Dispersion properties of spiral deflecting systems

The dispersion properties of spiral deflecting systems of traveling wave electron ray tubes were analyzed. Systems with rectangular, circular and elliptical cross sections are considered. It is shown that the cause of the dispersion of the phase holding time in spiral deflecting systems with homogeneous dielectric is the electromagnetic bond between the individual sections of the spiral. To reduce this dispersion systems consisting of a spiral placed between two screens are used, while the dispersion in the systems with extensive elliptical and rectangular cross sections is less than for circular spiral deflecting systems. In deflecting systems with different dielectrics in the internal and external regions of the spiral the dispersion may arise because of the redistribution of the electromagnetic field and its value depends on the ratio of the dielectric permeabilities and the transversal dimensions of the system. Simple approximate expressions to determine the slowing down for very low and high frequencies are presented.