Turbulent quenching of the drift-dissipative mode in a Q machine: theory and experiment

Current-generated broadband turbulence can appear to individual particles as a diffusive damping, leading to saturation of low-frequency modes in steady-state experiments. Mode saturation occurs when the linear growth γ = k⊥2D⊥, the diffusive damping. As long as mode frequency ω > k⊥2D⊥, the mode is well defined. When k⊥2D⊥ > ω, the mode loses meaning and should disappear. The turbulent damping k⊥2D⊥ is interpreted as an upper bound on the linewidth of the wave. As current increases, frequency falls and linewidth increases. The mode is quenched when damping exceeds the mode frequency. Agreement with experiment is good.