Turbulent density fluctuations in the TCA Tokamak

The results of an investigation into the spectral characteristics, spatial structure and scaling with plasma parameters of low frequency density fluctuations in ohmically heated TCA plasmas are presented. A substantial fraction of the spectral energy is found to be associated with fairly small perpendicular wave numbers, (k perpendicular to )<or approximately=2 rad/cm. Profile measurements indicate that the edge is dominated by low frequencies (<or approximately=100 kHz) whereas the higher frequencies (>or approximately=100 kHz) dominate in the interior. An asymmetry between the low and the high field side is observed, confirming observations on two different machines. The estimated local level of the fluctuations and its scaling with plasma parameters is found to follow Kadomtsev's mixing length rule (B.B. Kadomtsev, 1965) n/n equivalent to ((k perpendicular to )L n ) -1 .