RHIC polarized proton performance and upgrade plans Wolfram Fischer

1. RHIC polarized proton performance and upgrade plansWolfram Fischer 11 November 2009 RSC Meeting, Berkeley

2. Content • Run-9 performance • Run-11 upgrade plans and projections • Longer-term upgrade plans 2

3. 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) 3

4. Luminosity and polarization goals Had previously a goal of 60 here.

5. Run-9 250 GeV p-pRun Coordinator: M. Bai First collideroperation with polarizedprotons at 250 GeV P= 34%(H-jet online) 5

6. Run-9 100 GeV p-pRun Coordinator: C. Montag • Little progresscompared to Run-6 / Run-8 • Lpeak higher by up to 40% (lower e and b*) • DOES NOT lead to increased Lavg P= 55%(H-jet online) 6

7. RHIC calendar time in store goal expectation After improvements in Run-8, time in store fell back in Run-9.Should assume 55% on average for future runs. 7

8. Main limits for p-p performance and possible solutions • 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) • RHIC: polarization transmission to 250 GeV acceleration near 2/3 resonance (tests in Run-10) • RHIC: intensity transmission to 250 GeV beam dump system modifications (stronger kick, Q4 shielding) Yellow ramp transmission (9 MHz rf system) • RHIC: luminosity lifetime at 100 GeV reached lower b* limit at 100 GeV(not necessarily a problem at 250 GeV) 8

9. 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 9

10. Polarized protons from AGS 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 Courtesy H. Huang 10

11. RHIC polarization transmission to 250 GeV 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.) Courtesy M. Bai 11

12. 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) 12

13. RHIC Yellow ramp transmission Ramp transmission [%] Ramp transmission [%] Sharp drop in Yellow ramp transmission for  1501011 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 13

14. RHIC luminosity lifetime at 100 GeV Luminosity fitted to L(t) = A*exp(-t/t1) + (1-A)*exp(-t/t2) [first 3h] [fast decay, t10.5h] [slow decay] b* = 1.0 m 1.0 m 0.7 m Re-established beam lifetimes with b* = 1.0=> Reached lower b* limit at 100 GeV 14

15. RHIC luminosity lifetime at 100 GeV • Beam lifetime dominated by: beam-beam, IR magnet errors, parameter modulations • Reached a limit in beam-beam parameter (x = 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)  Need high order corrections to improve luminosity lifetime. Future larger improvements expected from successful implementation of electron lenses (AIP under way) 15

16. 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 • b* reduction to 0.5 m (perhaps 0.35 m)requires improvements in lattice corrections 16

17. 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 (x=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) 17

18. 10 Hz global orbit feedback – R. Michnoff et al.  oscillation in triplet network  corrector magnet development(P. Thieberger) 18

19. Spin flipper – M. Bai et al. • AC and DC dipoles worked as expected • Coherent oscillation of Blue beam was global and had effect on Yellow beam 19

20. Electron lenses in RHIC • 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 2011 • Goal: • partially compensate head-on beam-beam effect • about factor 2 in luminosity improvement (with source upgrade) 20

21. Collimation upgrade – simulation by G. Robert-Demolaize Comparison of collimation in IR12 with IR12+masks (vertical) Masks are promising (no results yet with existing collimation). 21

22. Run-11 p-p luminosity projections 100 GeV Expect store polarization of 50-65%, and average store luminosity of up to 301030cm-2s-1. 22

23. Run-11 p-p luminosity projections 250 GeV Expect store polarization of 35-50%, and average store luminosity of up to 1001030cm-2s-1. Higher polarization likely requires new working point. 23

24. Spin plan update projections Spin plan update, 06/09/2008 24

25. 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, P = 50 – 65% • For 250 GeV: 18 – 34 pb-1/week, P = 35 – 50% • Further upgrades (all  2012): • Beam dump upgrade • Polarized source upgrade • Electron lenses • Collimator upgrade • 56 MHz SRF system 25