Advances in high performance simulation software for vacuum electronics devices

We present recent developments in the VSim software for modeling vacuum electronics and semiconductor devices on large scale parallel and GPU computing platforms. Recent emphasis has been on capabilities needed for modeling high power gyrotron devices, where high mode numbers and closely spaced competing modes require much greater geometrical and physical fidelity than for other vacuum electronics devices. Also of concern in modeling such devices is the simulation tuning techniques needed to operate very close to mode cutoff, when discrete representation dispersion is not perfect, and issues relating to the boundary condition treatment for the geometry radiation, to prevent backward flowing power that disrupts the mode growth behavior. We have also worked to improve the physical algorithms and fidelity of lossy materials in the MIG gun and taper regions. We also discuss the practical application of external circuit models to the MIG gun region, and improvements to the software to allow for more general circuit models in both electromagnetic and electrostatic simulations. We show how the external circuit may be of importance in the simulation of a MIG gun´s low frequency oscillations. Here the use of GPU computing provides speed-up, which we are then able to translate to extended physical simulation time, greatly aiding in the study of such long time scales. We discuss integration of thermal modeling with electromagnetic modeling, including new time and space resolved particle heating sources, using our TruCouple technology, which simultaneously models the disparate electromagnetic and thermal time scales in the same simulation. Finally, we demonstrate use of the VSim software to model semiconductor physics, with simple examples of MESFET´s and other traditional structures. Work partially supported by DOE Phase II SBIR grant DE-SC0004436.