Speaker
Description
We report an analytical model for nonlinear collisionless electron cyclotron (EC) heating, accounting for electrons with non-zero initial perpendicular energy and high pitch angle under the 2nd harmonic, X-mode, perpendicular injection conditions with the help of the adiabatic Hamiltonian formulation [1]. During the tokamak pre-ionization stage, such electrons are expected to be present due to their low collisionality. However, the direct numerical integration of equations of motion for every resonant electron, especially at higher pitch angles [2], is too computationally expensive to implement it in breakdown transport simulations [3] and also complicated to apply for the 0D model such as burn-through modelling [4]. Therefore, analytic modelling is evidently necessary for designing the EC-injected startup scenarios in a tokamak. The proposed model provides an electron final energy, exhibiting good agreement with numerical integration results of equations of motion (see Figure 1 below) at a significantly reduced computational cost. We also report on total power absorption, assuming half transition probability for the Maxwellian distribution, and compare the results with numerical counterpart. This work is envisaged to contribute to sophisticated predictive modelling of EC pre-ionization and minimum required power for a successful plasma startup in ITER and beyond.
