Initiating the Crab System R&D Graeme Burt Lancaster University Philippe Goudket Daresbury Laboratory

Crab Cavity Team Graeme Burt RA Lancaster Uni. Amos Dexter SL Lancaster Uni. Philippe Goudket RF Eng. Daresbury Alexander Kalinin RF Eng. Daresbury Carl Beard RF Eng. Daresbury Mike Dykes RF Group LeaderDaresbury Mike Poole (Work Package 5 Leader)

Crab Cavity work plan 2005 Analysis of requirement. Interact with international community on specification of crab cavity solution. Design experiment to investigate phase control limitations. Design of cavity for phase control experiment. Crab Cavity longer term work plan Build and operate phase control system experiment. Design experiment to test crab cavity phase control systems on test beam. Beam testing of cavities and control system.

Finite crossing angles The luminosity of a collision is reduced by a finite crossing angle. The beams are rotated for a effective head-on collision, by a crab cavity. Crab cavity Crab cavity Tilted bunch Effective head-on collision finite crossing angle

Transverse deflecting dipole mode The dipole mode of an elliptical cavity can be used to transversely deflect the beam. Magnetic field lines of the dipole mode. Beam into page through centre point Field is uniform in the beam direction Sinusoidal in time

KEK-B Crab Cavity Crab Cavities are currently under test at the KEK-B B factory, these have less stringent phase stability and lower kicks required.

Transverse deflecting dipole mode Magnetic Field as seen by front, middle, and back of the bunch as a function of position across the cavity. (At any instant the magnetic field is uniform across the cavity)

Crab cavity operation B = max field in crab cavity d = distance from cavity to interaction point field jitter between cavities gives differing bunch rotation For optimum cell length

Transverse deflecting dipole mode Magnetic Field as seen by front, middle, and back of the bunch as a function of position across the cavity for phase error.

Momentum mismatch Δx Differential phase jitter causes the two bunches to have a height mismatch, which can significantly reduce luminosity or cause the bunches to miss. t o = time bunch enters cavity d = distance to IP t o = 0 t o ≠ 0

Issues Position of crab cavities Type of crab cavity Frequency of operation How phase jitter affects luminosity? How field stability affects luminosity? Effect of wakefields i.e. cavity harmonics Performance of phase control systems

Crab cavity phase control system Fast phase adjust using a second klystron and fast phase difference. Diagram by J. Frisch

Crab cavity Phase stabilization Test System Diagram by J. Frisch