Experimental Validation of Slow-Wave Phenomena in Curved Ring-Bar Slow-Wave Structure

• Published in: IEEE transactions on plasma science Vol. 44; no. 9; pp. 1794 - 1799
• Main Authors: Zuboraj, Muhammed, Chipengo, Ushemadzoro, Nahar, Niru K., Volakis, John L.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-09-2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bandwidth; Coupled transmission lines (TLs); curved ring-bar (CRB); Dispersion; Electric power lines; Electron beams; Electron tubes; Geometry; Impedance; Plasma physics; Power supply; slow-wave structures (SWSs); Transmission line measurements; traveling-wave tubes (TWTs); Velocity
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/TPS.2016.2591831

Curved ring-bar (CRB) slow-wave structure (SWS) has been presented before in order to design an SWS for high-power and wideband traveling-wave tube in S-band. It was analyzed using the coupled transmission line theory and predicted to deliver 1-MW output power across 1.8-2.4-GHz bandwidth. However, the slow-wave characteristics were not experimentally validated through measurements. In this paper, we present ω -β measurement results to experimentally demonstrate that the CRB structure is providing the predicted slow-wave characteristics at the S-band. A novel synthetic technique is used to determine the w - β relation using a six-period fabricated CRB structure. The measurement results exhibit a phase velocity of 0.7c-0.75c across 2-2.5 GHz with a maximum error of less than 5%. In addition, the measured on-axis interaction impedance was >43 Ω across the specified frequencies implying satisfactory agreement with theoretical predictions.