Transcript Current and Future Transverse Spin at PHENIX

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
Yousef Makdisi
PSTP2011
September 12-18, 2011
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
RHIC pC Polarimeters
Absolute Polarimeter (H jet)
ANDY
E-Lens and Spin Flipper
Siberian Snakes
Siberian Snakes
PHENIX
STAR
Spin Rotators
(longitudinal polarization)
Spin Rotators
(longitudinal polarization)
Pol. H Source
LINAC
BOOSTER
EBIS
Helical Partial Siberian Snake
200 MeV Polarimeter
AGS
AGS pC Polarimeter
Strong AGS Snake
pp and p-Carbon Elastic Scattering
elastic kinematics are fully constrained by the recoils only !
0.001 < |t| < 0.02 (GeV/c)2
scattered
proton
polarized
p beam
recoil
proton or
carbon
recoil p
For p-p elastic scattering only:
NN

NN
 beam  AN  Pbeam
 target   AN  Ptarget
 beam
Pbeam  
 Ptarget
 target
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
• Two polarimeters in each beam (redundancy)
• A pair of polarimeters readout inside the tunnel (an
attempt to reduce dispersion through the long 70m cables)
• After tests in the AGS replaced charge sensitive
amplifiers with fast current sensitive amplifiers for all
• Target holders 6 (V) 6 (H) in each polarimeter
• Simultaneous H and V pol. Profiles
• In situ test of new detectors
• Multiplexing to reduce cost
p-Carbon Polarimeters Energy Calibration
Ultra thin Carbon
ribbon Target
(5m g/cm2)
6
5
4
Fitting Error < 0.01%
1
2
Alpha source
5.486 MeV (85%)
5.443 MeV (12%)
3
E
ADC [ch]
~50keV/ch
2mm pitch 12 strips
Detector port (inner view)
SSD
10mm
Energy Correction
2
1
L
T


T
(

x
)

M 2
de
p
osit
2
t

t


me
0
as
L

Target
(t0,x)Kinematic Fit
Run5: 40-55 mg/cm2
T

T


T
(

x
) Run6: 70-80 mg/cm2
deposit
2
(adcC) (effective dead layer) Run8: 75-90 mg/cm
Run9: 50-80 mg/cm2
Run 11: 60-65mg/cm2

10 mg/cm2
6% in AN
Online Polarimeter display
Carbon rate 50 - 100 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
1. Directly measure I and P :
Intensity
Scan the Carbon target over the beam:
I
 I2
R 2
P
2. Obtain R directly from the P(I) fit:
I
 x 2 
P(x)  Pmax  exp 2 
 2P 
 x 
I ( x)  I max  exp   2 
 2 I 
2
Polarization
pC

P
P



P  Pmax
 L
 
 Lmax



R
R=0.290.07
Target Position
Precise target positioning is NOT necessary
R ~ 0.1–0.3  5–15% difference in lower
polarization seen by HJet compared to that observed by experiments
The Polarized H-Jet Target
H = p+ + e-
separation
magnets
(sextupoles)
focusing
magnets
(sextupoles)
OR
P+ OR
H2 dissociator
RF cavity
Atomic
Beam
Source
RF transitions
P-
record beam intensity
100% eff. RF transitions
focusing high intensity
B-R polarimeter
Holding field
magnet
recoil detectors
ToF, EREC; QREC
Scattering
chamber
Breit-Rabi
Polarimeter
Ptarget ~ 0.924 ± 0.018
Ion Gage
Recoil Spectrometer Measurement
H. Okada
Forward scattered
proton
proton beam
t  pout  pin 
2
proton
target recoil proton
Ch#1
Ch#3
Ch#2
Ch#15
Ch#14
Ch#9
Ch#6
Ch#11,12
Ch#13
Ch#16
Ch#8
Ch#7
Ch#5
Ch#4
Ch#10
Ch#1-16

 source for
energy calibration
241Am(5.486 MeV)
R
#16
Ch#1
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
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 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 +/- .0053
Yellow: 0.479 +/- 0053
At 4 MeV
Blue : 0.484 +/- .0056
Yellow : 0.482 +/- .0057
At 3 MeV
Blue: 0.486 +/- .0064
Yellow : 0.476 +/- .0066
pp elastic
p, p+mπ
p,p+2mπ
Results RUN 11 Polarimeters (Cont’d)
24 GeV
250 GeV
Results Run 11 (Cont’d)
Polarization
Longitudinal Profiles (Jet data 2 nsec bins)
Polarization Loss over the fill (Jet data)
Polarized Hjet: AN
Used for
polarization
measurements
pp-CNI
Weak (if any) energy
dependence 
pp elastic scattering in
CNI region is ideal for
polarimetry in wide
beam energy range
24 GeV: PRD 79, 094014(2009)
31 GeV: Preliminary
100 GeV: PLB 638 (2006) 450
250 GeV: Preliminary
Possibly an unpolarized hydrogen Jet for higher intensity?
p-Carbon: AN
Used for polarization
measurements
pC-CNI
 31 GeV
 100 GeV
 250 GeV
10% normalization uncertainty
not included
Point-to-point syst. uncertainty
under study
Weak energy
dependence 
pC elastic scattering in
CNI region is good for
polarimetry in wide
beam energy range
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 300m (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
Two such examples:
For the AGS where we sum over
Many passes to accumulate statistics
In this case ramped up and down
Resonance around 138 GeV
0.012
0.01
Asymmetry
For RHIC @ 250 GeV ramp were
each is a single pass limited by the
onboard local memory
0.008
0.006
d
0.004
0.002
0
20
40
60
80
100
120
140
160
Beam Energy [GeV]
180
200
220
240
2005 Jet Normalization Summary
A_N(2005) = A_N(2004) x (S +/- A(jet stat)/A
+/- A(jet syst)/A +/- A(pC syst)/A)

Blue
A_N(05)=A_N(04)x( 1.01 +/- .031 +/- .029 +/- .005)
P/P(profile)=4.0%

P(blue)/P(blue) = 5.9%
Yellow
A_N(05)=A_N(04)x( 1.02 +/- .028 +/- .029 +/- .022)
P/P(profile)=4.1%
P(yellow)/P(yellow) = 6.2%
[P(blue) x P(yellow) ]/[P_b x P_y] = 9.4%
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 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
(0.23mA vs. 4 m A)
Simplify the readout electronics as well as DAQ