Hot phase velocity measurements and modeling for a broad band TWT

Summary form only given. We have made measurements of and modelled cold and hot phase velocities for the custom-made XWING broadband traveling wave tube. The TWT used in this investigation, termed the XWING TWT (for experimental Wisconsin Northrop Grumman TWT), is a research version of a product manufactured by Northrop Grumman. This two-stage, helical TWT provides a moderate gain of 20-30 dB over a frequency range of 2-6 GHz. The second stage of this TWT is configured with sensors placed at various points along the axis of the tube. These sensors allow the measurement of wave amplitude and phase to be made at a number of points along the axis, yielding additional wave evolution information not readily obtained from other TWTs, whose only wave information is available at the input and output of the device. By capturing the signal from two of these sensors, we have measured the cold and hot phase velocities in the 2-6 GHz range.