Design, Simulation and Construction of a Low-Density Fixed-Frequency Refleloctometer

Since some tokamaks such as Taban are currently working with low density plasma, a fixed frequency reflectometer system was designed and constructed to monitor plasma production within the vacuum vessel. In this paper, the detail of design, simulation and construction of the system is presented. Moreover, some experiments which have been made for the evaluation of the system performance is reported. The system consists of a circular waveguide-antenna to both transmit and receive the microwave as well as a fully integrated system for measuring the phase difference between transmitted and received signals. To make sure of the perfect performance of the constructed system, some experiments were conducted to individually evaluate system operation. In order to verify the obtained results, all the mentioned experiments were simulated using CST software and the simulation results were compared with those obtained from the experiments. Good agreements were observed between simulation and experimental results, implying the high reliability of the system operation. After approval of the system performance, the system was implemented in Taban Tokamak to monitor the plasma production. Using the reflectometer outputs, the plasma density was estimated.