Influence of Alfvén eigenmode on the distribution of alpha particles in CFEDR

Abstract

The confinement of fusion alpha particles is critical for burning plasma operation in the China Fusion Engineering Demo Reactor (CFEDR). For rapid parameter scans during CFEDR design, using self-consistent profiles from an integrated modeling workflow, we apply two reduced models using critical gradient model (CGM), TGLFEP to evaluate the critical density gradient and Alfvén eigenmode (AE) instability driven by fusion alpha particles in the CFEDR conventional H-mode scenario, and EPtran to evolve the transport of alpha particles born at 3.5 MeV. The critical gradient profile indicates that the classical slowing down gradient lies close to the AE excitation threshold at several core locations. TGLFEP analysis reveals AE is weakly unstable with high toroidal mode number , such as TAEs with n∼23-32, γ/ω<1% at r/a=0.4. However, EPtran indicates that the AE related diffusivity leads to only small additional changes in the core alpha particle profiles and fluxes relative to ITG/TEM background transport, within the local approximation and CGM assumption.