Observation of Multiple Modes of Interior Density Turbulence in the TEXT-U Tokamak

Two distinct broadband modes of density turbulence propagating in the electron drift direction are simultaneously observed in the first complete measurement of the wave number frequency spectrum S(k,omega) in the interior of the TEXT-U tokamak plasma. A drift wave-type mode with a peak in the wave number spectrum at k(theta) similar to 4.5 cm(-1) is found on both sides of the magnetic axis. A long-wavelength mode with k(theta) less than or equal to 2 cm(-1) is found only on the low field side of the tokamak. The results resolve apparent discrepancies in previous turbulence measurements Confinement properties of TEXT-Lr an consistent with the transport predicted by the observed drift wave-type (k) over bar(theta) = 3 cm(-1) [S0031-9007(99)08765-7].