RHIC polarized proton performance and upgrade plans

Wolfram Fischer

11 November 2009RSC Meeting, Berkeley

Content

1.Run-9 performance

2.Run-11 upgrade plans and projections

3.Longer-term upgrade plans

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Run-9 polarized protons

250 GeV• First colliding beam operation at 250 GeV• Upgraded CNI polarimeter• Magnet re-alignment near snakes• LEBT/MEBT modification (25% smaller emittance in RHIC)

• Improved nonlinear chromaticity correction• Test of 9 MHz acceleration rf system • Triplet 10 Hz cold mass measurements

100 GeV• First test of AGS horizontal tune jump system• Test of new low level rf system• Tests of spin flipper• All RHIC service buildings with A/C• Operational use of 10- and 12-poles (Yellow beam lifetime)

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Luminosity and polarization goals

Parameter unit Achieved Enhanced design

Next upgrade

Au-Au operation (2007) ( 2012)

Energy GeV/nucleon 100 100 100No of bunches … 103 111 111Bunch intensity 109 1.1 1.0 1.0Average 1026cm-2s-1 12 8 40p- p operation (2009) ( 2011/12) ( 2014)

Energy GeV 100 / 250 100 / 250 250No of bunches … 109 109 109Bunch intensity 1011 1.3 / 1.1 1.3 / 1.5 2.0Average 1030cm-2s-1 24 / 55 30 / 150 300Polarization % 55 / 34 70 70

Had previously a goal of 60 here.

Run-9 250 GeV p-p Run Coordinator: M. Bai

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First collideroperation with polarizedprotons at 250 GeV

= 34%(H-jet online)

Run-9 100 GeV p-p Run Coordinator: C. Montag

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Little progresscompared to Run-6 / Run-8

- peak higher by up to 40% (lower and *)

- DOES NOT lead to increased avg

= 55%(H-jet online)

RHIC calendar time in store

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goal

After improvements in Run-8, time in store fell back in Run-9.Should assume 55% on average for future runs.

expectation

Main limits for p-p performance and possible solutions

1. AGS : proton bunches with high intensity, high polarization and low emittance

polarized source upgrade (under way) AGS horizontal tune jump system (further tests in Run-10)

2. RHIC: polarization transmission to 250 GeV acceleration near 2/3 resonance (tests in Run-10)

3. RHIC: intensity transmission to 250 GeV beam dump system modifications (stronger kick, Q4 shielding) Yellow ramp transmission (9 MHz rf system)

4. RHIC: luminosity lifetime at 100 GeV reached lower * limit at 100 GeV (not necessarily a problem at 250 GeV)

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Polarized source upgrade – A. Zelenski

• 3-year capital project (started in FY 2009)

• Goals:1. H-ion beam current increase to 10mA (order of magnitude)2. Polarization to 85-90% (5% increase)

• Upgrade components:1. Atomic hydrogen injector (collaboration with BINP Novosibirsk)2. Superconducting solenoid3. Beam diagnostics and polarimetry

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Polarized protons from AGS

Wolfram Fischer 10 Courtesy H. Huang

Intensity dependent polarization in AGS in Run-6 and Run-9

AGS horizontal tune jumpsystem: first test in 2009, further tests in 2010

up to 5% more polarization

RHIC polarization transmission to 250 GeV

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At current working point limited tune space between2/3 (beam loss) and 7/10 (polarization loss) on ramp.

Need to test acceleration closer to 2/3 in Run-10 with Au.(Near integer WP less promising at this point.)

Beam dump

Problem: • Quenched Q4 after beam dump several times with high

intensity beam close to 250 GeV beam energy

Simulations by K. Yip, with L. Ahrens:• Increase of kick strength by 20% (6th kicker module)

should allow 20% increase in intensity Sufficient for Run-11, but not long-term working on estimate for abort kicker upgrade

• Now investigating:- beam pipe insert or other mask in front of Q4- beam dump outside ring beam line if needed (within or outside tunnel)

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RHIC Yellow ramp transmission

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Sharp drop in Yellow ramp transmission for 1501011 p

Better transmission for same intensity in fewer bunches suggest electron clouds as contributing mechanism (V. Schoefer, APEX09),

can be mitigated with 9 MHz rf

RHIC luminosity lifetime at 100 GeV

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Luminosity fitted to L(t) = A*exp(-t/t1) + (1-A)*exp(-t/t2) [first 3h]

