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Yuhong Zhang For ELIC and MEIC Study Groups

ELIC : A High Luminosity Ring-Ring Electron-Ion Collider at CEBAF (and Positron-Ion Collision too). Yuhong Zhang For ELIC and MEIC Study Groups International Workshop on Positrons at Jefferson Lab, March 25-27, 2009. Topics. Conceptual Design of ELIC Electron Polarization and Positron Beam

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Yuhong Zhang For ELIC and MEIC Study Groups

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  1. ELIC: A High Luminosity Ring-Ring Electron-Ion Collider at CEBAF(and Positron-Ion Collision too) Yuhong Zhang For ELIC and MEIC Study Groups International Workshop on Positrons at Jefferson Lab, March 25-27, 2009

  2. Topics • Conceptual Design of ELIC • Electron Polarization and Positron Beam • Low to Medium Energy Collider and Staging of ELIC

  3. Science Motivation A High Luminosity, High Energy Electron-Ion Collider: A New Experimental Quest to Study the Glue which Binds Us All How do we understand the visible matter in our universe in terms of the fundamental quarks and gluons of QCD? Explore the new QCD frontier: strong color fields in nuclei • How do the gluons contribute to the structure of the nucleus? • What are the properties of high density gluon matter? • How do fast quarks or gluons interact as they traverse nuclear matter? Precisely image the sea-quarks and gluons in the nucleon • How do the gluons & sea-quarks contribute to the spin structure of the nucleon? • What is the spatial distribution of the gluons and sea quarks in the nucleon? • How do hadronic final-states form in QCD?

  4. ELIC Design Goals • Energy • Center-of-mass energy between 20 GeV and 90 GeV • energy asymmetry of ~ 10,  3 GeV electron on 30 GeV proton/15 GeV/n ion up to 10 GeV electron on 250 GeV proton/100 GeV/n ion • Luminosity • 1033 up to 1035 cm-2 s-1per interaction point • Ion Species • Polarized H, D, 3He, possibly Li • Up to heavy ion A = 208, all striped • Polarization • Longitudinal polarization at the IP for both beams • Transverse polarization of ions • Spin-flip of both beams • All polarizations >70% desirable • Positron Beamdesirable

  5. Green-field design of ion complex directly aimed at full exploitation of science program. ELIC Conceptual Design Accumulator-cooler ring & prebooster 30-250 GeV protons 15-100 GeV/n ions 3-10 GeV electrons 3-10 GeV positrons 12 GeV CEBAF Upgrade

  6. Figure-8 Ring Footprint 20000 z [cm] 10000 180 m 430 m 90 deg x [cm] 0 -40000 -30000 -20000 -10000 0 10000 20000 30000 40000 -10000 -20000 Interaction Point electron ring Ion ring Vertical crossing Figure-8 Ring Stacked vertically • Design is determined by • Synchrotron radiation power • Arc bending magnet strength • Length of crossing straights • Cost and fit to site

  7. ELIC Baseline Design Choice • Energy Recovery Linac-Storage-Ring (ERL-R) • ERL with Circulator Ring – Storage Ring (CR-R) • Back to Ring-Ring (R-R) – by taking CEBAF advantage as full energy polarized injector • Challenge: high current polarized electron (positron) source • ERL-Ring: 2.5 A • Circulator ring: 20 mA • State-of-art: 0.1 mA • 12 GeV CEBAF Upgrade polarized source/injector already meets beam requirement of ring-ring design • CEBAF-based R-R design still preserves high luminosity, high polarization (+polarized positrons…)

  8. Achieving High Luminosity of ELIC ELIC design luminosity L~ 7.8 x 1034 cm-2 sec-2 (150 GeV protons x 7 GeV electrons) ELIC luminosity Concepts • High bunch collision frequency (up to 1.5 GHz) • Short ion bunches (σz ~ 5 mm) • Super strong final focusing (β* ~ 5 mm) • Large beam-beam parameters (0.01/0.086 per IP, 0.025/0.1 largest achieved) • Need High energy electron cooling of ion beams • Need crab crossing colliding beams • Large synchrotron tunes to suppress synch-betatron resonances • Equal betatron phase advance (fractional) between IPs

  9. ELIC New Nominal Parameters • These parameters are derived assuming a 6 m detector space, 27 mrad crab crossing angle, 10 to 14 sigma radius for aperture, 10 kW/m synchrotron radiation power density limit

  10. ELIC (e/A) Design Parameters * Luminosity is given per unclean per IP

  11. ELIC Ring-Ring Design Features • Unprecedented high luminosity • Enabled by short ion bunches, low β*, high rep. rate, large synchrotron tune • Require crab crossing colliding beam • Electron cooling is an essential part of ELIC • Four IPs (detectors) for high science productivity • “Figure-8” ion and lepton storage rings • Ensure spin preservation and ease of spin manipulation • No spin sensitivity to energy for all species. • Present CEBAF gun/injector meets electron storage-ring requirements • The 12 GeV CEBAF can serve as a full energy injector to electron ring • Simultaneous operation of collider and CEBAF fixed target program. • Experiments with polarized positron beam are possible.

