Analysis of ECRH Pre-Ionization for Plasma Start-Up in JT-60SA

Plasma start-up assisted by electron cyclotron resonance heating (ECRH) pre-ionizationis theoretically studied for the superconducting tokamak JT-60SA by using a zero-dimensional (0-D) model. Because the toroidal electric field is limited to 0.5 Vm−1, we clarify the conditions for a robust plasma initiation. Five temporal equations are solved for a spatially-uniform plasma: the electron and neutral density equations, the electron and ion energy density equations, and the electric circuit equation. The numerical calculation results show that an absorbed ECRH power of 150 kW is required to start up the plasma, assuming an initial neutral density of 3.0×1018 m−3, and that reducing the oxygen and carbon impurity densities facilitates successful start-up. We discuss the dependence of the absorbed ECRH power on the neutral density and impurities. The simulation qualitatively reproduces experimental results from JT-60U.