* = 1.0 m 1.0 m 0.7 m

Re-established beam lifetimes with * = 1.0=> Reached lower * limit at 100 GeV

[fast decay, t10.5h] [slow decay]

RHIC luminosity lifetime at 100 GeV

Beam lifetime dominated by: beam-beam, IR magnet errors, parameter modulations

• Reached a limit in beam-beam parameter ( = 0.007/IP)• Nonlinear chromaticity corrections in place• Have used 6-pole and skew 6-pole IR correctors already in past• Have used 10- and 12-pole

correctors in Yellow for the first time operationally in Run-9 (4%/ring increase in integrated store luminosity)

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Need high order corrections to improve luminosity lifetime. Future larger improvements expected from successful implementation of electron lenses (AIP under way)

Further upgrades for p-p performance• Orbit control

• on ramp (global, 0.5 Hz) reduces number of lost ramp during development

• at store slow (global, 0.5 h, 24 h vertical movement) tighter tolerances at 250 GeV (IP, collimators)

• at store fast (global, 10 Hz, triplet vibrations) reduces parameter (e.g. tune) modulation

• 9 MHz rf systemrequires upgrade of RMMPS flattop-to-ramp switches,and independent Blue and Yellow longitudinal dampers preserves longitudinal and transverse emittances better on ramp, mitigation of Yellow intensity ramp transmission limit

• PolarimetryCNI polarimeter (rate dependence, setup time)additional polarimeter in IP10 with collision

* reduction to 0.5 m (perhaps 0.35 m)requires improvements in lattice corrections

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Further upgrades for p-p performance

• Spin flipperneed modifications to eliminate global effects (under way)

• Collimation efficiencystudied with simulation move of collimator to IR12 (G. Robert-Demolaize, A. Drees) – gain not very large, alternatively study additional masks in experimental IRs

• Electron lenses increase of beam-beam parameter – now at limit (=0.007/IP)

• In-situ beam-pipe coating for lower SEY(R&D)A. Hershkovich working with company (SBIR) high risk R&D, but would reduce all e-cloud phenomena

• Maintain/improve reliabilityperiodic review and upgrades based on observed failurestatistics and expected end-of-life failures expect 55% of calendar time in store in future run (on average)

…

• Cooling at store energy (CeC R&D – V. Litvinenko)Wolfram Fischer 17

10 Hz global orbit feedback – R. Michnoff et al.

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oscillation in triplet

corrector magnet development (P. Thieberger)

network

Spin flipper – M. Bai et al.

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• AC and DC dipoles worked as expected• Coherent oscillation of Blue beam was global and had effect on Yellow beam

2800.0

Electron lens layout

2500.0

Pick-up electrodes

Superconducting solenoid

Transverse coils

Guiding coil

RHIC beam line

Electron gun

Electron gun coil

8" gate valve

Turbopump

Intermediate coil

Gate valve

Electron collector (EC)

Electron reflector

Ceramic break10" gate valve

EC magnet coilTransverse coils

Electron suppressorHV ceramic break

Isolated drift tubes

Cryopump

Electron lenses in RHIC

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Status:• main solenoid (superconducting) bids due 11/25 • collector designed• gun and e-transport under design (cathodes to be out for bid)• plan for completion by end of 2011Goal: • partially compensate head-on beam-beam effect• about factor 2 in luminosity improvement (with source upgrade)

Collimation upgrade – simulation by G. Robert-Demolaize

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Comparison of collimation in IR12 with IR12+masks (vertical)

Masks are promising (no results yet with existing collimation).

Run-11 p-p luminosity projections 100 GeV

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Expect store polarization of 50-65%, and average store luminosity of up to 301030cm-2s-1.

Run-11 p-p luminosity projections 250 GeV

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Expect store polarization of 35-50%, and average store luminosity of up to 1001030cm-2s-1.

Higher polarization likely requires new working point.

Spin plan update projections

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Spin plan update, 06/09/2008

Summary

Planned upgrades for Run-11:• AGS horizontal tune jump system• Acceleration near 2/3• Beam dump upgrade• 10 Hz orbit feedback • 9 MHz rf system• Spin flipper upgrade

Projections for Run-11• For 100 GeV: 6 – 10 pb-1/week, = 50 – 65%• For 250 GeV: 18 – 34 pb-1/week, = 35 – 50%

Further upgrades (all 2012):• Beam dump upgrade• Polarized source upgrade• Electron lenses• Collimator upgrade • 56 MHz SRF system

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