Polarized beams in RHICA.Zelenski, BNL

PSTP 2011, September 12, St.Petersburg

RHIC High-Luminosity (Polarized) Hadron Collider.

2010-100 ,31, 19.5,3.9, 5.5 GeV

RHIC: the “Polarized” Collider

STARPHENIX

AGS, 24GeVLINAC

BOOSTER, 2.5 GeV

Pol. H- ion source

Spin Rotators

20% Snake

Siberian Snakes

200 MeV polarimeter

RHIC pC “CNI” polarimeters

RHIC

Absolute H-jetpolarimeter

Design goal - 70% Polarization L max = 1.6 1032 s-1cm-2 50 < √s < 500 GeV

AGS pC “CNI” polarimeter

5% Snake

Polarization facilities at RHIC.Polarization facilities at RHIC.

Optically-Pumped Polarized H- Ion Source (OPPIS) at RHIC,(originally developed in collaboration between KEK, BNL,

TRIUMF and INR Moscow).

Optically-Pumped Polarized H- Ion Source (OPPIS) at RHIC,(originally developed in collaboration between KEK, BNL,

TRIUMF and INR Moscow).

RHIC OPPIS produces reliably 0.5-1.0mA(maximum 1.6 mA) polarized H- ion current.Pulse duration 400 us.Polarization at 200 MeV P = 85-90%.

Beam intensity (ion/pulse)

routine operation:Source - 1012 H-/pulseLinac (200MeV) - 5∙1011

AGS - 1.7∙1011

RHIC - 1.4∙1011

(protons/bunch).A beam intensity greatly exceeds RHIC limit, which allowed strong beam collimation in the Booster, to reduce longitudinal and transverse beam emittances.

Schematic Layout of the RHIC OPPISSchematic Layout of the RHIC OPPIS

29.2 GHz ECR proton source29.2 GHz ECR proton source

SCS solenoidSCS solenoid

Probelaser

Na-jetIonizer

cell

Na-jetIonizer

cell

Pumpinglaser

CryopumpsCryopumps

Sona-transition

Rb-cellSCS -solenoid

Depopulation Optical Pumping

5S1/2

5P1/2

λ = 795 nm

Circularly

Polarized lig

ht

MJ = -1/2 MJ = +1/2

Spontaneous

decays.

nLJ

~ 100% polarized Rb

atoms!

1.56 eV

W. Happer, Rev. Mod. Phys. 44, 170 (1972)

relaxation

Optical pumping application is limited by available laser wavelenghes!?Recent progress in laser technology is very promising for new applications.

Optical pumping of alkali metals

2S1/2

5/2

3/2

F =5/2

2P1/2

3/2

8Li I = 2

Li 671 nmNa 590 K 770 Rb 795 Cs 894 Fr 817

Typical polarization = 60 – 70%

381 MHz

mF-5/2 -3/2 -1/2 1/2 3/2 5/2

Valence electron absorbs light tranfers polarization to nucleus via hyperfine coupling

Collinear Optical Pumping polarizer at TRIUMF

Faraday rotation polarimeter of Rb vapor.Faraday rotation polarimeter of Rb vapor.

Θp-optical pumping –on.Θ0-optical pumping -off.

PD1

PD1=I0 sin θp

PD2=I0 cos θp

PRb= (θp- θ0)/ θ0

PD2

Cr:LISAF pumping laser at795 nm

Rb-cell

λ/2

Linear polarized probe laser beam at 780 nm.

Polarized H- ion current pulse out of 200 MeV linac.

Polarized H- ion current pulse out of 200 MeV linac.

Faradey rotation polarization sinal.

500 uA cuurentAt 200 MeV.85-hole ECRSource for themaximum polarization.

400 uS 12·1011 -polarized H- /pulse.

EBIS ionizer for polarized 3He gas (proposal).EBIS ionizer for polarized 3He gas (proposal).

He(2S)→He(1S)

He(2S)→He(1S)

He-3 metastability-exchange polarized cell

P - 80-90%.

Pumping laser 1083 nm.

Pumping laser 1083 nm.

EBIS-ionizer,

B~ 50 kG

EBIS-ionizer,

B~ 50 kG

RFQ

Linac

Booster

AGS

RHIC

RFQ

Linac

Booster

AGS

RHIC

He-transfer line.

Valve. ~50·1011

3He /pulse.

2.5·1011 He++/pulse

Polarization by optical pumping Ionization

1.5·1011 He++/pulse

AGS Cold Snake installed.AGS Cold Snake installed.

The two-snake solution provides better spin matching at injection and extraction.

PHENIX and STAR

STAR

STAR:Large acceptance with azimuthal symmetryGood tracking and PIDCentral and forward calorimetry

PHENIX:High rate capabilityHigh granularityGood mass resolution and PIDLimited acceptance

Intermediate bozons W± - can be produced directly in electroweak processes in

collisions of polarized proton beams of √S= 500 GeV energy at RHIC. In this case parity-violating AL can be as large as 50% and spin-correlation can be

used for studies of different flavor quark contribution to the proton spin.

