Time-dependent 2D modeling of the X-I ECH and ECCD for solenoid-free start-up of a compact pilot plant*

The elimination of OH solenoid maybe the most impactful design driver for an economical compact fusion tokamak reactor system. To address this challenge, an efficient solenoid-free start-up and ramp-up scenario utilizing the X-mode at w = Ω_e (X-I) was proposed. The high ECCD efficiency is due to the strong wave-particle interactions at the Doppler broadened w = Ω_e resonance, together with the accessibility constrained absorption on uni-directional passing electrons. Using a compact pilot plant design, STAR, we investigate the feasibility of non-inductive current ramp-up from a zero current to a desired current level with available ECH power. The plasma current profile is controlled by controlling the ECH power deposition profile in real time. Effects of impurity radiation is added to the start-up RT-4 code to account for the intrinsic as well as injected impurities ion species. The impurities can cause the impurity radiative loss as well as the ECCD efficiency reduction through the Z-effective term.