Alpha-Particle-Driven Toroidal Alfvén Eigenmodes in the Tokamak Fusion Test Reactor

Alpha-particle-driven toroidal Alfvén eigenmodes (TAEs) have been observed for the first time in deuterium-tritium (D-T) plasmas on the tokamak fusion test reactor (TFTR). These modes are observed 100–200 ms following the end of neutral beam injection in plasmas with reduced central magnetic shear and elevated central safety factor $[q\left(0\right)>1\mathrm{}]$. Mode activity is localized to the central region of the discharge $\left(r/a<\mathrm{}0.5\mathrm{}\right)$ with magnetic fluctuation level ${\tilde{B}}_{\perp }{/B}_{\parallel }\sim {10}^{-5\mathrm{}}$ and toroidal mode numbers in the range $n=2\mathrm{}–4$, consistent with theoretical calculations of α-TAE stability in TFTR.