Evolution of PIC Simulation with Applications to RF Multipactor

Plasma simulation started in the 1960s and was formalized in subsequent decades by Birdsall and Langdon and Hockney and Eastwood. We will provide an overview of key milestones that contributed to the robust state of modern particle in cell (PIC) simulation tools and discuss some remaining challenges for the field. Multipactor and its transition to gaseous ionization breakdown remain one of the most significant limitations in RF device operation, particularly at high power. Nonlinear effects can couple multiple carrier frequencies, cause instabilities and dispersion, and result in temporary failure as well as permanent damage. These phenomena are relevant to conducting and dielectric surfaces, in devices ranging from communications to high power microwave sources, to accelerators and even high gradient microwave circuits and devices. This work is part of a larger effort which includes development of standardized platforms in planar, coaxial, and stripline configurations, with both computational and experimental analogs to enable validation and develop analytic and predictive capability integrated with well-tested experiments. Here, we focus on the computational modeling efforts. We examine the process of initial multipactor growth, surface heating and gas desorption, and subsequent evolution to ionization breakdown. We look at a variety of mitigation schemes, from spatio-temporal signal modulation and wave mode configuration to surface morphology and materials properties. We will even show the indications of two-stream instability (Birdsall’s thesis topic) in the transition from multipactor to ionization discharge breakdown.