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RHIC Accelerator Capability: Present and Future

RHIC Accelerator Capability: Present and Future. Mei Bai Collider Accelerator Dept. BNL. Outline. Achieved performance Polarization and Luminosity Future Plans Improve polarized proton performance Explore options for Drell-Yan experiment Parasitic to colliding mode

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RHIC Accelerator Capability: Present and Future

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  1. RHIC Accelerator Capability: Present and Future Mei Bai Collider Accelerator Dept. BNL

  2. Outline • Achieved performance • Polarization and Luminosity • Future Plans • Improve polarized proton performance • Explore options for Drell-Yan experiment • Parasitic to colliding mode • Internal fixed target(see W. Fischer’s presentation) • External fixed target(see K. Brown’s presentation) • Explore the energy limit • Investigating acceleration of other polarized light ion beams • He3, Deuteron, Tritium, …

  3. BRAHMS(p) Absolute Polarimeter (H jet) RHIC pC Polarimeters Siberian Snakes Spin flipper PHENIX (p) STAR (p) Spin Rotators (longitudinal polarization) Spin Rotators (longitudinal polarization) Solenoid Partial Siberian Snake LINAC BOOSTER Helical Partial Siberian Snake Pol. H- Source AGS 200 MeV Polarimeter AGS Polarimeters Strong AGS Snake SpinFest, August 7, 2008

  4. Summary of Achieved Performance and Projection Projected Achieved

  5. Polarization Performance: 100 GeV • Polarization transmission efficiency • negligible polarization loss during acceleration RUN 06 RUN 08 RUN 09

  6. Polarization Performance: 100 GeV • Polarization lifetime during store • No deterioration during store w/w.o spin rotator

  7. Polarization Performance: 250 GeV • Polarization loss between 100 GeV and 250 GeV • Measured with CNI polarimeter

  8. Polarization Tune Scan: 250 GeV acceleration 11/16 resonance 7/10 resonance 3/4 resonance Working pt for 250 GeV run in 2011 Working pt for 250 GeV run in 2009

  9. Polarization Tune Scan: 250 GeV acceleration • Accelerated 111 Yellow bunches to 100 GeV with vertical tune after tune swing at ~0.005 away from 1/3, with small beta* ~ 2m • Accelerated 111 Yellow bunches to 100 GeV with 0.2 mm radius wiggling for the whole ramp with vertical tune at 0.328. The closest distance between the modulated of the tune due to non-zero chromaticity reached ~0.0044. This data also demonstrated that this ramp has reasonably tolerance.

  10. Polarized Proton Luminosity Performance Courtesy of W. Fischer

  11. Major Plans for luminosity improvement • Dedicated 9MHz acceleration cavity : Brenann and Zaltsman • Provide better longitudinal match at injection to avoid the longitudinal emittance blowup • Longer bunch length during acceleration to reduce the peak bunch intensity. Hence, avoid transverse beam size blowup due to E-cloud • For a 1 ev-s beam, expected the bunch length rms ~ 1ns. • E-Lens: W. Fischer, Y. Luo and et al • Low energy electron beam to provide a focusing len to compensate the beam-beam induced tune spread • Allows higher bunch intensity • Non-linear chromaticity correction: Y. Luo and D. Trejbovic • Minimize chromatic tune spread • Reduce chromatic beta beat • Further beta squeeze

  12. Drell-Yan Experiment w. Colliding Beams • Drell-Yan with colliding beams: • Need high luminosity (how much?) • smaller beta* • Go to higher energy • Plan to explore the machine aspects in RUN 11. Establish additional collision at IP2: AnDY • Explore the impact off additional collision on luminosity lifetime • What’s the best time to turn on this collision? • Limit of Beta* at IP2

  13. Beta* consideration for AnDY • Field quality of triples in IR2 not as good as IR6 and IR8 • Local IR correctors installed in IR2 (like IR6 and IR8) but have currently no power supplies connectedhave used full complement in IR6/IR8 in operation: 6-poles, skew 6-poles, 8-poles, 10-poles, 12-poles • Small β* implies large βmax in triplets (β*βmax = const ~ 1.5 km) and therefore larger exposure of beam to triplet field errors • These cause emittance growth and beam lifetime reduction through the enhancement of chaotic particle motion (the reason for all beam loss)

