Modeling Issues for Plasma Processing in SRF Cavities

Modeling Issues for Plasma Processing in SRF Cavities Zenghai Li, Liling Xiao, Cho-Kuen Ng SLAC National Accelerator Laboratory October 3, 2016 1

ACE 3 P – EM Codes for RF Modeling ACE 3 P (Advanced Computational Electromagnetics 3 D Parallel) is a comprehensive set of parallel finite-element electromagnetics codes with multi-physics capabilities in integrated electromagnetic, thermal and mechanical simulation. ACE 3 P has six application modules ACE 3 P (Advanced Computational Electromagnetics 3 P) Frequency Domain: Time Domain: Particle Tracking: EM Particle-in-cell: Multi-physics: Omega 3 P S 3 P Track 3 P Pic 3 P TEM 3 P – – – Eigensolver (damping) S-Parameter Wakefields and Transients Multipacting and Dark Current RF guns & klystrons EM, Thermal & Structural effects 2

WARP – PIC Code for Plasma Simulation Courtesy: J. -L. Vay 3

Modeling Issues for Plasma Processing RF Modeling using ACE 3 P § Calculate passband modes in cavity and determine the power on the coupler walls. § Evaluate multipacting barriers as a function of SEY, which is reduced after surface processing. Plasma simulation using WARP § Using RF field from ACE 3 P, determine onset of plasma ignition of neon gas. § Introduce oxygen plasma into the background neon plasma, study the dynamics of oxygen atoms and determine their impact density on cavity walls. 4