Image charge focusing of relativistic electron beams

Abstract
Experimental results are reported on the transport of a relativistic electron beam by image charge effects. The transport system consisted of a cylindrical metal tube periodically interrupted by transverse conducting grids with high transparency. Partial cancellation of the beam electric fields increased the space-charge-limited current level, allowing propagation in a magnetically self-pinched mode. A 400-keV, 4-kA beam traveled 30 cm in high vacuum through 10 focusing foils. Capture of the beam was almost 100% efficient; beam emittance was not severely degraded during capture and transport. The radius of the self-contained beam was 1.4 cm; the beam position was centered by the image current in the transport tube to within 1 mm. The favorable results imply that image charge focusing could be considered for transport in high-current linear induction accelerators.

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