Mode evolution of TAE due to alpha particles and synergy with ripple loss in CFETR

Abstract

The alpha particle should have good confinement when there are instabilities and toroidal field ripples in fusion devices. With the alpha particle slowing down distribution generated by TRANSP/NUBEAM, the Alfven eigenfunction calculated by NOVA/NOVA-K, and a quasilinear model in the ORBIT code, the study investigated the nonlinear evolution of Toroidal Alfven Eigenmodes (TAE) driven by alpha particles and the resulting transport, particularly focusing on the synergistic effects with ripple loss. The amplitude level of strong pulsations is about ${A_n} = 5.0 \times {10^{ - 4}}{R_0}$ , frequency chirping and particle transport in phase space are also observed. Enhancement of the saturation level does not occur because the two mode-particle resonant regions are well separated. No synergistic effect of TAE and toroidal field ripple perturbation on alpha particle loss was observed. This is because co-passing particles near the core dominated the mode particle resonance. Only trapped particle redistribution and flattening near the edge can have particle loss enhancement. The conclusions of saturation amplitude, particle transport, and synergy with ripple loss have no concerns for the present scenario of CFETR, but no synergy is not a general conclusion and should be investigated case by case. The methodology demonstrated in this work is general and can facilitate rapid iteration of engineering and physics for fusion reactor design.

Keywords

• tokamak
• alpha particle
• TAE
• nonlinear dynamics
• toroidal field ripple