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Experience with Crab cavities

Experience with Crab cavities. The 4th Electron Ion Collider Workshop 19-23 May, 2008 Hampton University Mika Masuzawa, KEK. Contents. Introduction Where/What is KEKB? Characteristics of KEKB Machine performance before Crab cavities Luminosity history Machine parameters

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Experience with Crab cavities

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  1. Experience with Crab cavities The 4th Electron Ion Collider Workshop 19-23 May, 2008 Hampton University Mika Masuzawa, KEK The 4th EIC workshop May 19-23, 2008

  2. Contents • Introduction • Where/What is KEKB? • Characteristics of KEKB • Machine performance before Crab cavities • Luminosity history • Machine parameters • Machine performance with Crab cavities • Crab crossing scheme • Cavity production & installation • Beam commissioning with crab cavities • Can we confirm the prediction? • Summary The 4th EIC workshop May 19-23, 2008

  3. 1. Introduction Where/What is KEKB? Characteristics of KEKB The 4th EIC workshop May 19-23, 2008

  4. Mt. Tsukuba Nikko Where KEKB tunnel ~11 m below Ground Level Belle @IP Tokyo Mt.Fuji Linac Aerial view of KEK About KEKB

  5. Superconducting cavities (HER) IR Belle detector e- KEKB B-Factory e+ ARES cavities (HER) ARES cavities (LER) 8 GeV e- 3.5 GeV e+ Linac e+ target What is KEKB • Beam energy • 8GeV (electron, “HER”) • 3.5GeV (positron, “ LER”) • Circumference • 3016 m • Uses TRISTAN tunnel • RF system • fRF ~ 509MHz • ARES (LER) • ARES+SCC (HER) The construction of KEKB began in 1994, and was completed in November 1998. Commissioning started in Dec.1998. The 4th EIC workshop May 19-23, 2008 About KEKB

  6. Characteristics of KEKB The 4th EIC workshop May 19-23, 2008

  7. Finite crossing angle Superconducting Q magnet for final focus. Small beam size achieved at IP Superconducting Cavities Storage of high current >1.4 A IR Solenoids on vacuum pipe SCC Solenoids to reduce electron cloud effects Arc section magnets Characteristics of KEKB ARES J-LINAC: Efficient acceleration in a limited space Two bunch positron injection ARES normal conducting cavities: Large storage cavity for stable acceleration 2.5p Cell Lattice: Low non-linearity high flexibility Bunch-by-bunch feedback system The 4th EIC workshop May 19-23, 2008

  8. Interaction Region • Vertical focusing by a pair of superconducting Q-magnets （QCSL/QCSR）. • Extra vertical focusing by QC1L/R for the electron beam. • One beam must go off axis due to the finite crossing angle at the IP. • To minimize the flux of SR through the IP, the incoming positron (electron) beam orbit is set on the axis of QCSL (QCSR). • Superconducting solenoid magnets SL/R used for compensating the detector solenoid field. The 4th EIC workshop May 19-23, 2008 Characteristics of KEKB

  9. More on Interaction Region • KEKB has 22 mrad horizontal crossing angle at the IP: • Easier beam separation • Simpler design around the IP. • Fewer components. • Less synchrotron radiation. • Less luminosity-dependent background. • Space for compensation solenoid, etc. KEKB PEP-II Characteristics of KEKB

  10. Machine performance before Crab cavities Luminosity history Peak luminosity Integrated luminosity Machine parameters (Design & Best) The 4th EIC workshop May 19-23, 2008

  11. Luminosity history Peak design Daily The 4th EIC workshop May 19-23, 2008

  12. Peak luminosity The 4th EIC workshop May 19-23, 2008

  13. Highest luminosity ever achieved by a collider The 4th EIC workshop May 19-23, 2008

  14. 1034 1033 1032 1031 1030 1029 Peak luminosity (cm-2 s -1) 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year The 4th EIC workshop May 19-23, 2008

  15. Integrated luminosity The 4th EIC workshop May 19-23, 2008

  16. The best day (1.23 /fb/day) before Crab cavity installation Design luminosity The 4th EIC workshop May 19-23, 2008

  17. Continuous injection scheme since 2004 The 4th EIC workshop May 19-23, 2008

  18. Integrated luminosity The 4th EIC workshop May 19-23, 2008

  19. Machine parameters The 4th EIC workshop May 19-23, 2008

  20. Machine parameters (Best & Design) The 4th EIC workshop May 19-23, 2008

  21. More on the machine parameters of Nov.15, 2006 The 4th EIC workshop May 19-23, 2008

  22. Machine performance Summarybefore Feb. 2007 (without crab cavities) • Recorded highest luminosity of 17 /nb/sec (1.7x1034 /cm2/s), with a crossing angle at the IP. The 4th EIC workshop May 19-23, 2008

  23. For even higher luminosity • Achieve a head-on collision while keeping the crossing angle at the IP. • Crab Crossing Scheme The 4th EIC workshop May 19-23, 2008

