Yousef MakdisiPSTP2011
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
The polarimeters should operate over a very wide range, with beam energy ranging from injection at 24 to 250 GeV
The physics program requires precision polarimetry < 5%
Polarimeter calibration is required at each energy
Beam polarization profile(s)
Polarization lifetime or decay during a store
Polarization measurement on the ramp
Bunch to bunch emittance measurements
The RHIC Polarized Collider
ANDY
STAR
PHENIX
AGS
LINAC BOOSTERPol. H- Source
Spin Rotators(longitudinal polarization)
Siberian Snakes
200 MeV Polarimeter
RHIC pC PolarimetersAbsolute Polarimeter (H jet)
AGS pC PolarimeterStrong 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
polarizedp beam
scattered
proton
NN
NN
targetNtarget
beamNbeam
PA
PA
targettarget
beambeam PP
For p-p elastic scattering only:
elastic kinematics are fully constrained by the recoils only !0.001 < |t| < 0.02 (GeV/c)2
recoilproton or carbon
The RHIC Polarimeters At A Glance
H-Jet polarimeter p-C polarimeter
Target Polarized 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
operation continuously 1 minutes every few hours
AN Measured precisely BRP gives self-calibration
Requires calibration from the Jet data
Role Absolute 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 CalibrationFitting Error < 0.01%
~50keV/ch
ADC [ch]
11
3344
55
66
22
Alpha source
5.486 MeV (85%)
5.443 MeV (12%)
E
Detector port (inner view)Detector port (inner view)
SSDSSD
2mm pitch 12 strips2mm pitch 12 strips
Ultra thin Carbon ribbon Target(5g/cm2)
10mm10mm
Energy Correction
Target
L
T Tdeposit T(x)(adcC) (effective dead layer)
(t0,x)Kinematic Fit(t0,x)Kinematic Fit
Tdeposit T(x) 1
2M
L2
tmeas t0 2
Run5: 40-55 g/cm2
Run6: 70-80 g/cm2
Run8: 75-90 g/cm2
Run9: 50-80 g/cm2
Run 11: 60-65g/cm2
10 g/cm2 6% in AN
Online Polarimeter display
Carbon rate 50 - 100 kHz/ stripPrompts 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
pC Scan the Carbon target over the beam:
Target Position
Inte
nsity
Pola
rizati
on2
2
P
IR
I
P
2. Obtain R directly from the P(I) fit:
€
P(x) = Pmax ⋅ exp −x 2
2σ P2
⎛
⎝ ⎜
⎞
⎠ ⎟
2
2
max 2exp)(
I
xIxI
R
L
LPP
maxmax
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=0.290.07
The Polarized H-Jet Target
separationmagnets(sextupoles)
H2 dissociatorRF cavity
focusingmagnets(sextupoles)
RF transitions
Holding field magnet
recoil detectorsToF, EREC; REC
record beam intensity100% eff. RF transitionsfocusing high intensityB-R polarimeter
Ptarget ~ 0.924 ± 0.018
OR
P+ OR P-
H = p+ + e-
Atomic Beam Source
Scattering chamber
Breit-Rabi Polarimeter
Ion Gage
Ch#1
source for energy calibration 241Am(5.486 MeV)
Recoil Spectrometer Measurement H. Okada
proton beam
Forward scatteredproton
proton target recoil proton
Array of Si detectors measures TR & tof of recoil particles. Channel # corresponds to recoil angle R.2 correlations (TR & tof ) and (TR & R ) the elastic process
Ch#2Ch#3Ch#4Ch#5Ch#6Ch#7Ch#8Ch#9Ch#10Ch#11,12Ch#13Ch#14Ch#15Ch#16Ch#1-16€
t = pout − pin( )2
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 machinebeam-beam requirements
• Backgrounds were minimal no grater than one Beam condition
• Simultaneously measured AN 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 AN 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%
• 2011• 2009
Results Run 11 (Jet contamination??)• A Recoil Energy Cut to test for pion contamination or dilution if any:
At 5 MeV (nominal)
Blue : 0.480 +/- .0053Yellow: 0.479 +/- 0053
At 4 MeV
Blue : 0.484 +/- .0056Yellow : 0.482 +/- .0057
At 3 MeV
Blue: 0.486 +/- .0064Yellow : 0.476 +/- .0066
pp elastic p, p+mπ p,p+2mπp,p+2mπ
Results RUN 11 Polarimeters (Cont’d)
24 GeV 250 GeV
Results Run 11 (Cont’d)
Polarization Loss over the fill (Jet data)
Longitudinal Profiles (Jet data 2 nsec bins)
Polarized Hjet: AN
Weak (if any) energy dependence pp elastic scattering in CNI region is ideal for polarimetry in wide beam energy range
pp-CNIUsed for polarization
measurements
24 GeV: PRD 79, 094014(2009)31 GeV: Preliminary100 GeV: PLB 638 (2006) 450250 GeV: Preliminary
Possibly an unpolarized hydrogen Jet for higher intensity?
