geometry. The two integrators correctly capture the particle orbits and agree well with each other, conserving energy and canonical angular momentum. As a verification and application of this new capability, ion guiding center simulations have been carried out to study ion orbit losses at the edge of the DIII-D tokamak for single null magnetic separatrix discharges. The ion loss conditions are examined as a function of the pitch angle for cases without and with an electric field. The simulations show good agreement with past theoretical results and with experimentally observed feature in which high energy ions flow out along the ion drift orbits and then hit the divertor plates. A measure of the ion direct orbit loss fraction shows that the loss fraction increases with the ion energy for DIII-D in the initial velocity space. Finally, as a further verification of the capability of the new code, self-consistent simulations of zonal flows in the core region of the DIII-D tokamak were carried out.

Development and testing of an unstructured mesh method for whole plasma gyrokinetic simulations in realistic tokamak geometry

“…In order to simulate the edge physics, besides comprehensive physics models 12,13 , numerical schemes such as finite element methods for unstructured meshes in XGC 5, 14 , GTS 4 and GTC/GTC-X 15,16 and multiple patches of structured meshes in JOREK 11 have been developed in order to treat the open field line (OFL) region. While whole plasma simulations for neoclassical transport, ELMs and micro-turbulence have been reported and various numerical schemes have been developed for treating the OFL geometry 5, 10,11,15,17,18 , there is still space to understand the features of different schemes, such as the particle-in-Fourier method (cf. [19,20] and references therein), and thus to optimize the efficiency and the fidelity of the whole volume simulation.…”

A Note on Optimal Tokamak Control for Fusion Power Simulation

“…A similar analytical approach was also mentioned in the book [1]. Apart from the analytical studies, experimentally motivated papers on Tokamak and Stellarator that are very important for Modelling a Tokamak are well existed in the literature [13,14,15,16,17,18,19,20,21]. The existence of turbulence on the outer part of Tokamak plasma brings hindrance against achieving the steady stable plasma state, thereby attracting a significant number of researchers to address this issue in their relevant papers [21,17,14].…”

“…Apart from the analytical studies, experimentally motivated papers on Tokamak and Stellarator that are very important for Modelling a Tokamak are well existed in the literature [13,14,15,16,17,18,19,20,21]. The existence of turbulence on the outer part of Tokamak plasma brings hindrance against achieving the steady stable plasma state, thereby attracting a significant number of researchers to address this issue in their relevant papers [21,17,14]. As the Tokamak plasma is kept at an extremely high temperature, several uncertainty regarding intrinsic plasma properties such as its thermal conductivity, electrical conductivity starts to change in an unpredictable manner, thereby generating scope for analyzing such a phenomena borrowing the tools and techniques from uncertainty quantification and reinforcement learning as can be found in [22,23,24,25].…”