Observation of Large-Amplitude, Narrow-Band Density Fluctuations in the Interior Region of an Ohmic Tokamak Plasma

Strong spatial asymmetries in the spectrum and magnitude of low-frequency ($\omega \ll {\omega }_{\mathrm{ci}}$) density fluctuations have recently been measured in the Texas experimental tokamak. Large-amplitude, narrow-band (as low as $\frac{\Delta \omega }{\omega }\simeq 0.1$) modes have been observed on the inside of the high-field torus in addition to the typical broad-band ($\frac{\Delta \omega }{\omega }\simeq 1$) microturbulence which is present throughout the plasma cross section. These narrow-band fluctuations are only detected at the plasma interior, being localized towards the midplane, and are not seen at the edge.