p-Carbon: AN
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-CNIUsed for polarization measurements
10% normalization uncertainty not includedPoint-to-point syst. uncertainty under study
A Path Forward (polarimeters)
With the rate dependence issues solved. We look towards more stability and reliability of our operational stability
Complete analysis of the 1 mm Hamamatsu strip detectors We also have 1 mm BNL fabricated silicon and will assess suitability
Smaller acceptance per strip to ameliorate the rate issues as the accelerator strives to higher bunch intensities
Look into commercial WFD systems Stream line and speed up the DAQ system, reduce the impact on the
experiments Continue to improve target production QA
Better Slow Controls, calibration, and monitoring Utilize scintillation counters to get a handle on T0
and dead layer evaluation Add Gadolinium sources 3.27 MeV alpha, better energy calibration
A Path Forward (Jet Target)
Install Hamamatsu 300 (3mmx30mmx16) Silicon Photodiode PIN detectors on two of the six Jet detectors
Use the same amplifier / shaper and WFD readout In situ comparison with the current Hamamatsu Jet
detectors: Energy resolution and thus lower t reach Susceptibility to beam induced background Evaluate any difference in radiation damage
Longer Term redesign the Jet detector flanges to
increase the acceptance by a factor of 2 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
We have in hand several data runs with high rate and the nominal WFD readout We have taken special measurements to study rate problems varying:
The beam intensity and number of bunches The polarimeter target thickness
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:
The preamplifier The shaper With BNL and Hamamatsu detectors With the Yale WFD readout in a full waveform mode to study baseline shifts With a separate ADC and TDC readout
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
0
0.002
0.004
0.006
0.008
0.01
0.012
20 40 60 80 100 120 140 160 180 200 220 240
Beam Energy [GeV]
Asym
metr
y
d
Resonance around 138 GeV
Two such examples:
For the AGS where we sum overMany passes to accumulate statisticsIn this case ramped up and down
For RHIC @ 250 GeV ramp were each is a single pass limited by the onboard local memory
preliminar
y
2005 Jet Normalization Summary
Blue
YellowP(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( 1.01 +/- .031 +/- .029 +/- .005)
P/P(profile)=4.0%
A_N(05)=A_N(04)x( 1.02 +/- .028 +/- .029 +/- .022)
P/P(profile)=4.1%
Goal:10%
pp analyzing power
APEX Rate Studies
Injected Generator pulseNo target
With a thin Carbon targetCarbon rate 42 kHz/ strip
With a thick targetCarbon rate 157 kHz/strip
No appreciable change observed
Rate dependence for 0.6 MeV C: For comparison rate at RHIC 50-100 kHz/ strip
New Detector Tests Atoian, Gill, Morozov
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
A factor of ~2 better resolution (21 KeV vs. 43 KeV) which allows us to measure elastic carbons at ~ t=-0.005 GeV/c2 at higher analyzing power
~ 20 times less bias current after 4 months working on the RHIC beam (0.23A vs. 4 A)
Simplify the readout electronics as well as DAQ
