Drift wave turbulence and transport analysis of hot ion L-mode plasma with fishbone instability on HL-3 tokamak

Abstract

An integrated analysis of the HL-3 hot-ion L-mode (shot \#11972, $T_i/T_e\approx 3$, $T_i(0)\approx 9.8$\,keV) establishes the cross-scale coupling by which a single $m=1,n=1$ fishbone mode governs both toroidal rotation and ion-scale drift-wave turbulence. Multi-diagnostic measurements, OMFIT integrated modeling, and TGLF quasilinear simulations show that a steep fast-ion pressure gradient under 2.5\,MW co-injected NBI excites the fishbone. Its outward redistribution of resonant fast ions decouples the NBI torque, and the sawtooth crash it triggers collapses the rotation from above $100$ to $60$\,krad/s. The same fast ions that drive the fishbone also stabilize ion-scale ITG/TEM turbulence, so their redistribution removes the ITG stabilization carried by the high temperature ratio, fast-ion dilution, and $E\times B$ shear, and erodes the internal transport barrier. Two-dimensional flux and one-dimensional eigenvalue scans confirm that the high temperature ratio and the fast-ion population together suppress particle, energy, and momentum transport. These findings close one cross-scale coupling loop spanning MHD, fast-ion transport and microturbulence, in which one mode drives both momentum balance and turbulence stability. The results offer a predictive framework for fast-ion confinement and rotation sustainment in the upcoming deuterium tritium phase, and for burning plasmas where alpha particles likewise drive MHD activity and damp turbulence.

arXiv comment19pages and 17 figs