Nickel and iron as attenuator materials for helix TWT

Abstract

Coating of lossy material is done on the helix support rods to absorb reflections in a helix travelling wave tube. Carbon is a very commonly-used material used for this type of coating, but other materials may also be employed for this purpose. In the present work coatings of carbon, nickel and iron have been done and evaluated for the attenuation performance at microwave frequencies. Three alumina rods have been coated with different methods to characterize them for attenuation. One alumina rod has been coated with carbon using the pyrolytic deposition method, while two others have been coated with iron and nickel using the electro-deposition method. An experimental set-up involving a narrow-height waveguide with a hole was used to measure the attenuation of the coated rods at 6.0 GHz frequency.