Reversible periodic magnetic focussing system

Increased perveance of the electrons flow formed by reversible periodic magnetic focusing system of klystrons shortens the reversal zones. The advance of the high-perveance electron flow is also achieved with the modified design of the pole pieces in the system comprising successive oppositely polarised permanent magnets. They are separated by magnetically soft pole pieces exhibiting opening for the electron beam passage. The holes contain grids with cells of magnetically soft material and having magnetic, thermal and electric contacts with the pole pieces. The ratio of diameters of cells (3) in the grids (2) and of the pole pieces (1) is chosen as a function of grids thickness, azimuthal spacing between the cells, and also depending on centres spacing of cells and pole pieces. The uniformity of magnetic field distribution in gaps between the grids (2) is controlled by height of projections (6) of pole pieces (1), diameter and spacing of the latter. Reduced work in the fabrication of the reversible periodic magnetic focusing system is achieved by substituting the radially magnetised permanent ring magnets (7) by longitudinally magnetised units. The invention is used in accelerators too.