RHIC Accelerator Capability: Present and Future Mei Bai Collider Accelerator Dept. BNL.
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Transcript of 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, …
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
7/10
reso
nanc
e
11/1
6 re
sona
nce
3/4 resonance
Wor
king
pt f
or 2
50 G
eV ru
n in
200
9
Wor
king
pt f
or 2
50 G
eV ru
n in
201
1
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.
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
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)