Cryogenic test of a proof-of-principle superconducting rf-dipole deflecting and crabbing cavity

Abstract

Recent applications in need of compact low-frequency deflecting and crabbing cavities have initiated the design and development of new superconducting structures operating at high gradients with low losses. Previously, TM 110 -type deflecting and crabbing cavities were developed and have also been operated successfully. However, these geometries are not favorable designs for low operating frequencies. The superconducting rf-dipole cavity is the first compact deflecting and crabbing geometry that has demonstrated high gradients and high shunt impedance. Since the fundamental operating mode is the lowest mode and is widely separated from the nearest higher order mode, the rf-dipole design is an attractive geometry for effective damping of the higher order modes in high current applications. A 400 MHz rf-dipole cavity was designed, fabricated, and tested as a proof-of-principle cavity. The cavity achieved high operating gradients, and the multipacting levels were easily processed and did not reoccur.

Design studies of a compact superconducting rf crab cavity for future colliders using Nb/Cu technology

“…The investigations of the RFDCC using ACE3P provide very similar results [43]. The first cold test of the RFDCC prototype revealed only the narrower barrier at the lowest field level which could successfully passed.…”

Design, prototyping, and testing of a compact superconducting double quarter wave crab cavity

“…This demands large crossing angles to alleviate the effects of beam-beam interaction. Here, an implementation of the crab-crossing technique [23][24][25][26][27][28][29] can be used to modify the angle at which bunches collide, and hence, would complement the upgraded IR quadrupole to maximize the LHC's luminosity.…”

“…This has resulted in a relatively low resonant frequency of the HL-LHC crab cavities at 400 MHz. Currently, there are three designs of compact crab cavities that are potential candidates [24][25][26][27][28][29]; the double quarter wave crab cavity (DQWCC), the subject of this article, is one of them.…”

Proton colliders at the energy frontier

“…Without countermeasures this would dramatically degrade the geometric overlap of the colliding bunches and all but eliminate any benefit from reducing the IP beam size. To avoid this degradation, the HL-LHC, the HE-LHC and FCC-hh phase 2 will all use novel crab cavities [18,19,20,21,22,23]. These are transversely deflecting RF cavities, which impart kicks of opposite sign tothe head and the tail of each bunch, so as to maintain the crossing angle of the bunch centroid motion, while at the same time restoring the full geometric bunch overlap during the collision.…”