Low CTE Waveguide for Extreme Thermal Environment

Probes are being sent towards extreme environments of our solar system. The delivery of the science in these environments is a challenge for waveguide systems. The crucial aspects of the design are associated with, and constrained by, the high-temperature, high-radiation exposure and suitable conductivity, requiring advanced materials having a very low Coefficient of Thermal Expansion (CTE). The combination of these requirements led to the selection of carbon-carbon as an ideal material due to its low CTE, good strength, and excellent high temperature characteristics. The purpose of this research was to investigate the feasibility of using carbon-carbon composite for waveguide applications. The characterizations of the mechanical properties are determined through several room temperature tests. A prototype rectangular tube-type assembly was fabricated and copper was plated on the surface of the composite material as conducting surfaces. Specific experiments aimed to study the electromagnetic and physical properties of the composite material were performed. Particularly, the in plane and transverse CTE were examined to determine the proper milling procedure and exploit material qualities. In addition, the machining direction was essential to satisfy the dimensional stability specifications. Outgassing qualification of the composite was analyzed and some coating solutions were also studied. Prototype waveguide frequency range measurements and efficiency were tested to evaluate the compatibility of C/C for waveguide applications.