Sea-quarks polarization studies via intermediate boson W± Production at RHIC, √S= 500 GeV.

u

d

u +d W+ , d +u W-

W +

Spinning Proton Spinning Proton

Spinning Quarks or Gluons

Quark, Gluon, Photon,Electron or Neutrino fromW or Z Decay

2013 HP8 Measure flavor-identified q and q contributions to the spin of the proton via the longitudinal-spin asymmetry of W production.

Initial 500 GeV p+p run already demonstrates W reconstruction capabilities in STAR and PHENIX, with only ~10 pb1.

W asymmetry measurements with power to discriminate among antiquark distribution models require ~300 pb1 and >60% polariz’n.

u and d polarizations predicted to be substantially different in many nucleon structure models.

Initial 500 GeV p+p run already demonstrates W reconstruction capabilities in STAR and PHENIX, with only ~10 pb1.

W asymmetry measurements with power to discriminate among antiquark distribution models require ~300 pb1 and >60% polariz’n.

u and d polarizations predicted to be substantially different in many nucleon structure models.

RHIC luminosity in Run-2011

Bunch intensity ~ 1.6 *1011 proton/bunch

Peak luminosity ~1.5*1032 cm2 s

Polarized beam luminosity.

Foundation of the RHIC Spin Physics.

High-intensity polarized proton source.

“Siberian snakes” to preserve polarization.

P-P and P-Carbon CNI polarimeters.

Theoretical “tools”: QCD calculations.

Polarized Proton Polarimetry from the Source to RHIC energies.

A polarimeter has to satisfy the following:

Beam polarization monitor for Physics ( < 5 % )Several samples over a reasonable time period, one fillBeam polarization diagnostic and Machine tuning tool Sample on demand and online, fast/within minutes Low systematic errors.A large dynamic range & Energy independenceLarge analyzing power, large cross section, & low backgroundReasonable Cost.

Unlike electron polarimeters where processes are calculable, proton reactions rely on experimental verification specially at high energies.

Measuring the beam polarization

In accelerators, the stable spin direction is normally vertical (up/down).

We measure using a nuclear reaction in a plane that is perpendicular to the polarization direction.

NL and NR are the number of scatters to the left and right.

A: is the analyzing power of the reaction

The statistical error in the measurement for PA << 1 is

The polarimeter figure of merit (to optimize) is A2

: is the cross section of the reaction

PA

N N

N N

L R

L R

1

PA N NL R

1 1

Polarized beams at RHIC.Polarized beams at RHIC.

OPPIS

LINAC

Booster

AGS

RHIC

1.5-1.7 p/bunch, P ~65-70%

10 10∙ 11(maximum 40 10∙ 11) polarized H- /pulse.

5 10∙ 11 polarized H- /pulse at 200 MeV, P=85-90%

2 10∙ 11 protons /pulse at 2.3 GeV

Figure of merit for the double spin Asymmetry Collisions is ~ P4 ∙L

Polarimetry at RHIC

Faraday rotation polarimeter Lamb-shift polarimeter 200 MeV - absolute polarimeter AGS p-Carbon CNI polarimeter RHIC p-Carbon CNI polarimeter RHIC - absolute H-jet polarimeter Local polarimeters at STAR and PHENIX

SCHEMATIC LAYOUT OF THE RHIC OPPIS.SCHEMATIC LAYOUT OF THE RHIC OPPIS.

29.2 GHz ECR proton source29.2 GHz ECR proton source

SCS solenoidSCS solenoid

Probelaser

Na-jetIonizer

cell

Na-jetIonizer

cell

Pumpinglaser

CryopumpsCryopumps

Correction coil

Sona-shield

Rb-cellSCS -solenoid

Proton Lamb-shift polarimeter .Proton Lamb-shift polarimeter .

H- → H+ → H(2S)

B=575 G

La(10.2eV) -121.6 nm

H(2S)

• N+ =N0(1+P) / 2• N- = N0(1-P) / 2• P=2 (N+-N-)/(N+ +N-)

OPPIS Lamb-shift polarimeter.OPPIS Lamb-shift polarimeter.

He-ionizer cell

Na-cell, spin-filterand L detectorare placed inside thevacuum chamber.

Polarization at Lamb Shift Polarimeter on 2/01/07 @ 10:34:58(blue), 12:14(red) & 11:25(green) (I_ion = 225 A. Sona Collimator Dia. = 12 mm)

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

-6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Set Point (1 = 25 A)

Pol

ariz

atio

n

Polarized injector, 200 MeV linac and injection lines.Polarized injector, 200 MeV linac and injection lines.

OPPIS

200 MeV polarimeter

Polarization direction is adjusted vertically in the 750 keV beamline by the solenoidal spin -

rotator.

