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Proton Polarimetry

Proton Polarimetry. Proton polarimeter reactions RHIC polarimeters. Proton polarimeters for circulating beams. p + C  p + X Good FOM at low energy (< 3GeV) [COSY] p + p  p + p (t ~ 0.15 GeV 2 ) Good FOM up to ~ 20 GeV [AGS] Plastic target: intensity beams limited

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Proton Polarimetry

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  1. Proton Polarimetry Proton polarimeter reactions RHIC polarimeters

  2. Proton polarimeters for circulating beams • p + C  p + X Good FOM at low energy (< 3GeV) [COSY] • p + p  p + p (t ~ 0.15 GeV2) Good FOM up to ~ 20 GeV [AGS] • Plastic target: intensity beams limited • p + C p + X (x~0.5,pt~0.5 GeV) Good FOM at high energy • Requires large spectrometer • p + p  p + p (t ~ 0.001 GeV2) Good FOM at all energies [RHIC abs. pol.] • Jet target: low luminosity • Pol. H jet: absolute polarimeter • p + C  p + C (t ~ 0.001 GeV2) Good FOM at all energies [RHIC rel. pol.] • Carbon target: high luminosity • Good and fast relative polarimeter

  3. 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

  4. 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

  5. Silicon detector Recoil Carbon, 100 … 800 keV Target Out Target In Polarized Proton Beam Forward proton Ultra-thin Carbon ribbon approx. 100 atomic layers thick Carbon TDC distribution ADC distribution Proton-Carbon CNI Polarimeter (AGS E950) • 2-3% energy independent analyzing power for small-angle elastic scattering in the Coulomb-Nuclear Interference (CNI) region • Slow recoil Carbon detected in between bunch crossings • Fiber target allows for polarization profile measurement

  6. Elastic scattering in small t region (0.002<t<0.05) (GeV/c)2 • Large cross section • Simple equipment • Weak energy dependence of the asymmetry • Fast measurement • Small influence on the beam by the target • Small analyzing power (1-4)% • No precise theoretical predictions Physical asymmetry (cancels acceptance and luminosity asymmetries)

  7. E950 setup A RIKEN BNL Research Center Workshop Carbon ribbon target (3.7 mg/cm2, 6 mm) 1 cm Silicon strip detector (6  4 mm) Electrostatic mirror • DAQ: • LeCroy FERA ADC 4300 • LeCroy 2367 as FERA memory • IBM/PC with Linux • Readout between spills • Dead time 15ms per event Carbon foil (3.7 mg/cm2) • AGS internal beam: • 5·109 p/bunch • 1 bunch in the ring: 2.7 ms between bunches • Bunch length  25 ns • 22 GeV • Polarization 40% BNL-2001

  8. A RIKEN BNL Research Center Workshop A RIKEN BNL Research Center Workshop A RIKEN BNL Research Center Workshop E950 results A RIKEN BNL Research Center Workshop A=0.005330.00027 2/Ndf ~ 1 BNL-2001

  9. RHIC year-0 detector set-up bluering • Thin carbon target ~ 5 g/sm2  10m; • Horizontal and vertical targets; • 4 Detectors 12strips  2 mm; • Strips in vertical direction; • Trigger as ‘or’ of all strips; • DAQ with LeCroy FERA 4300 ADC/TDC; • Dead time ~ 10 s per event + 1.5s per 40000 events; • 6-bunch mode; • Upto 51010 p/bunch; • About 105 carbon events/min; 1 3 15 cm 4 2 1 12 Carbon identification by time of flight/energy dependence: E, keV -t (GeV/c)2 T, ns 100 0.0022 118 200 0.0045 84 500 0.0112 53 1000 0.0223 37 2000 0.0446 27

  10. A RIKEN BNL Research Center Workshop A RIKEN BNL Research Center Workshop A RIKEN BNL Research Center Workshop Data A RIKEN BNL Research Center Workshop Carbon over strips distribution C  BNL-2001

  11. A RIKEN BNL Research Center Workshop A RIKEN BNL Research Center Workshop A RIKEN BNL Research Center Workshop Energy calibration A RIKEN BNL Research Center Workshop • Energy calibration of the detector by the time of flight • Agreement with the Tandem test at 10МэВ ~ 10% • -peak М4. • Elastic cone slope is in a good agreement with the theoretical predictions BNL-2001

  12. A RIKEN BNL Research Center Workshop A RIKEN BNL Research Center Workshop A RIKEN BNL Research Center Workshop Results with p A RIKEN BNL Research Center Workshop A=0.00203±0.00021 Beam polarization ~20% Sign changed Zero polarization from the source The first nonzero measurement • Statistically significant asymmetry • Right correlation with beam changes • Small systematic errors BNL-2001

  13. 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

  14. 1 6 6 1 15 cm 15 cm 5 2 5 2 3 4 3 4 RHIC year-1 configuration yellowring bluering • 12 Si detectors. • one event per bunch crossing • all channels have independent WFD readout. • zero dead time. Si Preamp. Shaper WFD CAMAC PC 72 72

  15. 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

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

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

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

  19. Test of WFD t Carbon e Fast particles MIPs • 1 WFD module, 4 channels • Common trigger • Everything read to PC • off-line event reconstruction

  20. Polarized Hydrogen Jet Target • pC polarimeter is used as fast relative polarization monitor and was calibrated in AGS at 22 GeV to about 15 %. • Polarized hydrogen jet target allows for absolute beam polarization measurement: • Jet target thickness of 31011 cm-2 achievable(HERMES, PINTEX, NIKHEF) • Jet polarization measurable to better than 3% using Stern-Gerlach method • Collaboration started with Wisconsin, IUCF, and Amsterdam Pol. H jet target at Bates from NIKHEF

  21. Summary • RHIC proton polarimeter successfully tested • Efficient relative and absolute high energy proton polarimetry possible

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