Reflectometry: A Reliable And Sensitive Plasma Diagnostic For Density Profile And Turbulence Measurements On Tore‐Supra

A set of four reflectometers has been installed on Tore‐Supra to measure the density profiles and the properties of density fluctuations with good spatial resolution. Fast swept X‐mode reflectometers covering the range 50 to 155 GHz provide reliable and accurate measurements of the whole density profile from the edge on the outer side up to the core on the high field side even during large and fast profile evolution. Precise evaluation of the density profile is crucial for particle transport studies. A particular feature, a local peaking, has been observed in the core during ohmic discharge. Density fluctuations are measured with three different techniques. The classical fixed frequency method looks at large scale fluctuations (kr < 3 cm−1) . It measures the radial profile of fluctuations and can detect density perturbation associated to high frequency modes. A new method has been validated to measure the radial profile of small scale density fluctuations from fast FM‐CW phase reflected signal. This method could also retrieve the radial wavenumber spectrum. The last method Doppler reflectometry is based on back scattering. It measures the poloidal rotation and fluctuations amplitude at different poloidal wave numbers (3 < kθ < 20 cm−1). This collection of diagnostics achieves complementary measurements from the low to the high field side of the discharge and from large to small scale.