Parametric Decay of Lower-Hybrid Waves in the ACT-1 Toroidal Device

Abstract

Nonresonant parametric decay of lower-hybrid waves, observed in a number of high-power tokamak rf-heating experiments, is positively identified as a decay into ion-cyclotron quasimodes. The decay-wave spectrum, wavelength, and amplitude profile are measured inside a toroidal plasma with pump frequency $f_0\sim 3.5f_{\mathrm{pi}}\sim 25f_{\mathrm{ci}}$.