3D large-signal analysis in beam optics analyzer

The standard approach to obtain the spent beam exiting an IOT output cavity is to assume a beam profile at the cavity entrance and use a 2D large signal code such as Tesla or Nemesis to modulate the beam. These codes rely on integration of equivalent circuit equations coupled with the Lorentz force equations for particle trajectories. They employ a 2D model for the circuit fields and a 2D Poisson solver. They are very efficient and give very good results. However, they are not convenient to use for IOT devices. An injected RF modulated beam profile is either provided analytically or computed elsewhere by another code. More complex 3D geometries such as a multiple beam configuration could not be analyzed by such 2D large signal codes.