Measurements of the density-temperature cross-phase angle of turbulent fluctuations and comparison to theory
The experimental validation of turbulence models is a critical part of developing a predictive understanding of plasma transport. Models based on the non-linear gyrokinetic equations are currently the most well understood and experimentally validated models of turbulence available. However, models of reduced complexity are required in order to make useful transport predictions for future machines. Development of such models has made steady progress, however, there has not been extensive validation of these models against measured turbulent quantities and their trends. It is interesting to compare model predictions, where available, for turbulent quantities which are directly related to the heat flux, such as fluctuation amplitudes and crossphase angles of fluctuating quantities. The most experimentally accessible cross-phase quantity is that between the temperature and density fluctuations αnT, and this has previously been demonstrated using a reflectometer for the density fluctuation information and a radiometer fortemperature fluctuation information [1, 2, 3].