Simulation of lower hybrid wave in fusion plasma using FullWave*

FAR-TECH, Inc. has been developing the FullWave code,  a hybrid-iterative full wave solver, to model rf waves in hot plasmas including the nonlocal hot plasma responses. The code uses configuration space to discretize wave equations and calculate the nonlocal hot plasma dielectric response.

 

To extend the capability to lower frequencies such as Lower-Hybrid and Helicon waves, an implicit time-stepping algorithm has been implemented. The hybrid iterative algorithm significantly increases spatial resolution of the RF fields but requires time steps to be comparable to Courant condition in explicit methods to fully resolve electron inertia.

 

 We have explored ways to speed up the FullWave simulation by implementing direct solver and local implicit scheme. Direct solver solves the full wave equations in the frequency domain by inverting the conductivity kernal tensor by utilizing SuperLU-Dist library. We have tested direct solver on 50M computation points for cold plasma model on NERSC.  The locally implicit method solves the Ampere’s law implicitly on each computation point while the Faraday’s law is solved explicitly. The convergence and calculation speed are improved by several times using this scheme than the implicit time-stepping scheme. We will present recent 1D and 2D FullWave simulations in cold model using DIII-D parameters.

 

In addition, hot conductivity kernel calculations in the range of LH will be presented.