Relativistic electron-beam-focusing experiments employing axial loads

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Abstract
The self‐focusing of intense relativistic electron beams in vacuum diodes relies upon beam‐anode interactions to govern the time required to pinch the beam. Experiments performed at various laboratories have yielded sweep‐in velocities of ∼1–2 mm/nsec. These low velocities result in the loss of a large fraction of the energy of the REB outside the pinch region.. As a means of increasing the sweep‐in velocity and also improving beam centering and reproducibility, experiments were performed utilizing axial loads, either resistively or inductively isolated from the main low‐impedance cathode. These experiments were carried out on various high‐power generators, and average sweep‐in velocities of up to ∼6 mm/nsec have been recorded for modest amounts of current on axis (≲10% of the generator current).