Simulation of reflectometry density changes using a 2D full-wave code

Broadband reflectometry is used to obtain density profiles in fusion plasma s using waves reflected at different plasma layers. The reflected signal ca n be severely affected by plasma fluctuations and/or fast density changes. In order to understand the plasma response, a finite difference time domain two-dimensional full wave code was developed. The code was used to study t ypical situations of fusion plasmas where important profile movements occur : when a rotating magnetic island is present and during an ELM. The numeric al results are in good agreement with experimental results obtained in ASDE X and ASDEX Upgrade in the situations above. Our study demonstrates that co ntributions from the plasma movements are important and should be taken int o account to obtain accurate profile measurements. (C) 2001 American Instit ute of Physics.