Computational studies of current driven instabilites in a tokamak plasma

The system of nonlinear coupled equations in magnetohydrodynamics (MHD) is an extremely challenging area of research, due in part to their non-self-adjoint nature. This necessity has led to the development of numerical techniques for the accurate solution of these equations, particularly applied to the laboratory plasma devices such as tokamaks. Tokamak is one of the most successful candidates for the development of a fusion reactor. This work focuses on simulation of current driven instabilities occurring in tokamaks, particularly the tearing and kink modes, whose nonlinear evolution is not yet well understood and has a significant role in the operation and eventual success of tokamaks as reactors. These simulations are carried out using the CUTIE code [1] implementing novel computational techniques. Among these chiefly we have a modified TDMA method which improves the accuracy of our nonlinear calculations, nonlinearization method. We also describe the resolvent method, which is an eigenvalue method to quickly determine linear growth rates and frequencies, which serve as a check on the time evolution results. The simulation results are compared with experimental observations in ADITYA-U tokamak [2, 3, 4] for a better understanding of the tearing-mode behavior.

 

References:

[1] Visco-resistive MHD study of internal kink (m = 1) modes, J. Mendonca et al, Physics of Plasmas 25, 022504 (2018)

[1] Overview of recent experimental results from the Aditya tokamak, R. Tanna et al. October 2017, Nuclear Fusion 57(10):102008 

[2] Effect of periodic gas-puffs on drift-tearing modes in ADITYA/ADITYA-U tokamak discharges, Nuclear Fusion, Volume 60, Number 3, 036012

[4] A novel approach for mitigating disruptions using biased electrode in Aditya tokamak. Nucl. Fusion 54 (2014) 083023