Abstract
CERN’s compact linear collider CLIC requires crab cavities on opposing linacs to rotate bunches of particles into alignment at the interaction point (IP). These cavities are located approximately 25 metres either side of the IP. The luminosity target requires synchronisation of their RF phases to better than 5 fs r.m.s. This is to be achieved by powering both cavities from one high power RF source, splitting the power and delivering it along two waveguide paths that are controlled to be identical in length to within a micrometre. The waveguide will be operated as an interferometer. A high power phase shifter for adjusting path lengths has been successfully developed and operated in an interferometer. The synchronisation target has been achieved in a low power prototype system.
Highlights
Designs for CERN’s compact linear collider CLIC [1] have electrons and positrons colliding with centre of mass energies between 280 GeV and 3 TeV
The slender profile of the bunches at the interaction point (IP) means that if they retain their crossing angle at the IP luminosity will be reduced to just 10% of what could be obtained when the bunches are sheared into alignment with a z dependent transverse displacement
A scheme for synchronising the CLIC crab cavities has been set out requiring the operation of a waveguide interferometer at 12 GHz
Summary
Designs for CERN’s compact linear collider CLIC [1] have electrons and positrons colliding with centre of mass energies between 280 GeV and 3 TeV. The slender profile of the bunches at the interaction point (IP) means that if they retain their crossing angle at the IP luminosity will be reduced to just 10% of what could be obtained when the bunches are sheared into alignment with a z dependent transverse displacement. If the phase of a crab cavity is not exactly 90◦ from the phase of maximum possible deflection the bunch receives a shear (or pseudo rotation) about a point that is not its geometrical centre resulting in an average deflection at the IP. This paper proposes the operation of an interferometer inside the high power waveguide that distributes power to the crab cavities. This allows accurate synchronisation to be maintained.
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