Advances in millimeter wave/THZ plasma diagnostics instrumentation

Significant advances in millimeter wave and THz receiver and array technology have led to new approaches for the visualization of density and temperature fluctuations inside the core of high temperature plasmas. Electron cyclotron emission imaging collects millimeter wave electron cyclotron emission from the plasma and images it onto a planar mixer array to form 2-D images of electron temperature fluctuations. Illuminating the plasma with millimeter waves, microwave imaging reflectometry images the plasma cutoff layer onto a planar mixer array and thereby spatially resolves density fluctuations on the extended plasma cutoff surface; the use of multiple frequency illumination results in the formation of 2-D density fluctuation images. Collective scattering approaches at THz frequencies can resolve density fluctuations deep into the plasma core that are not accessible via reflectometry.