End-to-end electron beam modeling in O-type devices

Summary form only given. End-to-end simulation of an electron beam is described using the example of an EIK amplifier. Computations are performed using a general purpose, relativistic 3D/2D steady-state beam modeling tool called UGUN. A multi-element, gridded Pierce-type gun is used to launch a beam into a permanent magnet focusing field of approximately one tesla (greater than twice the Brillouin value), achieving an area convergence ratio of 100:1. Thermal beam effects, both energy spread and angular launch with respect to the surface normal are included. After energy modulation is introduced midway within the final cavity circuit, the beam continues into a multistage depressed collector within which both elastic and inelastic secondary electrons are generated. Computational results are found to compare favorably with the measured result obtained with an experimental EIK. Assessment of the thermal distribution impact upon beam focusing is aided by a provision for generating detailed enclosed-current contour plots. Algorithms employed in the simulation model are described including treatment of the thermal beam launch and secondary emission. Methods for treating electron beams in long drift tubes are also discussed.