Edge density profile measurements by X-mode reflectometry on Tore Supra
A broadband reflectometer operating in the frequency range 50-75 GHz has been developed on Tore Supra to measure electron density profiles at the edge. The system uses extraordinary mode polarization and performs routine measurements in 20µs with heterodyne detection to ensure high dynamic range sensitivity. It allows separate phase and amplitude information of the signal. The density profiles are fully automatically calculated from the raw phase. The initialisation is done with automatic detection of the first cut-off from the amplitude of the reflected signal with an accuracy of up to 0.5 cm. The profiles are not part of public database of Tore Supra and can provide details of density structures better than the centimeter range. The high reliability of the measurements for various plasma conditions make this diagnostic an ideal tool to study specific edge plasma physics with given examples on detached plasma behaviour and antenna-plasma coupling processes for ion cyclotron resonant frequency and lower hybrid heating powers. It also is shown how the presence of suprathermal electrons may perturb the measurements.
Bibliographic Reference: An article published in: Plasma Physics and Controlled Fusion, Vol.43 (2001), pp.429-441
Record Number: 200113871 / Last updated on: 2001-10-05
Original language: en
Available languages: en