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 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, …

SpinFest, August 7,

Summary of Achieved Performance and Projection p  - p  operation 2006(2009)(2011/12)(2014) Energy GeV / No of collisions … Bunch intensity / / Beta*m / Average L10 30 cm -2 s / 5530 / Polarization P % / 3570 Achieved Projected

Polarization Performance: 100 GeV  Polarization transmission efficiency -negligible polarization loss during acceleration RUN 06 RUN 08RUN 09

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

Polarization Performance: 250 GeV  Polarization loss between 100 GeV and 250 GeV -Measured with CNI polarimeter

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

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 The closest distance between the modulated of the tune due to non-zero chromaticity reached ~ This data also demonstrated that this ramp has reasonably tolerance.

Polarized Proton Luminosity Performance Courtesy of W. Fischer

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

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

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 connected have 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) Wolfram Fischer

History of  * at IP2 Wolfram Fischer Have operated BRAHMS mostly with  * = 3.0 m (until Run-6) Have also used  * = 2.0 m (d-Au at 100 GeV/nucleon, Run-3, lifetime/background problems )  * = 2.5 m (Cu 29+ at 100 GeV/nucleon, Run-5, lifetime/background problems)  * = 3.0 m (Cu 29+ at 11.2 GeV/nucleon, Run-5)  * = 3.0 m (31.2 GeV p, Run-6)  * = 2.0 m possible (perhaps even  * = 1.0 m) May need power supplies for local correctors – can be studied with dynamic aperture simulations (Y. Luo)

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

Exploring RHIC Energy Limit Wolfram Fischer 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  * Crossing angle of 2 mrad Polarization W. MacKay is working on a definite study.

Accelerating Polarized Light Ions speciesg-2/2Resonanc e spacing[G eV/u] Snake strength[ T-m] Keep Polarization in the AGS Keep Polarization in RHIC p Dual partial snakes Dual full snakes d Harmonic correction + RF dipole Very difficult preserving polarization as well as spin manipulation H Dual partial snakes Dual snake+precise orbit and optics control He Dual partial snakes Dual snake+precise orbit and optics control Reference to E. Courant’s RHIC/AP note Magnetic field strength for 180 o spin rotation:

Accelerating He3 in RHIC

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

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

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

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 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

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

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