Preparation of boron-doped diamond attenuator for W-band folded waveguide traveling wave tube

Attenuators with high thermal conductivity and high fracture strength were required in vacuum electronic devices. In this work, boron-doped diamond film which was used as microwave attenuation material was prepared by DC arc jet chemical vapor deposition (CVD) and the boron-doped diamond attenuator for W-band fold waveguide traveling wave tube (TWT) was fabricated based on simulation results. The results showed that the dielectric constant of boron-doped diamond film was between 7.49 and 8.43, and the loss tangent was around 0.32 in W-band. Meanwhile, the fracture strength of boron doped diamond was 428 +/- 22 MPa in average. In addition, the voltage standing wave ration (VSWR) and S-21 of boron doped CVD diamond attenuator were less than 1.10 and below -50 dB in the range of 85-110 GHz.