Yousef Makdisi PSTP2011 September 12-18, 2011 Proton Polarimetry at the Relativistic Heavy Ion Collider and Future Upgrades Yousef I. Makdisi Brookhaven National Laboratory For The RHIC Polarimetry Group I. Alekseev, E. Aschenauer, G. Atoian, A. Bazilevsky, A. Dion, H. Huang, A. Poblaguev, W. Schmidke, D. Smirnov, D. Svirida, K. Yip, A. Zelenski * Run 11 analyses: Dion, Poblaguev, Schmidke, Smirnov

Outline Requirements for the physics program and machine development The p-Carbon CNI polarimeters and Jet for Run 11 The operation in Run 11 The p-C polarimeters The Polarized Jet target The Results The path forward

The Polarimetry Requirements for RHIC l The polarimeters should operate over a very wide range, with beam energy ranging from injection at 24 to 250 GeV l The physics program requires precision polarimetry < 5% l Polarimeter calibration is required at each energy l Beam polarization profile(s) l Polarization lifetime or decay during a store l Polarization measurement on the ramp l Bunch to bunch emittance measurements

The RHIC Polarized Collider A N DY STAR PHENIX AGS LINAC BOOSTER Pol. H - Source Spin Rotators (longitudinal polarization) Siberian Snakes 200 MeV Polarimeter RHIC pC Polarimeters Absolute Polarimeter (H  jet) AGS pC Polarimeter Strong AGS Snake Helical Partial Siberian Snake Spin Rotators (longitudinal polarization) Siberian Snakes E-Lens and Spin Flipper EBIS

pp and p-Carbon Elastic Scattering recoil p polarized p beam scattered proton For p-p elastic scattering only: elastic kinematics are fully constrained by the recoils only ! < |t| < 0.02 (GeV/c) 2 recoil proton or carbon

The RHIC Polarimeters At A Glance H-Jet polarimeterp-C polarimeter TargetPolarized atomic hydrogen gas jet target Ultra thin carbon ribbon Event rate~20 Hz 8% statistics in a 6-hr fill ~2M Hz 2-3% per measurement operationcontinuously1 minutes every few hours ANAN Measured precisely BRP gives self-calibration Requires calibration from the Jet data RoleAbsolute beam pol. measurement, Calibration for RHIC pC polarimeter ONLINE monitor, Fill by Fill beam polarization Polarization Profiles Beam Emittance measurements

RHIC Polarimeters Layout

p-Carbon Polarimeters Energy Calibration Fitting Error < 0.01% ~50keV/ch ADC [ch] Alpha source MeV (85%) MeV (12%) EE Detector port (inner view) SSD 2mm pitch 12 strips Ultra thin Carbon ribbon Target (5  g/cm 2 ) 10mm

Energy Correction Target L (adc  C  ) (effective dead layer) (t 0,  x )  Kinematic Fit Run5:  g/cm 2 Run6:  g/cm 2 Run8:  g/cm 2 Run9:  g/cm 2 Run 11:  g/cm 2 10  g/cm 2 6% in  A N

Online Polarimeter display Carbon rate kHz/ strip Prompts background to signal ~ 1/1 with an energy threshold cut at 125 keV. Shaper pulse rise time 20 nsec and fall time 50 nsec

pC: Polarization Profile pCScan the Carbon target over the beam: Target Position Intensity Polarization II PP 2. Obtain R directly from the P(I) fit:   I P Precise target positioning is NOT necessary 1. Directly measure  I and  P : R ~ 0.1–0.3  5–15% difference in lower polarization seen by HJet compared to that observed by experiments R=0.29  0.07

The Polarized H-Jet Target separation magnets (sextupoles) H 2 dissociator RF cavity focusing magnets (sextupoles) RF transitions Holding field magnet recoil detectors ToF, E REC ;  REC record beam intensity 100% eff. RF transitions focusing high intensity B-R polarimeter P target ~ ± OR P + OR P - H = p + + e - Atomic Beam Source Scattering chamber Breit-Rabi Polarimeter Ion Gage

Ch#1  source for energy calibration 241 Am(5.486 MeV) Recoil Spectrometer Measurement H. Okada proton beam Forward scattered proton proton target recoil proton Array of Si detectors measures T R & tof of recoil particles. Channel # corresponds to recoil angle  R. 2 correlations (T R & tof ) and (T R &  R )  the elastic process Ch#2Ch#3 Ch#4Ch#5 Ch#6 Ch#7Ch#8 Ch#9 Ch#10 Ch#11,12 Ch#13 Ch#14Ch#15 Ch#16 Ch#1-16 RR Ch#1 #16

Operational Problems Run 11 Jet: The Jet had a mishap early in the run where enough dissociator RF power was dumped to cause significant damage to the nozzle Since, were not able to run the intensity at the prescribed pattern, namely high to start and slowly depletes over the period of two weeks. Instead we reverted to more frequent nozzle cleaning (more downtime) We also lost our usual number of turbo pumps Polarimeters: The idea of running the downstream polarimeters readout inside the tunnel did not work as we faced frequent downtime to what appears as single event upset to the electronics. No long term radiation damage was seen as the equipment was moved outside We did experience unusual target losses in one polarimeter which was attributed to one mechanical drive

Running conditions Run 11 Ran with two beam simultaneously separated vertically by 3-4 mm dictated by the machine beam-beam requirements Backgrounds were minimal no grater than one Beam condition Simultaneously measured A N in pp elastic Scattering at the specified energy and beam Polarization Ran at both 250 GeV and injection 24 GeV

