Simulating electromagnetic instabilities in tokamaks with gyrokinetic particle-in-cell code GTS

Recently, the numerical scheme presented in Refs.[1] enabled explicit gyrokinetic simulations of low-frequency electromagnetic instabilities in tokamaks at experimentally relevant values of plasma beta. This scheme resolved the long-standing "cancellation problem" that previously hindered gyrokinetic particle-in-cell code simulations of magnetohydrodynamic phenomena with inherently small parallel electric fields. Moreover, the scheme did not employ approximations that eliminate critical tearing-type instabilities. Here, we report on the implementation of this numerical scheme in the global gyrokinetic particle-in-cell code GTS. This implementation allows for a more complete and accurate picture of interaction

between small scale turbulence and MHD modes in tokamaks. Additionally, we present a comprehensive set of verification simulations of numerous electromagnetic instabilities relevant to present-day tokamaks. These simulations encompass the kinetic ballooning mode (KBM), the internal kink mode, the tearing mode, the micro-tearing mode (MTM) and toroidal alfven eigenmode (TAE) destabilized by energetic ions, which are all instrumental in understanding tokamak physics.

We will also showcase the preliminary nonlinear simulations of kinetic ballooning instabilities and (2,1) island formation due to tearing mode instability.

[1] A. Mishchenko, M. Cole, R. Kleiber, A. Konies, Phys. Plasmas 21 (2014) 052113.