Plasma frequency reduction factors in electron beams

The electron plasma frequency reduction factor has proved to be a fundamental design parameter in all types of microwave tubes employing long electron beams. This factor is here calculated for a variety of beam shapes and drift-tube cross sections, and the results are presented in a series of graphs. One interesting result is that the reduction factor for an annular beam depends primarily on the width of the annulus and is relatively independent of the radius of curvature of the beam.