Experimental Determination of Helical-Wave Properties

The properties of the wave propagated along a helix used in the traveling-wave amplifier are discussed. A description is given of measurements of field strength on the axis, field distribution around the helix, and the velocity of propagation. It is concluded that the actual field in the helix described is slightly weaker than would be predicted from the relations presented by J. R. Pierce for a hypothetical helical surface.