  24. Machine performance with Crab cavities What is Crab crossing scheme? Cavity production and installation Beam commissioning The 4th EIC workshop May 19-23, 2008

  25. What is Crab crossing scheme? The 4th EIC workshop May 19-23, 2008

  26. Input Coupler Liq. Helium Vessel SUS Support Pipe Stub Support Notch Filter Coaxial Coupler RF Absorber 80 K Liq. Nitrogen Shield Copper Bellows Aluminum End Plate Aluminum End Plate Crab Crossing Scheme Need two RF deflectors for each ring First proposed by R. B. Palmer in 1988 for linear colliders. K. Hosoyama, et al. Simulation by K. Ohmi Head-on (crab) (Strong-strong simulation) Crossing angle 22 mrad

  27. Crab crossing scheme (our choice) Install one crab cavity per ring, at Nikko straight section where superconducting acceleration cavities (SCC)are located. • Saves on cost of cavities and cryogenic systems. • Avoids synchrotron radiation hitting the cavity. The 4th EIC workshop May 19-23, 2008

  28. Crab crossing scheme Comparison between two cavities/ring and one cavity/ring bunch head bunch tail IP IP crab cavity crab cavity crab cavity 2 cavities per ring 1 cavity per ring beam beam orbits of bunchheadandtail Different COD between head and tail Same COD The 4th EIC workshop May 19-23, 2008

  29. Crab Crossing Scheme (KEKB) • Beam tilts all around the ring. • z-dependent horizontal closed orbit. • tilt at the IP (head on): Crab cavities Streak cameras to observe the tilt Tilt angle depends on crab voltage, bx *and bx(Crab). Typical parameters for Crab crossing The 4th EIC workshop May 19-23, 2008

  30. What crab cavity looks like The 4th EIC workshop May 19-23, 2008

  31. K. Hosoyama et al Crab Cavity & Coaxial Coupler in Cryomodule Support rod Jacket type main He vessel(SUS316L) RF absorber (Ferrite) Jacket type sub He vessel Support pipe tuning rod Input coupler Notch filter Crab cavity cell RF absorber (Ferrite) Coaxial beam pipe (Nb) Extract TM010, TE111 mode frequency tuning Stub support Bellows

  32. Schematic Drawing of Cryostat The 4th EIC workshop May 19-23, 2008

  33. Cavity production and installation The 4th EIC workshop May 19-23, 2008

  34. Crab Cavity Fabrication Procedure Crab Cavity Cell Beam Pipe & Flange Tokyo Denkai 5 mm t RRR = 180 MHI Kobe Nb Sheet Nb Sheet Half Cell Hydro-forming Rolle Mechanical Polishing & Trimming Electron Beam Welding Grinding of Welding Part Cell Equator KEK Tsukuba EP 2 ~ 5 mm Barrel Polishing ~ 100 mm Electro-Polishing EP 1 ~ 100 mm Electro-Polishing High Pressure Water Rinsing Nomura Plating Kanuma 80 bar. 60 min. High Pressure Water Rinsing Assembling for Cold Test Kinzoku Giken Mito Annealing 700 oC x 3 hr Cold Test in Vertical Cryo.

  35. Forming and barrel polishing Barrel Polishing Nov. 11, 2005 at KEK Polishing Time 312 hours Forming of 4 Half-Cells for Crab Cavity for LER and HER Feb. 14, 2005 at Mitsubishi Heavy Industries, LTD. Kobe

  36. High Pressure Rinsing and Assembling for RF Cold Test Set flanges of beam pipes and ports in Class 100 clean room Nozzle High pressure water rinsing by 80 bar Ultra-Pure water Rotation & up-down motion

  37. Electro Polishing & Annealing Crab Cavity: Rotating ~ 1 rpm Cathode: Aluminum Straight Pipe Electro Polishing at Nomura Plating Ltd. Titanium Box EP 1 ~ 100 μm EP 2 ~ 5 μm Annealing at 700oC for 3 hours at Kinzoku Giken Ltd.

  38. Alignment of coaxial coupler Determine the axis of the coaxial coupler set in the cryostat by using transit. Align the axis of the coaxial coupler which will be connected to the coaxial coupler on cryostat side.

  39. Move to Test Stand for Cool-down & High Power Test April 26, 2006 1st Oct. 16, 2006 2nd Mt. Tsukuba Crab cavity for HER Dec. 6, 2006 Crab cavity for LER

  40. Q0 vs. Esp Curve These figures show the comparison of Q0 vs. Esp curve between Vertical and Horizontal Test for the both Crab Cavities. LER Crab Cavity HER Crab Cavity shows the target value in the operation.

  41. Two crab cavities were installed in KEKB in January 2007. HER (e-, 8 GeV) LER (e+, 3.5 GeV) The 4th EIC workshop May 19-23, 2008

  42. Beam commissioning with crab cavities Be very careful as we have no spare cavities Will the beam receive the kick that we want? Can we collide the crabbed beams? No extra heating due to crabbing in the entire ring? The 4th EIC workshop May 19-23, 2008

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