Preliminary results of the ORNL swept dual-frequency X-mode reflectometer for TFTR

Summary form only given. The edge density profile can play an important part in determining the plasma confinement and the coupling of ICRH power to the plasma. To study the effect of the ICRH power on the plasma, a swept dual-frequency reflectometer has been installed and tested on the TFTR (Tokamak Fusion Test Reactor). This reflectometer uses a dual-frequency differential phase measurement to reconstruct the edge density profile, with the advantage of reducing the fringe count and the errors due to fringe skipping. The X-mode of propagation is used because of its ability to probe the edge of the plasma starting at the local electron cyclotron resonance frequency with a minimum of frequency range and its inherently good spatial resolution at such low densities.