Simulation of plasma turbulence in the periphery of diverted tokamak by using the GBS code

Abstract

We report on the implementation of diverted magnetic equilibria in GBS and on first simulations in this geometry. GBS is a simulation code used to evolve plasma turbulence in the tokamak periphery by solving the drift-reduced Braginskii's equations. The model equations are written in toroidal coordinates, abandoning flux coordinate systems that are not defined at the X-point. A fourth order finite difference scheme is used for the implementation of the spatial operators on poloidally and toroidally staggered grids. The GBS numerical implementation is verified through the method of manufactured solutions. The code convergence properties are tested on a relatively simple analytical X-point configuration. Finally, the diverted equilibrium from a TCV tokamak discharge is implemented in the new version of GBS. The analysis of the simulation results is focused on blob formation, radial transport, and plasma poloidal rotation mechanisms.

Blob velocity scaling in diverted tokamaks: A comparison between theory and simulation

“…The details of the derivation of the differential operators can be found in Ref. 33. Since the physical model in Eqs.…”

“…We note that a more complete version of the equations implemented in GBS for diverted magnetic configurations is presented in Ref. 33. The GBS version for a limited configuration additionally solves neutral dynamics and can be run without the Boussinesq approximation for the vorticity and with electromagnetic effects.…”

“…The simulation is carried out with the GBS code. GBS [31][32][33] is a 3D code that simulates the plasma turbulent dynamics in the tokamak periphery by evolving the two-fluid drift reduced Braginskii's equations. 34,35 In the past few years, GBS has helped investigating plasma dynamics in limited tokamaks, for example, by providing predictions of the SOL width.…”

“…34,35 In the past few years, GBS has helped investigating plasma dynamics in limited tokamaks, for example, by providing predictions of the SOL width. 36 Recently, GBS capabilities have been extended to the simulation of diverted scenarios, 33 by abandoning the use of flux coordinates, which present a singularity at the X-point.…”

A gyrokinetic model for the plasma periphery of tokamak devices

“…Over the last decades, successful and significant progress has allowed important advances in the simulation of the turbulent plasma dynamics in the periphery. Both fluid (Dudson et al 2009;Tamain et al 2009;Ricci et al 2012;Easy et al 2014;Ricci 2015;Halpern et al 2016;Paruta et al 2018) and first-principle based gyrokinetic simulations (Xu et al 2007;Cohen & Xu 2008;Ku et al 2009;Shi et al 2015;Hakim et al 2016;Pan et al 2016;Chang et al 2017;Pan et al 2018) have been used to achieve this goal.…”