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Polarized Proton Acceleration and Collisions

Polarized Proton Acceleration and Collisions. Spin dynamics and Siberian Snakes Polarized proton acceleration in AGS and RHIC Possible RHIC proton-proton luminosity upgrades Polarized proton acceleration in HERA. Spinning Quarks or Gluons. Spinning Proton. Spinning Proton.

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Polarized Proton Acceleration and Collisions

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  1. Polarized Proton Acceleration and Collisions Spin dynamics and Siberian Snakes Polarized proton acceleration in AGS and RHIC Possible RHIC proton-proton luminosity upgrades Polarized proton acceleration in HERA

  2. Spinning Quarks or Gluons Spinning Proton Spinning Proton Quark, Gluon, Photon, Electron or Neutrino from W or Z Decay RHIC Spin Physics • Spin structure functions of gluon and anti-quarks • Parity violation in parton-parton scattering

  3. Spin Dynamics • Precession Equation in Laboratory Frame: • (Thomas [1927], Bargmann, Michel, Telegdi [1959]) • dP/dt = - (e/gm) [GgB + (1+G) B ] P • Lorentz Force equation: • dv/dt = - (e/gm) [ B ] v • For pure vertical field:Spin rotates Gg times faster than motion, nsp = Gg • For spin manipulation:At low energy, use longitudinal fieldsAt high energy, use transverse fields

  4. Depolarizing Spin Resonances Spin tune: Number of 360 degree spin rotations per turn Depolarizing resonance condition: Number of spin rotations per turn = Number of spin kicks per turn Imperfection resonance (magnet errors and misalignments): Gg = nsp = n Intrinsic resonance (Vertical focusing fields): Gg = nsp = Pn ±ny P: Superperiodicity [AGS: 12] ny: Betatron tune [AGS: 8.75]

  5. Siberian Snakes (Local Spin Rotators) cos(180 nsp) = cos(d/2) · cos(180 Gg) d 0 nsp  n No imperfection resonances Partial Siberian snake (AGS) d= 180 nsp = ½ No imperfection resonances and No Intrinsic resonances Full Siberian Snake Two Siberian Snakes in RHIC

  6. (Naïve) Limits for Siberian Snakes • Spin rotation of Siberian snake > Spin rotation of driving fields • Imperfection resonances e Energy • Intrinsic resonances eEnergy • Partial Siberian snake(AGS, d = 9 )e = d/360 • One full snakee = 1/2 • Two full snakes(RHIC)e = 1 • N full snakes(HERA, LHC)e = N/2

  7. BRAHMS & PP2PP (p) PHENIX (p) STAR (p) Polarized proton collisions in RHIC RHIC pC Polarimeters Absolute Polarimeter (H jet) Siberian Snakes Spin Rotators 2  1011 Pol. Protons / Bunch e = 20 p mm mrad Partial Siberian Snake LINAC BOOSTER Pol. Proton Source 500 mA, 300 ms AGS AGS Internal Polarimeter 200 MeV Polarimeter Rf Dipoles

  8. High intensity polarized H- source KEK OPPIS upgraded at TRIUMF 75 - 80 % Polarization 151011 protons/pulse at source 61011 protons/pulse at end of LINAC

  9. Proton polarization at the AGS • Full spin flip at all imperfectionresonances using partial Siberian snake • Full spin flip at strong intrinsic resonances using rf dipole • Remaining polarization lossfrom coupling and weakintrinsic resonances • New tune working point and smaller horizontal emittancewill reduce polarization loss

  10. First Siberian Snake in RHIC Tunnel Siberian Snake: 4 superconducting helical dipoles, 4Tesla, 2.4 m long with full 360 twist Funded by RIKEN, Japan Designed and constructed at BNL

  11. Commissioning with a single snake in RHIC Gg = 48 or 60.3 Gg = 46.5 or 55.7 -12º polarimeter • Inject vertically pol. beam with snake off • Turn on snake  Horizontally pol. beam • Accelerate snake

