Feasibility study of developing central-chord microwave interferometer of Alvand Tokamak to a multi-channel system

Microwave interferometers are among the most important diagnostic tools in measuring the electron density of tokamak plasma. However, single-channel interferometers only measure the linear average of the plasma density along the central chord of the tokamak cross-section and do not provide accurate information on the spatial distribution of the density. Multi-channel microwave interferometers allow for the measurement of the radial profile and spatial distribution of the tokamak plasma density. This information is essential for studying magnetic instabilities, optimizing energy transfer, and controlling the plasma. Currently, the interferometer in the Alvand tokamak is single-channel and only measures the linear average of the plasma density along the central chord. This limitation reduces the accuracy and comprehensiveness of the plasma data. The main objective of this paper is to design a multichannel interferometer system for the Alvand tokamak that can measure the radial profile and spatial distribution of electron density. This system is designed based on five symmetrical channels for transmitting and receiving microwave beams along the main radius and sub-chords of the Alvand tokamak to provide more comprehensive information on the spatial structure of the plasma. For efficient beam transmission with less loss, the use of tapered waveguides with larger dimensions was proposed. The requirements of spatial constraints for installing wave transmitting and receiving equipment around the vacuum chamber, measurement and calibration requirements of the proposed multi-channel interferometer were also examined. The proposed design will provide a significant improvement towards completing the active remote diagnostic systems of the Alvand Tokamak.