Microwave instability threshold from coherent wiggler radiation impedance in storage rings

The contribution of coherent wiggler radiation (CWR) to the microwave instability threshold in wiggler-dominated storage rings such as damping for colliders is discussed detail. Three different impedance models are considered: free-space steady-state model, parallel-plates shielding and rectangular-chamber model. field dynamics CWR compared, showing that broad-band unshielded becomes dominated by resonant structures when chamber considered. To suppress narrow-band wigglers with shielding, we propose employing a detuned wiggler. A new, simple, analytical method solving dispersion relation detecting CWR-driven presented. theory compared numerical simulations Vlasov-Fokker-Planck solver Electron Ion Collider backup ring cooler confirms gets higher negative momentum compaction.