The design of periodic magnetic focusing structures

Charts are presented which facilitate the design of permanent-magnet periodic structures for focusing electron beams. These charts include curves showing the peak magnetic field required for periodic focusing in terms of the electron-beam parameters, the magnet and pole-piece dimensions required to obtain this peak field, and the resultant weight of the focusing system. Thus, sufficient information is given to design completely a periodic permanent-magnet focusing structure for a given electron beam. The design of a focusing structure for a 1-watt X-band tube is carried through in detail to exemplify use of the charts.