Results Run 11 Measured the Analyzing Power in pp elastic scattering to assure all is fine Used the average A N to normalize the beam asymmetry for each fill. Note the jet beam is 6 mm FWHM sees the full beam profile Averaged over the Run: Blue Beam Polarization ~ 48% Yellow Beam Polarization ~ 48%

Results Run 11 (Jet contamination??) A Recoil Energy Cut to test for pion contamination or dilution if any: At 5 MeV (nominal) Blue : / Yellow: / At 4 MeV Blue : / Yellow : / At 3 MeV Blue: / Yellow : / pp elasticp, p+m π p,p+2m π

Results RUN 11 Polarimeters (Cont’d) 24 GeV250 GeV

Results Run 11 (Cont’d) Polarization Loss over the fill (Jet data) Polarization Longitudinal Profiles (Jet data 2 nsec bins)

Polarized Hjet: A N Weak (if any) energy dependence  pp elastic scattering in CNI region is ideal for polarimetry in wide beam energy range pp-CNI Used for polarization measurements 24 GeV: PRD 79, (2009) 31 GeV: Preliminary 100 GeV: PLB 638 (2006) GeV: Preliminary Possibly an unpolarized hydrogen Jet for higher intensity?

p-Carbon: A N 31 GeV 100 GeV  250 GeV Weak energy dependence  pC elastic scattering in CNI region is good for polarimetry in wide beam energy range pC-CNI Used for polarization measurements  10% normalization uncertainty not included Point-to-point syst. uncertainty under study

A Path Forward (polarimeters) l With the rate dependence issues solved. We look towards more stability and reliability of our operational stability l Complete analysis of the 1 mm Hamamatsu strip detectors l We also have 1 mm BNL fabricated silicon and will assess suitability n Smaller acceptance per strip to ameliorate the rate issues as the accelerator strives to higher bunch intensities l Look into commercial WFD systems l Stream line and speed up the DAQ system, reduce the impact on the experiments l Continue to improve target production QA l Better Slow Controls, calibration, and monitoring l Utilize scintillation counters to get a handle on T 0 and dead layer evaluation l Add Gadolinium sources 3.27 MeV alpha, better energy calibration

A Path Forward (Jet Target) l Install Hamamatsu 300  (3mmx30mmx16) Silicon Photodiode PIN detectors on two of the six Jet detectors l Use the same amplifier / shaper and WFD readout l In situ comparison with the current Hamamatsu Jet detectors: n Energy resolution and thus lower t reach n Susceptibility to beam induced background n Evaluate any difference in radiation damage l Longer Term redesign the Jet detector flanges to increase the acceptance by a factor of 2 l Need a better handle on the Jet systematics. 45x50mm, 4x12=48 strips (4mm by 50+50=100mm)

Summary A new RHIC polarimetry group is on board and had a busy year The AGS rate studies resulted in installation of current sensitive amplifiers in the RHIC polarimeters and resolved the rate problem for now. No significant increase in noise either. We experienced a more stable running environment The readout inside the RHIC tunnel did not pan out due to disruption from possible single event upset problems >> reverted to the out side Complementary local polarimeters are employed at the experiments ZDC (inclusive neutron asymmetry) and beam – beam counter types) Towards He3 polarimetry a Workshop at BNL Sept 28-30, 2011

Backup

Rate Studies Atoian, Bazilevsky, Gill, Morozov, Rescia l We have in hand several data runs with high rate and the nominal WFD readout l We have taken special measurements to study rate problems varying: l The beam intensity and number of bunches l The polarimeter target thickness l With help from the Instrumentation Division also used a fast scope (20 G samples/sec) to study the pulse height and baseline variation versus rate at the output of various stages: l The preamplifier l The shaper l With BNL and Hamamatsu detectors l With the Yale WFD readout in a full waveform mode to study baseline shifts l With a separate ADC and TDC readout l Analyses are ongoing but seem to indicate that both the BNL and Hamamtsu detectors can handle the high rates through the shaper stage.

Polarimeters problems C-rate Pulser rate Pulser amp. Pulser time

Polarization On The Ramp Resonance around 138 GeV Two such examples: For the AGS where we sum over Many passes to accumulate statistics In this case ramped up and down For 250 GeV ramp were each is a single pass limited by the onboard local memory prelimin ary

2005 Jet Normalization Summary l Blue l Yellow  P(blue)/P(blue) = 5.9%  P(yellow)/P(yellow) = 6.2%  [P(blue) x P(yellow) ]/[P_b x P_y] = 9.4% A_N(2005) = A_N(2004) x (S +/-  A(jet stat)/A +/-  A(jet syst)/A +/-  A(pC syst)/A) A_N(05)=A_N(04)x( / / /-.005)  P/P(profile)=4.0% A_N(05)=A_N(04)x( / / /-.022)  P/P(profile)=4.1% Goal: 10%

pp analyzing power

APEX Rate Studies Injected Generator pulse No target With a thin Carbon target Carbon rate 42 kHz/ strip With a thick target Carbon rate 157 kHz/strip No appreciable change observed

Rate dependence for 0.6 MeV C: For comparison rate at RHIC kHz/ strip

New Detector Tests Atoian, Gill, Morozov l Compare BNL and Hamamatsu large area (1cm x 1cm) Si and strip PIN photodiode detectors. Results show a several advantages to use these devices instead of the strip detectors l A factor of ~2 better resolution (21 KeV vs. 43 KeV) which allows us to measure elastic carbons at ~ t= GeV/c 2 at higher analyzing power l ~ 20 times less bias current after 4 months working on the RHIC beam (0.23  A vs. 4  A) l Simplify the readout electronics as well as DAQ