Time: Thursday, Oct. 28th, 4:00pm
Venue: Room 413, Buil. 11th, YuQuan Campus
Speaker: 仇志勇
Title: Nonlinear decay of reversed shear Alfvén eigenmodes and core-localized alpha-channeling
Abstract: The confinement of fusion alpha particles as well as transferring their power to fuel ions are crucial for sustained burning plasma operations in future reactors. In this work, a novel process for fuel ion heating in tokamak center is proposed and analyzed using gyrokinetic theory. The “alpha-channeling” is achieved via spontaneous decay of reversed shear Alfvén eigenmodes (RSAEs), resonantly excited by fusion alpha-particles”, into low frequency Alfvén modes (LFAMs), which then heat fuel ions via collisionless Landau damping. This novel mechanism, which is expected to be ubiquitous in high-confinement fusion plasmas, provides a complementary and competing route to core-ion heating with respect to the collisional heating, which is expected to be less efficient due to the low collisionalities in reactors. The conditions for this process to occur are analyzed, and the resulting power of ion heating is estimated.
This process, based on RSAE nonlinear decay, is expected to be important in the advanced reversed shear scenarios of future reactors, where RSAEs are expected to be preferentially excited by core-localized fusion alphas, and multiple RSAEs can be excited simultaneously due to much larger system size than the characteristic orbit widths of alpha particles.