A New Hybrid Method for High-Order EM-PIC Simulations

Wave Computation Technologies, Inc. (WCT) proposes to develop a new commercial electromagnetic particle-in-cell (EM-PIC) software package based on a 3-D hybrid technique that combines two efficient algorithms, (a) the enlarged cell technique (ECT) and (b) the spectral-element time-domain (SETD) method, as a high-order solver for EM-PIC simulations. This hybrid technique overcomes the well-known limitation of existing EM-PIC solvers due to their stair-stepping approximation. The proposed hybrid method uses domain decomposition to divide the problem into SETD regions with coarse structures and ECT regions with fine structures. As the SETD method has spectral accuracy and the ECT method has second-order accuracy, the overall convergence of this EM-PIC solver is better than second order. In Phase I the team has already developed and demonstrated the prototype of this method. Specifically, we have integrated the ECT with the particle-in-cell calculation, and have achieved the second-order global convergence. The typical computation time for a problem with 5.45 million cells and 1600 time steps is approximately 14 minutes on a desktop computer (Pentium-D 2.8GHz, only 1 CPU is used). This speed is believed to be unprecedented. In Phase II, the proposed 3-D hybrid numerical EM-PIC solver will be integrated into an existing commercial platform to produce a new commercial package, Wavenology PIC. It promises to effectively mitigate spurious effects caused by the stair-stepping approximation in the conventional EM-PIC simulation method. The commercial code will be complete with particle emission and propagation. The algorithm will be scalable, stable and globally at least second order accurate for curved geometries. Issues such as self force, grid heating, non-physical radiation and self heating will be mitigated to globally second-order convergence.