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Design and Requirements for Global and Local Crab Cavity Schemes

Explore the design considerations and requirements for both global and local crab cavity schemes, including cavity parameters, cryostat design, coupler orientation, and environmental limitations.

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Design and Requirements for Global and Local Crab Cavity Schemes

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  1. LARP CM14 Collaboration Meeting April 27, 2010Fermilab CAVITY/COUPLER, MULTIPACTING AND CRYOSTAT THOUGHTS V. Yakovlev, N. Solyak and I. Gonin Fermi National Accelerator Laboratory CM14, FNAL, Apr.27, 2010

  2. Before LHC-CC09, 3rd LHC Crab Cavity Workshop (CERN, Sept.16-18, 2009) a global CC scheme was considered: Cavity location (only one cavity for proof-of-principle demonstration ) CM14, FNAL, Apr.27, 2010

  3. Crab cavity for the Global scheme • Crab cavity (CC) parameters for the global scheme were determined (transverse kick, operating frequency, input power, etc); • Requirements for the CC transverse and longitudinal HOM impedances and quality factors, transverse dimensions were formulated; • Crab cavity concept design was developed (SLAC); • Environment limitations were in process of investigated and formulated; • Requirements for CC cryogenic system were formulated basing on what is available in the tunnel; • Requirements to the coupler orientation and position were formulated; • Requirements to the CM were clarified; • The concept design of the CM was performed. CM14, FNAL, Apr.27, 2010

  4. Three Crab Cavity designs for a global scheme SLAC design with coaxial couplers UK design with WG couplers KEK design with coax and WG couplers CM14, FNAL, Apr.27, 2010

  5. Cryostat (concept design) Schematic of the LHC Crab Cavity cryostat. The outer diameter (900 mm) is constrained by the limited space between Helium vessel and cryogenic line. The length is 1150mm. CM14, FNAL, Apr.27, 2010

  6. However, during the 3rd LHC Crab Cavity Workshop ( CERN, September, 16-18, 2009) a local CC scheme was chosen: Local LHC crab crossing scenario. Two crab structures are shown on the side of interaction point to crab and anti-crab the beam in the IR region. Schematic of the crab crossing scheme for the Phase II upgrade of the LHC. CM14, FNAL, Apr.27, 2010

  7. Crab Cavity in Local scheme • The local scheme demands redesign of the optics in the interaction point region • A new approach to the existing IR upgrade optics by using additional D11 & D12 dipoles allows separate the two beam lines to ~27 cm for inserting crab cavities; • The crab cavity should provide the transverse kick of up to 5 MV • The cavity aperture is limited by 120-140 mm; • In order to prevent CBM instability, the Q-factor of lower monopole modes is to be lower than 200, and shunt impedance should not exceed 137 kΩ; • Requirements for transverse impedance are to be reconsidered, because beta-functions in the CC positions are different for global and local schemes. CM14, FNAL, Apr.27, 2010

  8. Crab Cavity in Local scheme • For the local CC scheme we should repeat all the steps we did for the global one: • Investigation of the environment limitations; • Formulation requirements for CC cryogenic system in order to fit it to the Helium system available in the tunnel; • Requirements to the couplers and tuners should be developed (orientation and position); • Requirements to the CM is to be clarified; • The concept design of the CM is to be performed. CM14, FNAL, Apr.27, 2010

  9. 1 3 2 Multipacting analysis • To start multipactoring investigations, we need: • Realistic cavity design taking into account beam physics requirements and environmental constrains; • Realistic coupler design. CST Particle Studio defined 3 areas with MP activity in KEK Crab cavity (positive growth rate) 1 inlong part of racetrack; 2 in coaxial line; 3 In place of connection of coaxial to the cavity wall Example: CM14, FNAL, Apr.27, 2010

  10. Summary In order to start the Cryostat design we need the following: • The environment requirements for the local scheme CC should be revised and formulated; • The details of the cryostat position and distances to the critical elements of the environment are to be clarified; • More detailed cavity package design is required: • Specification (cooling, tuning, forces, etc…) and mechanical/alignment tolerances • Real design of the couplers (FPC and HOM) - cooling, supports, assembly. CM14, FNAL, Apr.27, 2010

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