Numerical Studies and Simulation of the Lower Hybrid Waves Current Drive by using Fokker - Planck Equation in NSST and HT-7 Tokamaks

Recent experiments on the spherical tokamak have discovered the conditions to create a powerful plasma and ensure easy shaping and amplification of stability, high bootstrap current and confinement energy. The spherical tours (ST) fusion energy development path is complementary to the tokamak burning plasma experiment such as NSTX and higher toroidal beta regimes and improves the design of a power plant. To support the ST development path, one option of a Next Step Spherical Torus (NSST) device has been examined. NSST is a performance extension stage ST with a plasma current of 5-10 MA, R=1.5m, Bt<2.7T with flexible physics. The baseline heating and current device system for NSST is the 30MW NBI system and a 10 MW of ion cyclotron range of frequency (ICRF) and high harmonic fast wave (HHFW) system. In this work, we investigated lower hybrid wave interaction in the NSST reactor and found an optimal lower hybrid wave power and frequency for it. Finally, we compared the lower optimal hybrid waves and NSST spherical tokamak with HT-7 tokamak. Our results indicated that the use of lower hybrid waves in improved spherical tokamak NSST, as compared to the HT-7, was much better and more efficient.