Formation and transport of low-voltage, space-charge dominated sheet electron beams for high-power microwave devices

Summary form only given, as follows. Sheet electron beams have the potential to make possible higher power sources of microwave radiation due to their ability to transport high currents, at reduced current densities, through a single narrow RF interaction circuit. We will discuss experimental investigations of the formation of an elliptical sheet beam using magnet quadrupoles and a round-beam electron gun. Features of this configuration include a low-cost, commercially available Pierce gun (10 kV, 2 A, r/sub b/=0.3 cm) and a lens system consisting of four tunable magnetic quadrupoles with modest field gradients (B/sub q//R,/sub q/<60 G/cm). Three-dimensional envelope and particle-in-cell simulations indicate that this method can generate highly elliptic output beams (a=2.7 rm, b=0.1 cm), with variability in final beam size, for laboratory experiments on sheet beam transport. We also will present the results of particle-in-cell simulations of the transport of sheet beams in long-period offset-pole periodic magnet arrays. While the stability of sheet beams in short-period arrays has previously been established, the extension to longer magnet periods indicate that side-focusing of space-charge dominated sheet beams is more problematic than beam stability. However, long-term (>20 periods) stable transport is demonstrated for /spl lambda//sub m/=1 cm for a 2 A, 10 kV elliptical beam with a=2.7 cm and b=0.05 cm.