Performance of a Nano-CNC Machined 220-GHz Traveling Wave Tube Amplifier

• Published in: IEEE transactions on electron devices Vol. 64; no. 5; pp. 2390 - 2397
• Main Authors: Baig, Anisullah, Gamzina, Diana, Kimura, Takuji, Atkinson, John, Domier, Calvin, Popovic, Branko, Himes, Logan, Barchfeld, Robert, Field, Mark, Luhmann, Neville C.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.05.2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplification; Bandwidth; Bandwidths; Blades; Defense programs; Electron guns; Frequency measurement; Frequency ranges; Gain; High gain; Insertion loss; Integrated circuit modeling; Integrated circuits; Klystrons; Millimeter wave; Milling; Milling (machining); MMIC (circuits); Multilayers; nano-CNC fabrication; Nanocomposites; Numerical controls; Performance evaluation; Research projects; Surface roughness; terahertz vacuum electronics; Tolerances; traveling wave tube amplifier (TWTA); Traveling wave tubes; Tungsten; Voltage
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2017.2682159

We report on hot test measurements of a wide-bandwidth, 220-GHz sheet beam traveling wave tube amplifier developed under the Defense advanced research projects agency (DARPA) HiFIVE program. Nano-computer numerical control (CNC) milling techniques were employed for the precision fabrication of double vane, half-period staggered interaction structures achieving submicrometer tolerances and nanoscale surface roughness. A multilayer diffusion bonding technique was implemented to complete the structure demonstrating wide bandwidth (>50 GHz) with an insertion loss of about -5 dB achieved during transmission measurements of the circuit. The sheet beam electron gun utilized nanocomposite scandate tungsten cathodes that provided over 438-A/cm 2 current density in the 12.5:1 ratio sheet beam. An InP HBT-based monolithic microwave integrated circuit preamplifier was employed for TWT gain measurements in the stable amplifier operation region. In the wide-bandwidth operation mode (for gun voltage of 20.9 kV), a gain of over 24 dB was measured over the frequency range of 207-221 GHz. In the high-gain operation mode (for gun voltage of 21.8 kV), over 30 dB of gain was measured over the frequency range of 197-202 GHz. High-power tests were conducted employing an extended interaction klystron.