Design of Dressed Crab Cavities for the HL-LHC Upgrade

The HL-LHC upgrade relies on a set of RF crab cavities for reaching its goals. Two parallel concepts, the Double Quarter Wave (DQW) and the RF Dipole (RFD), are going through a comprehensive design process along with preparation of fabrication in view of extensive tests with beam in SPS. High Order Modes (HOM) couplers are critical in providing damping in RF cavities for operation in accelerators. HOM prototyping and fabrication have recently started at CERN. In this paper, an overview of the final geometry is provided along with an insight in the mechanical and thermal analyses performed to validate the design of this critical component. Emphasis is also given to material selection, prototyping, initial fabrication and test campaigns that are aimed at fulfilling the highly demanding tolerances of the couplers.