LARP-CM10, BNL 23-25 Feb., 2008LARP-CM10, BNL 23-25 Feb., 2008 J. Byrd, Lawrence Berkeley National LaboratoryJ. Byrd, Lawrence Berkeley National Laboratory

LHC Crab Cavities: Proposed LBNL Contributions

John Byrd

LARP-CM10, BNL 23-25 Feb., 2008LARP-CM10, BNL 23-25 Feb., 2008 J. Byrd, Lawrence Berkeley National LaboratoryJ. Byrd, Lawrence Berkeley National Laboratory

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., 2008LARP-CM10, BNL 23-25 Feb., 2008 J. Byrd, Lawrence Berkeley National LaboratoryJ. Byrd, Lawrence Berkeley National Laboratory

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., 2008LARP-CM10, BNL 23-25 Feb., 2008 J. Byrd, Lawrence Berkeley National LaboratoryJ. Byrd, Lawrence Berkeley National Laboratory

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)

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LARP-CM10, BNL 23-25 Feb., 2008LARP-CM10, BNL 23-25 Feb., 2008 J. Byrd, Lawrence Berkeley National LaboratoryJ. Byrd, Lawrence Berkeley National Laboratory

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