Millimeter wave diagnostics of materials and melts

Diagnostics of materials in high-temperature, optically inaccessible environments can be reliably achieved with millimeter-wave methods and components. A 137 GHz heterodyne receiver using a thermal return reflection (TRR) technique and ceramic waveguides tested to 1500/spl deg/C have been used to demonstrate the capability to measure temperature, emissivity, viscosity, and salt layer formation in laboratory and pilot scale melter tests.