The effect of potential beam energy on the performance of linear beam devices

The potential energy stored in a bunched electron beam is calculated using analytical and numerical methods. The ratio of stored potential energy to the total beam energy
W_{p}/W_{0}
increases rapidly with the degree of bunching and with decreasing beam filling factor
b/a
.
W_{p}/W_{0}
is proportional to the beam perveance and independent of the beam voltage, as long as relativistic effects are neglected. In a velocity-modulated linear beam-type device, such as a klystron or a traveling-wave beam tube, stored potential beam energy affects both the bunching process and the process of dc to RE energy conversion adversely. For maximum conversion efficiency
W_{p}/W_{0}
should be kept as low as possible. Several ways of reducing
W_{p}/W_{0}
are discussed.