Numerical analysis of helium ash removal by using ICRH-driven ripple transport

Helium ash removal across the last closed flux surfaces in a deuterium-tritium fuelled tokamak plasma is studied using an orbit-following Monte Carlo simulation. Ripple transport of helium ash ions is induced by ion cyclotron resonance heating (ICRH) of short-lived He⁺ ions, which are produced by charge exchange of He²⁺ with incoming neutral species. It is found that the required ICRH power in an ITER grade tokamak plasma is 10-15 MW and the helium transport to the first wall is localized within an area given by 1.3 m in the toroidal direction and 0.7 m in the poloidal direction.