A 3D Finite-Element Modeling Tool for Multipacting Analysis

Strong radio-frequency electromagnetic fields in the high-power components used in colliders can induce a resonant cascade of particles near internal surfaces (called multipacting) ¿ which can lead to poor performance and device failure, in some cases limiting the power than can be handled to a fraction of the design requirement. Existing tools for analyzing this phenomenon have limited accuracy, and are inefficient and difficult to use, particularly on complex three-dimensional structures. This project will create a new capability that performs both the field solution and particle tracking on the same boundary-conforming finite-element mesh, thereby avoiding errors from inaccurate surface modeling and field interpolation, which plague existing tools. The result will be a production-level capabilility for multipacting analysis in complex two- and three-dimensional structures. In Phase I, a prototype capability was created that manages the calculations necessary for multipacting analysis, including the generation of radio-frequency electromagnetic field solutions, an automated search for resonant particle orbits using a new adaptive particle tracker, and the accumulation and presentation of multipacting statistics. This capability was encapsulated within a new specialized environment hosted by a commercial analysis package and was benchmarked against established solutions for coaxial feed lines, a superconducting radio-frequency cavity, and a bunching cavity. Phase II will improve particle tracking by adding support for higher-order curvilinear elements, interactive visualization of particle orbits, adaptive mesh refinement, and a calculation for verifying multi-particle multipacting. Commercial Applications and other Benefits as described by the awardee: The new multipacting analysis tool should enable more rapid development, lower costs, and more robust device designs for a broad class of high-power radio-frequency systems used in commercial and government applications. These systems include microwave tubes, radio-frequency ¿plumbing¿ for high power applications such as radar and microwave telecommunications links, commercial accelerators, and others. In particular, DOE projects such as the International Linear Collider require high-power, radio-frequency accelerator components that are at risk of failure due to electron multipacting, yet existing analysis software has only limited utility in the quest for hardware designs that avoid this problem