Damping and accumulation characteristics of flow driven by fishbone instability

The persistence of fishbone-driven flows across successive bursts is critical to their potential role in regulating turbulence and improving core confinement, yet the damping characteristics of such flows have not been experimentally characterized. Here we report the first direct measurement of the damping rate of fishbone-driven flows using Doppler reflectometry on the EAST tokamak. The experimentally obtained damping rate exceeds prior theoretical predictions, and this discrepancy can be reconciled by incorporating the effective charge number Zeff into the accalculation of the damping rate. Furthermore, we observe that flow accumulation occurs when the time interval between successive fishbone bursts is sufficiently short, and we estimate the critical inter-burst interval threshold for accumulation to be approximately 1 ms under the present discharge conditions. These results establish an essential experimental foundation for understanding the temporal persistence of fishbone-driven flows and their implications for transport barrier dynamics.