Observation of long wavelength turbulence in the TCA Tokamak

Broadband density fluctuations have been investigated in the TCA Tokamak by means of the phase contrast method using a CO 2 laser operating at 10.6 mu . This technique is well suited to the observation of large scale fluctuations. Correlation measurements between two detectors viewing different chords of the plasma cross-section show that more than half of the turbulence power is associated with wavenumbers smaller than 2 rad cm -1 .