Particle-in-cell modeling of large plasma devices

In many plasma applications there is a need to simulate large plasma devices via kinetic means. This arises from the fact that the Electron Velocity Distribution Function in these devices is non-Maxwellian and therefore a fluid treatment is insufficient to accurately capture the physics as well as the global engineering performance. The method of choice for many fully kinetic simulations has been the particle-in-cell (PIC) technique, because it is relatively easy to implement and can be parallelized effectively over many processors. However, in order to faithfully replicate plasma physics, PIC codes that use standard explicit schemes are constrained by the requirement to resolve the short length and time scales associated with the plasma Debye radius and plasma frequency respectively. This makes it extremely challenging to perform long time 2D PIC simulations for large plasma devices. For this reason, many 2D kinetic simulations of plasmas have been limited to small or artificially scaled systems. Energy conserving or implicit methods have to be used to remove these limitations. At PPPL we have developed two codes EDIPIC-2D and LTP-PIC 3D. EDIPIC 2D is an open-source code that has many features for simulations of practical devices (e.g., we incorporated complex geometry and complex boundary conditions) and has been used for modeling of several plasma devices. LTP-PIC 3D is a high-performance scalable PIC code which incorporates best programming practices and multi-level parallelism. This code was upgraded to operate efficiently on the latest CPU/GPU architectures for additional performance improvements. Simulation results from this upgraded code are benchmarked against other codes, and where available, analytical theory. Multiple examples of use of both codes as applied to plasma processing applications, such as capacitively coupled plasmas, inductively-coupled, electron beam produced plasmas, hollow cathodes.