Frequency Range Determination for Reflectometry System in Alborz Tokamak Using 2D FDTD Simulation

Abstract

Reflectometry is a plasma diagnostic technique similar to radar. Microwaves are lunched into the plasma and reflected at the critical surfaces. By receiving the reflected microwave signals and comparing them with the lunched waves, the plasma density profile and its fluctuations can be obtained. Multiple-fixed-frequency reflectometry is one of the methods which considered determining Alborz Tokamak plasma cut off layers position and plasma density profile. In order to design components of the reflectometer, the main parameter which should exactly be determined, is the range of microwave frequency. For the mentioned purpose, a 2D code is used to simulate plasma profile reconstruction in Alborz Tokamak. The code uses the finite-difference-time-domain method with a perfectly-matched-layer absorption boundary to solve Maxwell’s equations. A 1D formula also is used to verify values resulted from the simulation. The good agreement between calculated and simulated values shows the high accuracy of the simulation. With respect to the simulation results, the appropriate range of frequency is determined and the reflectometer components can be designed according to this frequency range.