  14. History of b* at IP2 • Have operated BRAHMS mostly with b* = 3.0 m (until Run-6) • Have also used • b* = 2.0 m (d-Au at 100 GeV/nucleon, Run-3, lifetime/background problems) • b* = 2.5 m (Cu29+ at 100 GeV/nucleon, Run-5, lifetime/background problems) • b* = 3.0 m (Cu29+ at 11.2 GeV/nucleon, Run-5) • b* = 3.0 m (31.2 GeV p, Run-6) • b* = 2.0 m possible (perhaps even b* = 1.0 m) • May need power supplies for local correctors • can be studied with dynamic aperture simulations (Y. Luo)

  15. Explore RHIC Energy Limit Energy increase by 30% (325 GeV) 30% increase in energy (to 325 GeV) appears possible • Arc dipoles have margin • Arc quadrupoles have even larger margin • Triplets have less margin M. Anerella et al., NIM A 499 (2003). 6500 A

  16. Exploring RHIC Energy Limit • Previous study, also looked at this for eRHIC (V. Ptitsyn) • Issues under investigation: • Training times of dipoles (arc, D0, DX) and quadrupoles (arc, triplet) • Main magnet PS upgrade • Transformers for main magnet PS • Current leads • Relaxation in b* • Crossing angle of 2 mrad • Polarization W. MacKay is working on a definite study.

  17. Accelerating Polarized Light Ions Magnetic field strength for 180o spin rotation: Reference to E. Courant’s RHIC/AP note

  18. Accelerating He3 in RHIC

  19. Accelerating He3+ in RHIC Gamma=62 Current dual snake configuration is no-longer sufficient for the last strong resonance with strength about ~0.8 Gamma=168

  20. Plan for Developing accelerating Polarized He3+ in RHIC • Detailed spin tracking • With orbit errors and synchrotron oscillation included • Provide guide line for tolerance on orbit distortions • Polarized He3 source development: • Newly commissioned Electron Beam Ion Source + polarized He3 gas can provide polarized He3 ion beam • An effort was initiated by MIT Bates group in joint with BNL experts • He3 polarimetry development: • Not yet started

  21. Accelerating Polarized Light Ions • Deuteron: • Can be to accelerate in the AGS with the combination of • Harmonic orbit correction to overcome imperfection resonances • RF dipole to overcome intrinsic resonances • Not practical to have it accelerated in RHIC to high energy • H3+: • Dual partial snake configuration in the AGS. However need to investigate the effect of horizontal resonances, more and stronger • Preserve polarization with horizontal tune jump • Spin match between AGS and RHIC • The resonance strength in RHIC may exceed what current dual snake setup allowance

  22. Summary • RHIC polarized proton performance has been improved significantly over the past decade • Expect 50% and higher polarization at 250 GeV with • H tune jump quads in the AGS • Source upgrade to yield 90% polarization • Accelerating pp with Qy at 0.19 in Yellow ring and Qy at 0.675 in Blue ring) from 100 GeV to 250 GeV • Future activities • Explore the DY experiment using collision at IP2 • Explore the energy limit of RHIC • Explore acceleration of polarized He3 beam

  23. RHIC interaction region with nonlinear correctors [F. Pilat et al., “Non-linear effects in the RHIC interaction regions, …”, PAC 2003.] Full corrector set (like IR6/IR8): 14 ps per beamReduced set (6-pole, skew 6-pole): 4 ps per beamAbout $12k per 50A ps (+infrastructure, controls, and installation: ~$100k)

  24. Luminosity Performance: 250 GeV • beta*: 0.7m, # of bunches: 109 • Bunch intensity: 1.1x10^11 protons • Peak luminosity: 85x10^30 cm^-2s^-1 • Average luminosity: 55x10^30 cm^-2s^-1

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