Polarized Proton Acceleration and Collisions

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
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? (1G) B? ? P
• Lorentz Force equation
• dv/dt - (e/gm) B? ?
  v
• For pure vertical fieldSpin rotates Gg times
  faster than motion, nsp Gg
• For spin manipulationAt 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 gt Spin rotation
  of driving fields
• Imperfection resonances e ? Energy
• Intrinsic resonances e ? ?Energy
• Partial Siberian snake (AGS, d 9? ) e d/360?
• One full snake e 1/2
• Two full snakes (RHIC) e 1
• N full snakes (HERA, LHC) e N/2

7
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
Snake operating points
14
Acceleration with single snake
Gg48.0
Gg46.5
Gg60.3
Gg55.7
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 lt 0.5 mm)
• 0.2 mm rms closed orbit
• 20 p mm emittance (95)( 10 p mm 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-1 Integrated 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 12 12
• 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