Reliability study of TWT output RF window

Rome Air Development Center Computer-Aided Systems Engineering Branch (RBES) has documented an in-house effort to evaluate the structural reliability of the output waveguides window on a Traveling Wave Tube (TWT). This window acts as a seal between the TWT's vacuum envelope and output waveguide. Its purpose is to prevent any loss due to leakage of the vacuum while allowing passage of the microwave signal. This particular disk-shaped window is constructed of a ceramic material, beryllia, and contains an inner ring of copper and an outer ring of Monel K-500 (70 to 30 nickle-copper). It was suspected that excessive thermal stresses associated with the very high operating temperatures by this window has caused it to fail. Finite element analyses, along with material failure theories were used to determine the window's response to a time-dependent heat source and operating heat sink temperature.