RHIC Accelerator Capability: Present and Future

Mei BaiCollider 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, …

PHENIX (p)

AGS

LINACBOOSTER

Pol. H- Source

Solenoid Partial Siberian Snake

200 MeV Polarimeter

Helical Partial Siberian Snake

Spin Rotators(longitudinal polarization)

Siberian Snakes

Spin Rotators(longitudinal polarization)

Strong AGS Snake

RHIC pC PolarimetersAbsolute Polarimeter (H jet)

STAR (p)

BRAHMS(p)

AGS Polarimeters

Spin flipper

SpinFest, August 7, 20083

Summary of Achieved Performance and Projection

p- p operation 2006 (2009) (2011/12) (2014)

Energy GeV 100 100 / 250 100 / 250 250

No of collisions … 109 107 107 107

Bunch intensity 1011 1.3 1.3 / 1.1 1.3 / 1.5 2.0

Beta* m 1.0 0.7 0.7/0.4 0.3

Average L 1030cm-2s-1 18 28 / 55 30 / 150 300

Polarization P % 55 56 / 35 70 70

Achieved Projected

Polarization Performance: 100 GeV

Polarization transmission efficiency- negligible polarization loss during acceleration

RUN 06RUN 08 RUN 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

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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.

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 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)

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 (Cu29+ at 100 GeV/nucleon, Run-5, lifetime/background problems)

• * = 3.0 m (Cu29+ 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 LimitEnergy 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

species g-2/2 Resonance

spacing[GeV/u]

Snake strength[

T-m]

Keep Polarization in

the AGS

Keep Polarization in RHIC

p 1.793 0.523 5.845 Dual partial snakes

Dual full snakes

d -0.143 6.58 147 Harmonic correction + RF

dipole

Very difficult preserving

polarization as well as spin manipulation

H3 7.937 0.118 3.961 Dual partial snakes

Dual snake+precise orbit and optics

control

He3 -4.191 0.218 3.751 Dual partial snakes

Dual snake+precise orbit and optics

control

€

BL(π ) =10.48A

ZG

Reference to E. Courant’s RHIC/AP note

Magnetic field strength for 180o spin rotation:

Accelerating He3 in RHIC

Accelerating He3+ in RHIC

Gamma=62

Gamma=168

Current dual snake configuration is no-longersufficient for the last strong resonance withstrength 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 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

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 beamReduced 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