Millimeter-wave gain experiments with a wide-band omniguide traveling-wave tube

We report the results of recent high power electron beam tests of a novel W-band traveling-wave tube (TWT) amplifier based on a slow-wave cylindrically-symmetric photonic band gap (PBG) structure called the "omniguide". Dielectric PBG TWTs have a wide operational frequency band (more than 20%) and may be favorable for use at millimeter wave frequencies due to shortcomings of conventional metal TWT technology. The omniguide structure\´s design and fabrication were reported elsewhere [1]. For the tests, we passed the 1 A, 110 kV, 2 μm long electron beam pulses through a 0.92 mm diameter hole in the omniguide inner dielectric tube. A 100 mW source which was tunable from 91 to 101.5 GHz was used to drive the tube. A gain of about 2.5 dB per cm has been demonstrated in well reproducible pulses.