Optimal periodic permanent magnet structure for electron beam focusing tubes

摘要

In the preferred embodiment a plurality of toroidally shaped magnets of similar size and configuraton are placed in a stack side-by-side in coaxial alignment. Alternate magnets in the stack are magnetized so that the magnetic dipole moment of each is oriented in the radial direction. An axial magnetized toroidal magnet is disposed between each pair of adjacent radially magnetized magnets. The magnetic orientation of the succesive toroidal magnets of the stack rotates continually in one direction in increments of 90 DEG or pi /2 radians from the magnet at one end of the stack to that at the other end.