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Odu / slac rf -dipole prototype

LHC Crab Cavity Engineering Meeting – FNAL. 13-14 December, 2012. Odu / slac rf -dipole prototype. Introduction. An overview of the ODU-SLAC cavity development and construction at 400 MHz toward a crab cavity for the LHC Cavity design and present status including

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Odu / slac rf -dipole prototype

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  1. LHC Crab Cavity Engineering Meeting – FNAL 13-14 December, 2012 Odu/slacrf-dipole prototype

  2. Introduction • An overview of the ODU-SLAC cavity development and construction at 400 MHz toward a crab cavity for the LHC • Cavity design and present status including • Deflecting mode characteristics • HOM spectra • Damping schemes • Coupler configurations and associated choices should be addressed • Cavity fabrication, treatment and recent test results

  3. Current LHC Crabbing Cavity Requirements • Local crabbing scheme frequency – 400 MHz • Requires a crabbing system at two interaction points (IP1 and IP5) • Vertical crossing at IP1 • Horizontal crossing at IP5 • Beam aperture diameter – 84 mm • Transverse dimensions ~ 145 mm • Transverse voltage – 10 MV per beam per side • Transverse voltage per cavity – 3.4 MV • Awaiting on beam tolerances based on field non-uniformity across the beam aperture <150 mm 42 mm 194 mm

  4. RF Dipole Cavity Geometry • Operates in a TE-like mode E Field H Field

  5. Characteristics of the RF-Dipole Cavity • Properties depend on a few parameters • Frequency determined by diameter of the cavity design • Bar Length ~λ/2 • Bar height and aperture determine EP and BP • Angle determines BP/EP Bar Length Cavity Length θ 84 mm

  6. 400 MHz Crabbing Cavity Designs SLAC Design ODU Design

  7. Square RF-Dipole Cavity • Square-type rf-dipole cavity to further reduce the transverse dimensions • Frequency is adjusted by curving radius of the edges • Similar to cylindrical rf-dipole design • Bar Length ~λ/2 • Bar height and aperture determine EP and BP • Angle determines BP/EP E Field H Field Height and Width < 290 mm y x

  8. HOMs and Wakefields • No lower order modes and widely separated HOMs • Separation from the fundamental crabbing mode is ~200 MHz

  9. HOM Damping Options • SLAC ACE3P Suite – Zenghai Li Waveguide Damping • Strong damping can be achieved with waveguide couplers Coaxial Coupling • Coaxial couplers requires a high pass filter to exclude the operating mode Input Coupler Three-stage high-pass filter Two-stage high-pass filter HOM Couplers & Damping, Zenghai Li

  10. Current Status on HOM Damping Waveguide Damping Coaxial Coupling Input Coupler Coupler configurations and associated choices will be presented in: HOM Couplers & Damping – Zenghai Li Two-stage high-pass filter

  11. Multipacting Analysis • Particle tracking code in the SLAC ACE3P Suite – Zenghai Li and LixinGe Modified end plates to suppress multipacting at lower fields - 0.5MV to 2.6 MV - 1.8 MV to 2.8MV - 3.0 MV to 6.0 MV

  12. Field Non-Uniformity and Multipoles (A) (B) At a transverse voltage of 1 MV Voltage deviation at 20 mm • Horizontal: 5.0%  0.2% • Vertical: 5.5%  2.4%

  13. Properties of RF-Dipole Designs Cylindrical Cavity Square Cavity

  14. Cavity Prototype Fabrication 400 MHz Prototype 499 MHz Prototype 110 220 Input Power Coupler Pick Up Probe Pick Up Probe 500

  15. Prototype Test Plan • Variable power coupler • To process multipacting • Cavity processing • Bulk BCP for 120 μm removal from the surface • High pressure rinsing • Baking for 10 hours at 6000C • Light BCP of 10 μm • In-situ baking • Cavity assembly • Fixtures to support cavity in the test cage • RF Test • Low power test while cooling down the cavity • High power test at 2 K and 4.2 K

  16. Final 400 MHz Crab Cavity Design • Goal – To design a cavity for testing at SPS and future test at LHC, meeting the design requirements • Optimize cavity geometry (ODU&SLAC) to, • Suppress multipacting levels • Revise the design to address mechanical specifications • Stress • Pressure Sensitivity • Lorentz force detuning • Achieve design rigidity with adequate stiffening • Power and HOM coupler designing • To achieve required damping requirements • Easy chemical processing of couplers • Cyomodule design • Cavity tuning and He tank designing – HyeKyoung Park (ODU/JLAB) • Cryomodule designing – Dmitry Gorelov (Niowave)

  17. Summary • The current 400 MHz rf-dipole crabbing cavity design meets current requirements on • Dimensional constraints • Electromagnetic peak surface field and transverse voltage specifications • 400 MHz rf-dipole prototype • Is in preparation for surface treatment and VTA assembly • RF testing will be performed early 2013 • Ready to continue working on designing the final cavity desgin • Currently there are several viable electromagnetic design options • The final selection will be based on the requirements on • Electromagnetic • Mechanical • Dimensional

  18. Acknowledgments • Work supported by the ODU-NiowaveP1 & P2 STTR • Work also supported by the US LHC Accelerator Research Program (LARP) through US Department of Energy contracts DE-AC02-07CH11359, DE-AC02-98CH10886, DE-AC02-05CH11231, and DE-AC02-76SF00515. • SLAC • Zenghai Li • LixinGe • Niowave • Terry Grimm • Dmitry Gorelov • ODU • Jean Delayen • Subashini De Silva • HyeKyoung Park • Julius Nfor • Alex Castilla

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