LHC Crab Cavities: Proposed LBNL Contributions

1. LHC Crab Cavities: Proposed LBNL Contributions John Byrd LARP-CM10, BNL 23-25 Feb., 2008

2. LBNL Efforts • Design of HOM/LOM couplers (D. Li) • Extensive Microwave Studio and MAFIA modeling • Possibility of experimental verification on low power prototypes • RF Controls (J. Byrd) • Stabilized RF phase distribution (most useful for local scheme) • RF controller development • Beam-beam simulations of crabbed beams (J. Qiang) • Strong-strong code to gauge benefit of various crabbing schemes • See J. Qiang’s talk from the AP session earlier today. LARP-CM10, BNL 23-25 Feb., 2008

3. HOM/LOM Coupling • Recent progress…. • Squashed cavity • Reduced magnetic field • Degenerate mode separation • On-beam-pipe damping • Simulation and experiment shows stub coupling promising. With an optimized stub length, get Qext~200 • On-cell damping • Field enhancement acceptable • Qext low to several tens • Need to check multipacting • Multi-cell • Cell-to-cell coupling studied • 2-cell/4-cell structure • Effort highly leveraged on existing programs LARP-CM10, BNL 23-25 Feb., 2008

4. ~15 fsec Jan 2008 RF controls • Stabilized RF distribution • Uses interferometrically stabilized optical fiber to deliver ultrastable relative RF phase (<100 fsec) • Prototype tests at SLAC show stability of ~15 fsec over several weeks (<0.1 mrad@800 MHz) • RF Controller • Based on long-term development • Integral to fiber phase distribution • Work leveraged on existing development for light sources (LCLS, NSLS-II, Fermi@Elettra) LARP-CM10, BNL 23-25 Feb., 2008

5. Funding requests • Design of HOM/LOM couplers • $40k labor; $30k • RF Controls • $40k • Beam-beam simulations of crabbed beams • $10k • Travel • $10k • M&S (RF controls) • $10k • Total request: $140k LARP-CM10, BNL 23-25 Feb., 2008