RHIC polarized protons – The next decade – Wolfram Fischer 14 May 2010 RSC Meeting, Iowa State University.
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RHIC polarized protons – The next decade – Wolfram Fischer 14 May 2010 RSC Meeting, Iowa State University
Content 1.Run-9 performance (short) 2.Run-11 upgrade plans and projections (short) 3.Longer-term upgrade plans Polarization Luminosity Energy Wolfram Fischer2
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) Wolfram Fischer3
4 Luminosity and polarization goals Parameterunit AchievedEnhanced design Next L upgrade p - p operation (2009) ( 2011/12)( 2014) Energy GeV 100 / 250 250 No of bunches … 109 Bunch intensity 10 11 1.3 / 1.11.3 / 1.52.0 Average L 10 30 cm -2 s -1 24 / 5530 / 150300 Polarization P % 55 / 3470 Had previously a goal of 60 here. (May reach 60 with source upgrade and electron lenses).
Run-9 250 GeV p -p Run Coordinator: M. Bai Wolfram Fischer5 First collider operation with polarized protons at 250 GeV P = 34% (H-jet online)
Run-9 100 GeV p -p Run Coordinator: C. Montag Wolfram Fischer6 Little progress compared to Run-6 / Run-8 - L peak higher by up to 40% (lower and * ) - DOES NOT lead to increased L avg P = 55% (H-jet online)
RHIC calendar time in store Wolfram Fischer7 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 (tested in Run-9 and Run-10) 2.RHIC: polarization transmission to 250 GeV acceleration near 2/3 resonance (tested in Run-10) 3.RHIC: intensity transmission to 250 GeV beam dump system modifications (thicker beam pipe in dump) Yellow ramp transmission (9 MHz rf system) 4.RHIC: peak luminosity and luminosity lifetime reached lower * limit at 100 GeV (not necessarily a problem at 250 GeV) electron lenses allow for larger beam-beam parameter Wolfram Fischer8
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 solenoid 3. Beam diagnostics and polarimetry Wolfram Fischer9
RHIC OPPIS produces reliably 0.5-1.0mA polarized H - ion current. Polarization at 200 MeV: P = 80-85%. Beam intensity (ion/pulse) routine operation: Source - 10 12 H - /pulse Linac - 5∙10 11 AGS - 1.5-2.0 ∙ 10 11 RHIC - 1.5∙10 11 29.2 GHz ECR source used for primary proton beam generation source was originally developed for dc operation 10x intensity increase was demonstrated in a pulsed operation by using a very high-brightness Fast Atomic Beam Source instead of the ECR source Optically Pumped Polarized H – source at RHIC – A. Zelenski
The ECR primary proton source replacement with the very high- brightness Fast Atomic Beam Source. Atomic H injector development in collaboration with BINP, Novosibirsk. New superconducting solenoid (3.0 T long flattop). He – ionizer cell serves as a proton source in the high magnetic field. H+H+ H0H0 H-H- H0H0 H+H+ OPPIS upgrade with Fast Atomic Beam Source – A. Zelenski
He – ionizer cell serves as a proton source in the high magnetic field. H+H+ H0H0 H-H- H0H0 H+H+ The source produces ~ 3 A ! (pulsed) proton current at 5.0 keV. ~ 10 mA H- current, P = 85-90%. ~ 300 mA (high-brightness) unpolarized H - ion current. OPPIS upgrade with Fast Atomic Beam Source – A. Zelenski
Polarized protons from AGS Wolfram Fischer13 Courtesy H. Huang Intensity dependent polarization in AGS in Run-6 and Run-9 AGS horizontal tune jump system: first test in 2009, Tests in 2010: Better understanding of emittance growth mechanism ( -beat) ®up to 5% more polarization Working on orbit feed forward for better reproducibility.
RHIC polarization transmission to 250 GeV Wolfram Fischer14 Courtesy M. Bai At current working point limited tune space between 2/3 (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.)
RHIC polarization transmission to 250 GeV Wolfram Fischer15 Test with Au beam in Run-10 (M. Bai et al.) Successful acceleration with Q = 0.005 Q = 0.005 corresponds to >90% polarization transmission. Simulations started to compare DA of Au lattice 2010 with proton lattice for 2011 (Y. Luo, X. Gu).
