PERIODIC FOCUSING AND PONDEROMOTIVE STABILIZATION OF SHEET ELECTRON-BEAMS

Particle simulations compare the behavior ot nonrelativistic sheet ele ctron beams in uniform static and nonuniform time-harmonic magnetic fi elds. The time-harmonic fields are equivalent to periodically cusped m agnetic (PCM) fields. While the sheet beam in a uniform field exhibits diocotron instability, the PCM-focused beam is stabilized by ponderom otive forces, in agreement with recent analytic predictions [J. Appl. Phys. 73, 4140 (1993)]. Mismatched PCM-focused beams exhibit envelope oscillation and initially rapid emittance growth followed by a region of slower increase, in agreement with a recent semianalytic Fokker-Pla nck model.