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CASA Collider Design Review Retreat HERA The Only Lepton-Hadron Collider Ever Been Built Worldwide

CASA Collider Design Review Retreat HERA The Only Lepton-Hadron Collider Ever Been Built Worldwide. Yuhong Zhang February 24, 2010. Outline. Overview, baseline design and parameters Polarization and cooling Luminosity upgrade Interaction region. e-p. electron on polarized gas target.

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CASA Collider Design Review Retreat HERA The Only Lepton-Hadron Collider Ever Been Built Worldwide

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  1. CASA Collider Design Review RetreatHERAThe Only Lepton-Hadron Collider Ever Been Built Worldwide Yuhong Zhang February 24, 2010

  2. Outline • Overview, baseline design and parameters • Polarization and cooling • Luminosity upgrade • Interaction region

  3. e-p electron on polarized gas target Proton on wire target e-p • Construction started in April 1984, ended on Dec. 1990 • Commissioning took place in 1991 (First collision on Oct. 14, 1991) • Data taken in June. 1992

  4. HERA Collider Rings • Design requirements • head-on collisions • Energy range • p: up to 300 to 820(920) GeV (lower limit by maximum path length adjustment for preserving e and p synchronism) • e: up to 30 GeV • RF power (SR loss) limit 7.2 MW

  5. HERA Collider Rings Arc • Ring circumference: 6336 m • (determined by maximum p energy) • Four quadrants: north, east, south, west • Quadrant = two mirror symmetric octants • Each octant has 18 FODO cells • Ion FODO: 47 m, phase advance 60° • 416 SC dipoles (4.6 K), 8.83 m, 4.68 T, radius 584m, 75 mm aperture • 6 vertical dipoles, 3.356 m • 224 SC quads, 1.5 to 1.86 m, 90 T/m • e FODO: 23.5 m, phase advance 60° • half of ion FODO cell length Straights • Four 360 m straights for four IRs • Straights also for injection/ejection, RF, beam dump, collimators, etc • Electron straight also includes spin rotators (interleafed vertical & horizontal bending magnets) • Small electron betatron functions (strong focusing) in RF sections for reducing bad orbit-RF coupling (eg. single and multiple bunch instabilities) • Minimizing dispersion in RF sections for avoiding synchro-betatron resonances

  6. HERA Injectors • Electron/positron (polarized) • An S-band warm linac  450 MeV pulsed current • Accumulator ring PIA (also bunching) into single bunch • Synchrotron DESY II  7 GeV • e-P storage ring PETRA  12 GeV, filling with 60 bunches • HERA collider ring  27.5 GeV • Self-polarization • Proton/ions • An H- sources, a 750 KeV RFQ • A 50 MeV H- linac • Synchrotron DESY III  7.5 GeV (transition energy is 9 GeV) • Striping at injection of DESY III • e-P storage ring PEREA  40 GeV (transition energy is 6.5 GeV) • HERA collider ring  920 GeV

  7. Synchrotron DESY II and III • Proton emittance determined by space charge effect in proton injector • Beam spot size (and luminosity) at IP is determined by • Beam emittance • Chromaticity & dynamical aperture  smallest acceptable β* at IP

  8. HERA Design Parameters

  9. Polarized Lepton Beams

  10. (Unrealized) Electron Cooling 120 m • Continuous cooling • Cooling bunch dimensions can be smaller than ion bunch • Wiggler with 1 T • A high-β (~500 to 2000) insertion

  11. e Ring Lattice & chromaticity Correction • Change of FODO cell betatron phase advance • Increasing focusing in FODO lattice reduces electron beam equilibrium emittance, reaching minimum at 135° phase advance per cell • Strong focusing (large betatron phase advance per FODO cell) causes big chromaticity • Needs strong sextupole strengths to correct chromaticity, but reduces dynamical apertures  a compromise: 90° for horzontal and 75° for vertical  equilibrium emittance for 27.5 GeV is 22 nm (In the north, south and east straight sections, high dispersion caused by bends in spin rotators contribute significantly to the emittances) • Interleaved Chromaticity correction scheme • Two families in the horizontal plane, three families in the vertical plane • Chromatic correction adequate but worse in the horizontal plane • Non-interleaved chromaticity correction scheme • Requires stronger sextupole strength

  12. Electron Dynamics Study for Luminosity Upgrade • Goal: reducing beam emittance through • Change of RF frequency • Increase focusing (phase advance) • Dynamics aperture study (G. Hoffstatter)

  13. Synchrotron Radiation • No upstream collimators • Radiation fan must pass through IR • Main background sources: back-scattering from absorbers 11 to 27 m right of IP • Small central beam pipe • Total power 18 kW (26 kW at 30 GeV) • Critical energy up to 115 keV (150 at 30 GeV) • Detector shielded by 3 movable upstream collimators • Two fixed collimators near IP against back scattering • Background conditions very low

  14. Special Magnets

  15. Things Still Bother Them at Last Days of HERA 2007

  16. End of a Great Machine & Era

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