Microwave Imaging Diagnostics in Fusion Plasmas: Progress and Perspectives
Microwave diagnostics will be one of the few diagnostic techniques that can be operated in future fusion devices. In the past, they have contributed significantly to the understanding of the plasma dynamics, in particular electron cyclotron emission (ECE) and reflectometry. While these provide 1D measurements of plasma electron temperature and density along a line of sight, the advancement of electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) allows to obtain 2D images with high temporal and spatial resolution. Recent technological improvements will not only reduce the overall dimensions of these systems, thereby fulfilling requirements of future fusion devices, but also increase their sensitivity, reduce their costs, and ease maintenance which increases operational time of the devices they are installed on. This paper tends to give an overview on electron cyclotron emission diagnostics and reflectometry in general, discussing ECEI and MIR in more detail, including the latest developments, and also providing a perspective on the future.