Study of an extremly thin-diamond window for terahertz traveling wave tubes

This paper describes the design and fabrication of an extremely thin-diamond window for terahertz traveling wave tubes. To reinforce the mechanical properties of the micro-crystalline diamond (MCD) incorporated with ultra-nano-crystalline diamond (UNCD), a 60 pm thick, seven-layered composite diamond film was fabricated. It was cut into window disks without lapping and polishing, which were then made into window assemblies. Vacuum tests of the window assemblies showed no occurrence of window cracking or other damages resulting from mechanical stress, while leak tests did not found apparent air leaks either. These testing results show such a composite diamond possesses adequate mechanical properties for the application of THz wave TWT windows. This work provides a novel approach for the fabrication of extremely thin-diamond windows for THz TWTs.