RF alternate phase focusing in standing-wave electron linacs

In order to minimize the size and weight of the low energy standing-wave linacs and to improve the beam spot as well as the transmission, the RF fields are used for radial focusing without external magnetic focusing devices. By choosing the right phase velocity distribution and by varying the magnitude of the buncher field levels from cavity to cavity, the RF field in the buncher region provides transverse focusing as well as longitudinal bunching and acceleration. The RF phase focusing is more effective by proper choice of an asymmetrical cell geometry in the first cavity. Two linac accelerating structures have been developed by using the RF phase focusing theory and optimizing the shape of the first cavity