Detection of lower hybrid waves within a plasma by microwave scattering

The spatial distribution and intensity of electrostatic waves injected into a hot plasma may be inferred from the scattering of millimeter microwaves. We report measurements on the 30 degrees scattering of 8.6-mm microwaves by a 500-W, 2.45-GHz slow wave excited in a linear plasma by a phased array of two waveguides. From the magnitude of the scattered signal and auxiliary measurements with probes, we infer that a large fraction of the injected power penetrates to the center of the overdense test plasma.