Dynamics of the space-charge-limiting current in gyro-type devices

The Air Force Research Laboratory is investigating the dynamic interactions which occur between the growing electromagnetic waves generated in a gyro-type device, and an electron beam (e-beam) with nonzero perpendicular velocity operating near the space-charge-limiting current. Particle-in-cell (PIC) codes are used to perform simulations of the transverse electric (TE)/sub 01/ mode, and results are presented. Initial results show that beams of this nature suffer from a time-dynamic onset of the space-charge-limiting current instability at values below those predicted from analytic theory. This produces a beam time-dynamic pulse shortening, thus placing an upper limit on the power and pulse length of gyro-type devices.