UC Davis PDG:2D Turbulent Fluctuation Structures on RTP

The spatial distribution of the electron temperature fluctuation amplitudes can be measured on a shot to shot basis, when the sample volumes of ECEI are scanned through the plasma minor cross section. When the fluctuation amplitudes (dT/T) are scaled in colors, the 2D image is constructed and shown above. It is obtained at Ip=60 kA, ne=1.5x10e19 m-3. The horizontal axis R is the major radius of the tokamak (RTP) in cm, and the vertical axis is the vertical position (z, to scale) of the plasma volume. The yellow cross represents the center of the vacuum vessel.
 
 




The following two 2D image are obtained at  , and  . From the left Figure, it is seen that the MHD fluctuation peaks at the q = 2 radius (r ~ 5 cm), as expected. From the right Figure, it is seen that the distribution of turbulent fluctuations is not correlated with that of MHD fluctuations. Prominent peaks with strong fluctuation amplitudes are seen, showing that the fluctuation is not uniformly distributed. The extent of the peak structures is comparable to the plasma minor radius. As the results are obtained over long period averaging, the structures must be stationary in space to remain.

For further technical details, and ECE Imaging measurements and results from RTP, please examine the following links: 

*Further technical details on the RTP ECE Imaging system
*High resolution measurements of electron temperature profiles
*Electron temperature fluctuation spectra
*Electron temperature fluctuation dispersion relations
*Electron temperature fluctuations as a function of plasma current and density
*2D structure of electron temperature fluctuations

The unique features of the ECE Imaging diagnostics derive from the use of wideband, low cost monolithic and hybrid Schottky diode mixer arrays. Follow the links below to learn more about both the technology and the techniques employed in ECE Imaging. 

*Imaging array design and fabrication
*Correlation Measurements

UC Davis has fabricated and installed multichannel ECE Imaging systems on other fusion plasma tokamaks across the world. Follow the links below for a description of the systems involved, and to sample data collected with these systems. 

*ECE Imaging on the TEXT-U tokamak in the U.S.A.
*ECE Imaging on the TEXTOR tokamak in Germany

emailComments to: Bihe Deng