Beam dump Problem: Quenched Q4 after beam dump several times with high intensity beam close to 250 GeV beam energy (also with Au beam recently) Simulations by K. Yip, with L. Ahrens: Increase of kick strength by 20% (6 th kicker module) should allow 20% increase in intensity Replacement of dump beam pipe should allow 100% increase in intensity Summer 2010 shut-down: Will install new beam pipe in dump (2x thicker) Wolfram Fischer16
RHIC Yellow ramp transmission Wolfram Fischer17 Ramp transmission [%] Sharp drop in Yellow ramp transmission for 150 10 11 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, and in-situ coating.
Further upgrades for p -p performance Orbit control on ramp (global, ~1 Hz) reduces number of lost ramp during development at store slow (global, ~1 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 system requires 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 Polarimetry CNI 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 Wolfram Fischer18
Further upgrades for p -p performance Spin flipper need modifications to eliminate global effects (installed in Run-10) Collimation efficiency studied 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 reliability periodic review and upgrades based on observed failure statistics 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 Fischer19
Orbit control – global orbit feedback (~1 Hz) Wolfram Fischer20 M. Minty et al., IPAC10 Global orbit feedback successfully demonstrates (at store and on ramp) Allows for faster ramp development, better ramp and store orbit maintenance with diurnal orbit changes.
10 Hz global orbit feedback – R. Michnoff et al. Wolfram Fischer21 Expect improvements in luminosity lifetime. [Necessarily of near-integer working point.] March 24, 2010 Feedback OFF Feedback ON IR6 and IR8 Blue Q1 and Q3 horizontal BPM measurements with 10 Hz feedback ON vs. OFF (31.2 GeV Gold) Position in triplet [ m]
Spin flipper – M. Bai et al. Wolfram Fischer22 AC and DC dipoles worked as expected Coherent oscillation of Blue beam was global and had effect on Yellow beam Tested orbit effect in Run-10 (successful)
Electron lenses in RHIC Wolfram Fischer23 e-beam p-beam Additional head-on beam-beam collision with electron beam can partially compensate beam-beam effect from other proton beam. 2 electron lenses are under construction goal of 2x luminosity increase together with source upgrade plan to start using in Run-13
Electron lenses in RHIC Wolfram Fischer 24 6D beam lifetime simulation of electron lens (Y. Luo, IPAC10) N b = 3x10 11 without and with e-lens Simulations show full benefit of e-lens for N b > 2x10 11 (i.e. with source upgrade) Beam lifetime simulations are challenging – Require good model and supercomputer
R&D for in-situ coating of arc beam pipes Electron clouds limit proton emittance at injection, ramp transmission (Yellow) Warm parts are largely coated with NEG Cold arcs are stainless steel, not coated Need in-situ coating for arcs Wolfram Fischer25 R&D for magnetron mole Test tube coated with Cu A. Hershkovich et al. IPAC10
Energy increase by 30% (325 GeV) Wolfram Fischer26 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
Energy increase by 30% (325 GeV) Wolfram Fischer27 Previous study, also looked at this for eRHIC (V. Ptitsyn) Upgrades needed to: Main magnet PS Transformers for main magnet PS Current leads … Operation may require: Crossing angle of 2 mrad Relaxation in * Working on definite study – should balance cost with luminosity need. Luminosity guidance helpful.
Wolfram Fischer28 Luminosity and polarization goals Parameterunit AchievedEnhanced design Next L upgrade p - p operation (2009) ( 2011/12)( 2014) Energy GeV 100 / 250 250 No of bunches … 109 Bunch intensity 10 11 1.3 / 1.11.3 / 1.52.0 Average L 10 30 cm -2 s -1 24 / 5530 / 150300 Polarization P % 55 / 3470 Had previously a goal of 60 here. (May reach 60 with source upgrade and electron lenses).
Run-11 p -p luminosity projections 100 GeV Wolfram Fischer29 Expect store polarization of 50-65%, and average store luminosity of up to 30 10 30 cm -2 s -1. [Projections update 11 May 2010.]
Run-11 p -p luminosity projections 250 GeV Wolfram Fischer30 Expect store polarization of 35-50%, and average store luminosity of up to 100 10 30 cm -2 s -1. [Projections update 11 May 2010.]
Spin plan update projections Wolfram Fischer31 Spin plan update, 06/09/2008 [Assumes 10 week p -p operation every year.]