Confined Electron Flow in Periodic Electrostatic Fields of Very Short Periods

By utilizing the centrifugal force of an electron, resulting from a magnetic field in the cathode plane as a restoring force, an electrostatically-confined beam flow can be obtained through the strong focusing of a periodic electric field. Because of the extremely steep nature of the potential valley derived from its particular force field, the focusing scheme is far more stable than any previous ones. A uniform magnetic field threading the cathode is employed when a very thin, hollow beam is to be focused. By using a radially varying magnetic field, the focusing scheme can be applied to thick hollow beams, of low as well as of high perveance. Experimental results indicate that the focusing performance obtained is much less critical than that obtained with a periodic magnetic field which has been recently tested extensively.