Experimental study on edge E×B flow generated by fishbone burst on HL-2A tokamak

Previous studies have demonstrated that fishbone dynamics are dominated by wave-particle nonlinear interactions ^[1]. The secular outward motion of resonant energetic particles modifies frequency chirping through phase locking and mode saturation by maximizing wave-particle power exchange ^[2]. Recently, simulation works predict that the perturbed radial electric field associated with self-generated zonal flows could generate an E × B frequency ω_E×B which modifies the precessional resonance condition to ω=ω_d+ω_E×B^[3].

In our experiments, synchronizing fishbone burst, edge E×B flow increment and turbulence reduction are observed on HL-2A tokamak. We found that edge E×B flows generated by fishbone burst could change the mode saturation and frequency chirping through modification of wave-particle interaction condition. In addition, enhanced E×B flow could suppress turbulence and improve confinement.

[1] White, R. B., et al., 1983, Phys. Fluids 26, 2958.

[2] Fu, G. Y., et al., 2006, Phys. Plasmas 13, 052517

[3] G. Brochard, et al., 2024, Phys. Rev. Lett. 132, 075101