DOE OSTI2012
The design and construction of electron-ion colliders, EIC, will be facilitated by the development of an SRF “crab crossing” cavity with 0.5 to 1.5 GHz frequency and 20 to 50 MV of total integrated voltage. The development of RF cavities that provide a transverse kick to the particle beam will include RF design, computer modeling, and hardware development. Current state of the art crab cavities provide 2- 5 MV of integrated voltage, and most of the existing designs require complex schemes to damp unwanted RF modes. We propose a novel design for TEM-like, room-temperature, two-bar structures, or hybrid structures with one resonant bar and one input coax per module, which can also be implemented for SRF conditions. Unwanted modes are coupled out of the cavity by the coax input line, and this provides a uniquely simple method to reduce the strength of higher-order modes. Critical phase stability for the crabbing voltage is provided by the low-level RF system, which controls the RF to the input ports of the novel crab cavity design. Designs for a series of cavities, or for multiple-module cavities, will provide the 20-50 MV of integrated voltage in an electron-ion collider, while meeting the critical thermal and mechanical requirements for heat loads, alignment, and phase stability. RF designs for various module alternatives were evaluated in Phase I. A single module of a hybrid design with one resonant bar and one coax input was built for room-temperature, low-power testing with a bead-pull measurement. Several additional designs were explored that made use of a high RT/Q, voltage-efficient, S-mode structure.