CVD diamond rod and its application in the high power TWT

In a helix type TWT, dielectric material is used to support the helix and provide a thermal path from the helix to the barrel. The dielectric support material, however, undesirably alters the electric field pattern of an RF wave on the helix, reducing the field strength inside the helix where the electron beam-wave interaction takes place. Thus, to optimize the beam-to-RF conversion efficiency, it is most desirable to use a low dielectric constant material and a minimum amount of material to support the helix. Diamond is an electrical insulator and is also a good thermal conductor, having a thermal conductivity of approximately six times that of copper. Thus in addition to providing the required attenuation within the slow wave structure, the use of diamond also provides a good thermal path for the removal of excess heat generated during operation of the tube from its interior. A breadboard TWT recently demonstrated CVD diamond can replace the traditional BeO rod and be used in the wideband high power TWT to improve the heat dissipation greatly. The technology is very simple and the cost is very low.