The Next Linear Collider damping ring RF system

We report progress on the design of the RF systems for the Next Linear Collider (NLC) damping rings. The 714 MHz RF system is a critical component of the damping ring complex, and must provide flexible operation with high-power systems generating 1.5 MV in the main damping rings and 2 MV in the positron pre-damping ring. Average beam currents are approximately 750 mA, and bunch trains are rapidly injected and extracted. A cavity design incorporating higher-order-mode (HOM) damping schemes to minimize beam impedance and maximize current thresholds for coupled-bunch instabilities will be presented. Cavity construction techniques are designed to reduce costs while providing a reliable system with excellent performance. Descriptions of feedback systems requirements will be presented, with particular attention to the klystron bandwidth requirement for feedback against transient beam loading. Flexible low-level controls and feedback loops will be described.