  12. Polarized proton injection into RHIC Injection at Gg = 46.5 without snake: vertical polarization! ny = 29.11 Sensitive to betatron tune setting ny = 29.23

  13. Single snake RUN2000 B1 = B2 Two snakes for RUN2001 Snake operating points

  14. Acceleration with single snake Gg=48.0 Gg=46.5 Gg=60.3 Gg=55.7

  15. Measured RHIC asymmetries P  19 % P  40 % at AGS Asymmetry ( 10-3) Gg 24.3 25.1 29.1 31.5 GeV

  16. Spin resonances in RHIC (w/o Snakes) Inj. Energy Gg = 46.5 E = 24.3 GeV Gg = 60.3 E = 31.5 GeV Gg = 55.7 E = 29.1 GeV Gg = 48

  17. Spin tracking with single snake (single particle) rms orbit distortions: ___ 0 mm ___ 1 mm ___ 2 mm Need well corrected orbit! Longitudinal beam polarization opposite of snake Strong spin resonance Radial beam polarization at the polarimeter

  18. Typical closed orbits at injection Before correction After correction

  19. Spintracking trough strongest RHIC resonance Whole beam • Two Siberian snakes • 1 mm rms misalignment(Survey: < 0.5 mm) • 0.2 mm rms closed orbit • 20 pmm emittance (95%)(~ 10 pmm in RUN2000 ) Edge particle

  20. Polarized proton status and plans (1) • FY2000 run: • Single Siberian snake and pC polarimeter installed in blue ring • New polarized proton source: ~ 1012 pol. protons/pulse • Accelerated polarized beam in blue ring • FY2001/ FY2002 run: • All four Snakes and pC polarimeters installed in blue and yellow ring • Goal: 100 GeV100 GeV collision with long. pol. at interaction regions Accelerate with two Snakes Collide beams with one Snake per ring for longitudinal polarization Polarization:  50 % 1011 protons per bunch; 60 bunches; b* = 2 m; L = 5 ´ 1030 cm-2 s-1Integrated luminosity per week : 1.5 (pb)-1 (50% availability) Accelerate polarized beam to 250 GeV

  21. Polarized proton status and plans (2) • FY2003 run: • All eight spin rotators installed • Goal: 250 GeV250 GeV collision with long. pol. at STAR and PHENIX • FY2004 run: • Polarized hydrogen jet target for absolute polarimetry installed

  22. Luminosity Upgrades • RHIC Spin RHIC II Future Upgrade • Emittance(95%) pmm 20 1212 • Beta function at IR [m] 1 1 0.3 • Number of bunches 120 120 360 • Bunch population [1011] 2 2 2 • Beam-beam parameter per IR 0.007 0.012 0.012 • Angular size at IR [mrad] 112 86 157 • RMS beam size at IR [mm] 112 86 47 • Luminosity [1032 cm-2 s-1] 2.4 4.0 40.0 • RUN2000: Au-Au luminosity: 3.31025 cm-2 s-1 [N-N luminosity ~ 1030 cm-2 s-1 ] • RHIC II : Beam-beam tune shift limited for 2 interaction regions • Future Upgrade: Mini-beta quads and more bunches • Will also require major detector upgrades

  23. Polarized protons in HERA • Difficulties for polarized protons in HERA • Not perfect symmetry • Vertical bends (Remedy: flattening Snakes) • Not built for polarization • Hardly space for more than 4 Siberian Snakes • Very high energy (920 GeV) and spin tune (1758)

  24. Invariant spin field

  25. Requirements and installation

  26. Summary • Very successful first RHIC spin commissioning run: • RHIC Polarimeter commissioned • Single Siberian snake works • With two snakes per ring and improved tune and orbit control during acceleration expect 100 GeV on 100 GeV polarized proton collisions this year. • Collisions of polarized protons at 500 GeV and 2  1032 cm-2 s-1 possible by FY2004 • Luminosity upgrade for RHIC possible to 4  1033 cm-2 s-1

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