  12. spin rotator spin rotator spin rotator with 90º solenoid snake collision point collision point collision point collision point spin rotator with 90º solenoid snake spin rotator spin rotator Electron Polarization in ELIC • Producing at source • Polarized electron source of CEBAF • Preserved in acceleration at recirculated CEBAF Linac • Injected into Figure-8 ring with vertical polarization • Maintaining in the ring • High polarization in the ring by electron self-polarization • SC solenoids at IRs removes spin resonances & energy sensitivity.

  13. Matching at IP • vertical in arc, longitudinal at IP • Vertical crossing bend causing energy-dependent spin rotation • Spin rotators with vertical crossing bends of IP Electron Polarization in ELIC(cont.) Solenoid spin rotator Vertical bending dipole Vertical bending dipole Solenoid spin rotator spin e Spin tune solenoid spin tune solenoid e collision point collision point i i Arc bending dipoles Arc bending dipoles spin tune solenoid spin tune solenoid 90º 90º • Polarization lifetime • Depolarization can reduce polarization • (eg. spin flip, Sokolov-Ternov effect becomes depolarization) • Replacement of electron/positron bunches as needed. Vertical bending dipole Vertical bending dipole Spin rotators

  14. converter 10 MeV e+ e+ 5 MeV Transverse emittance filter Longitudinal emittance filter e e - - Polarized source 15 MeV e e - - e e - - e e - e - - e+ e+ e+ e+ dipole dipole 115 MeV dipole Unpolarized source e e - - During positron production: - Polarized source is off - Dipoles are turned on 15 MeV Positrons in CEBAF/ELIC • Non-polarized positron bunches generated from modified electron injector through a converter • Polarization realized through self-polarization at ring arcs (B. Wojtsekhowski)

  15. Self-Polarization in ELIC(cont.) Electron/positron polarization parameters * Time can be shortened using high field wigglers. ** Ideal max equilibrium polarization is 92.4%. Degradation is due to radiation in spin rotators.

  16. Low to Medium Electron-Ion Collider and Staging of ELIC: Motivations A medium energy EIC becomes the low energy ELIC ion complex Science Lower energies and symmetric kinematics provide new science • Valence quarks/gluon structure beyond JLab 12 GeV • Asymmetric sea for x ~ M / MN • GPDs, transverse spin at x ~ 0.1 Accelerator Advantages/Benefits • Bring ion beams & associated technologies to JLab • Have an early ring-ring collider at JLab • Provides a test bed for new technologies required by ELIC • Develop expertise and experience, acquire/train technical staff

  17. MEIC & Staging of ELIC

  18. Medium Energy EIC Features • High luminosity collider L~ 2×1033 cm-2s-1 (9 GeV protons x 9 GeV electrons) • CM energy region from 10 GeV (5x5 GeV) to 22 GeV (11x11 GeV), and possibly reaching 35 GeV (30x10 GeV) • High polarization for both electron and light ion beams • Natural staging path to high energy ELIC • Possibility of positron-ion collider in the low to medium energy region • Possibility of electron-electron collider (7x7 GeV) using just small 300 m booster/collider ring

  19. MEIC Parameter Table

  20. Key R&D Issues • Forming low energy ion beam and space charge effect • Cooling of ion beams • Beam-beam effect • Dynamics of crab crossing beams and crab cavity development • Traveling focusing scheme for MEIC

  21. Summary • The ELIC collider promises to accelerate a wide variety of polarized light ions and un-polarized heavy ions to high energy, to collider with polarized electron or positron beam enabling a unique physics program • The final ELIC luminosity should comfortable exceed 1x1034 cm-2s-1 for electron(positron)-proton collisions • Low/medium energy collider (MEIC) enables rich physics program not covered by high-energy collider. The initial design studies indicated that luminosity can exceed 1x1033 cm-2s-1 . Conceptual design iteration is still in progress. • Positron beam can also be used for additional positron-ion and electron-positron collision programs. Both electron and positron beam possess high (>80%) polarization. ELIC is the primary future goal of Jlab!

  22. ELIC Study Group A. Afanasev, A. Bogacz, J. Benesch, P. Brindza, A. Bruell, L. Cardman, Y. Chao, S. Chattopadhyay, E. Chudakov, P. Degtiarenko, J. Delayen, Ya. Derbenev, R. Ent, P. Evtushenko, A. Freyberger, D. Gaskell, J. Grames, L. Harwood, A. Hutton, R. Kazimi, G. A. Krafft, R. Li, L. Merminga, J. Musson, M. Poelker, R. Rimmer, C. Tengsirivattana, A. Thomas, H. Wang, C. Weiss, B. Wojtsekhowski, B. Yunn, Y. Zhang - Jefferson Laboratory W. Fischer, C. Montag - Brookhaven National Laboratory V. Danilov - Oak Ridge National Laboratory V. Dudnikov - Brookhaven Technology Group P. Ostroumov - Argonne National Laboratory V. Derenchuk - Indiana University Cyclotron Facility A. Belov - Institute of Nuclear Research, Moscow, Russia V. Shemelin - Cornell University MEIC Study Group S. Bogacz, Ya. Derbenev, R. Ent, G. Krafft, T. Horn, C. Hyde, A. Hutton, F. Klein, P. Nadel-Turonski , A. Thomas, C. Weiss, Y. Zhang

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