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WEBEX6

WEBEX6. LHC-SKEKB800 cavity Beam Tests for LHC Yoshiyuki Morita, KEK. LHC-SKEKB800 cavity. Cell shape: almost the same as the present crab cavity two squashed cells for LHC LOM/SOM damping: coaxial couplers instead of the coaxial beam pipe HOM damping: wave guides and coaxial couplers.

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WEBEX6

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  1. WEBEX6 LHC-SKEKB800 cavityBeam Tests for LHC Yoshiyuki Morita, KEK

  2. LHC-SKEKB800 cavity • Cell shape: almost the same as the present crab cavity • two squashed cells for LHC • LOM/SOM damping: coaxial couplers • instead of the coaxial beam pipe • HOM damping: wave guides and coaxial couplers Coaxial coupler for LOM/SOM damping Waveguides for HOM damping

  3. RF parameters Frequency: 800 MHz • Compared with the baseline design; • Higher peak electric field • Lower peak magnetic field • Loss factor: 0.56 V/pC for s=3 mm (SKEKB) • Low loss factor desired for high current operation E-Peak B-Peak B-field E-field

  4. LOM/SOM/HOM • Higher LOM/SOM frequencies • Coaxial coupler insertion increases frequencies • LOM damping: Q~50 • Required for SKEKB LOM SOM

  5. Need 3D multipacting simulation KEKB prototype cavity • Present crab cavities have several multipacting levels; • In the cavity cell at 12 MV/m and 18 MV/m (not serious) • In the coaxial beam pipe at low fields (<5 MV/m, processed in one hour) • Possible multipacting sources; • Coaxial couplers • Waveguides • Irises • Simulation is the first step for making multipacting-free structure • LARP has experts for multipacting simulation B-field plot

  6. Possible multipacting sources Place where 1) High magnetic fields 2) Low electric fields Coaxial coupler Iris Waveguide B-field plot

  7. Beam tests for LHC • Beam tests for LHC crab crossing using KEKB machine • Several beam tests were proposed at the KEK-CERN video meeting (Aug. 5, 2008) • We chose controlled RF noise test • Recently Rogelio-san proposed; • Longitudinally kicked beam test with crab cavities • Observe Qs sidebands • Beam tests will be carried out on Dec. 12

  8. Proposed on Aug. 5, 2008 At the video meeting Test 1:Controlled RF noise QL=2x105 Dw=2.5kHz Can we do? Kota already tested! • Controlled RF noise • Single frequency • Close to betatron frequency, or even on top (42 kHz) • Another type: further away (50 kHz) • Measure beam size D11 station, LER or HER Frequency: 50 kHz Coordinator: K. Nakanishi LLRF: Crab cavity

  9. Test 2: Longitudinally kicked beamwith crab cavities Nov. 13, 2008 Proposed by Rogelio-san • Qs sidebands in the transverse spectrum • Akio Morita simulated a longitudinal kicked beam with crab cavities showing that some Qs sidebands might be visible in the transverse spectrum (turn-by-turn BPM) • A basic test of the beam dynamics in presence of the crab cavity D8 station Frequency: 2 kHz Coordinator: Y. Morita LLRF: ARES normal conducting cavities

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