Concentration and Guidance of Intense Relativistic Electron Beams

None of the field-emitting cathodes using sharp points or edges presently being used in producing pulsed intense relativistic beams has any particular advantage over a smooth well-rounded form having the same over-all dimensions when the interelectrode distance is small enough for the current to be space-charge limited. A new method is reported herein for increasing the current substantially and concentrating the increased current into a beam with a diameter less than 2 mm. A small-diameter dielectric rod or tubing inserted into the cathode and extending towards the anode forms a pinched discharge in a thin layer near the dielectric surface concentrating the current with the pinch and guiding the beam in any desired direction.