Propagation of wiggler focused relativistic sheet electron beams

Abstract

A recent design concept for millimeter-wave free-electron lasers [J. Appl, Phys, 60, 521 ( 1986)] would require the stable propagation of a sheet electron beam through a narrow waveguide channel. Experimental results reported in this article support the feasibility of such a configuration by demonstrating the stable propagation of relativistic sheet electron beams through a narrow waveguide gap (3.2 mm) using focusing by a short-period electromagnet wiggler. 90% of the electron current in a loo-keV sheet electron beam was transmitted through a S-cm-Iong channel with peak wiggler fields of 800 G. Almost 80% of a 400-keV beam was similarly confined with a 16oo-G wiggler field. The data were consistent with single electron trajectory models, indicating that space-charge effects were minimal. No evidence of beam breakup or filamentation instabilities was observed.