Layout of the 200 MeV proton polarimeter, (2010)

16.2 deg

Polarimeters after the 200 MeV Linac

p-Carbon and p-D polarimetersp-Carbon and p-D polarimeters

D-recoil arm

12 deg. Proton arms

Proton-Carbon ElasticScattering at 200 MeV.

Measurements of the cross section and analyzing power

for proton scattering from 12C at 200 MeV.

The blue (green) curves correspond to protons exiting from the ground (4.44-MeV) state.

The black curve represents the sum of the two data sets.

Edward J. Stephenson, 10/22/2009

16.2deg

~40mb/sr

~5mb/sr

~80%

Notes on the Calibration of the 200-MeV Proton Polarization

Ay=99.96+/0.02%

elastic

GEANT calculation of pC polarimeter for 200MeV proton beam

Collimator Absorber

Sc1 Sc2 Sc3

inelastic

Ep=198.7MeV

Ep=194.3MeV

Cu from 0 to 9mm(step by 1mm)

Cu from 0 to 1mm(step by 0.1mm)

Detector and variable absorber setup

for 200 MeV proton beam.

195.6 Mev

200.0 Mev

Counting rate (S1^S2) vs. Cu absorber thickness.

~20

Measured Analyzing Power vs length of absorber.

Ay(pC) =0.62+/-0.02

Measured Analyzing Power vs length of absorber

Cu absorber thickness, mm

Ay(pC) =0.62+/-0.02

Ay(pC) =0.620+/-0.005

LINAC energy measurements.

Energy measurement by calibrated bending magnet in the Linac HEBT.

Comparison with energy measurement in Booster.

Laser stripping.

Energy stability monitoring in the 200 MeV polarimeter.

Counting rate (S1^S2/S3) vs Cu absorber thickness.

200.0 Mev

195.6 Mev

~12

Vertical 16.20 detector

Horizontal 120 detector

Polarization vs current of the spin rotator.

80.85+/-0.09%

80.29+/-0.019%

Summary.

1. Elastic proton-Carbon scattering (at 16.2 deg. angle) is used in a new polarimeter setup. Analyzing power at 200 MeV is 99.35%.

2. The elastic scattering is used for calibration of inclusive 12 deg. polarimeter arm:

3. Rate in 16 deg arms is ~ 10 event/pulse (12 deg ~300);

4. Ratio N(Sc1^Sc2)/N(Sc1^Sc3) is used for the beam energy monitoring.

Ay (pC) =0.620+/-0.005.

Proton-Carbon CNI polarimeters in AGS and RHIC.

October 6-10, 2008 A.S. Belov, A. N. Zelenski, SPIN2008, USA

BRAMS

STARPHENIX

AGSLINAC

BOOSTER

Pol. H- ion source

Spin Rotators

10-20% Snake

Siberian Snakes

200 MeV polarimeter

RHIC pC “CNI” polarimeters

PHOBOS

RHIC

Absolute H-jetpolarimeter

Design goal - 70% Polarization, Lmax = 1.6 1032 s-1cm-2 , 50 √s 500 GeV

AGS pC “CNI” polarimeter

Polarization facilities at RHIC. Polarimeters.Polarization facilities at RHIC. Polarimeters.

5.9% Snake

p-Carbon Polarimetry at RHICp-Carbon Polarimetry at RHIC

Polarized proton Recoil carbon

90º in Lab frame

Carbon target

LL NN or

RR NN or

or

Pbeam N

ANpC

N NL NR

NL NR

Pbeam Required Accuracy ~5%

Pbeam Required Accuracy ~5%

p C

p C

the left – right scattering asymmetry AN arises from the interference of

the spin non-flip amplitude with the spin flip amplitude (Schwinger)

in absence of hadronic spin – flip contributions

AN is exactly calculable (Kopeliovich & Lapidus):

hadronic spin- flip modifies the QED“predictions”

interpreted in terms of Pomeron spin – flip and parametrized as

AN for Coulomb -Nuclear Interference.

AN for Coulomb -Nuclear Interference.

)Im()Im( *2

*1

hadflipnon

hadflip

hadflipnon

emflipN CCA

1)p pphad

Z

ty

y

y

m

ZA

pAtot

pAtotp

N 81

1

82

2/3

2

25 2

1

2

1

2

1II ppp

AN (t)

had

p

had

mt

s 05 )(

Hydrogen Gas Jet and Carbon Wire Targets.

Gas Jet Target Carbon Wire Target

Beam Cross Section

p

FWHM~1.8mmFWHM~1.8mm

Average Pave Peak Ppeak

The target ladder.

New target motion mechanism.

Detector SetupDetector Setup

Ultra thin Carbon ribbon Target(3.5g/cm2)

11

3344

55

66

22

Si strip detectorsSi strip detectors(TOF, E(TOF, ECC))

18cm18cm

10mm10mm

2mm pitch 12 strips2mm pitch 12 strips

72 strips in total72 strips in total

Redundancy

Systematic/Consistency Check

Redundancy

Systematic/Consistency Check

Detector port (inner view)Detector port (inner view)

SSDSSD

Event Selection

Carbon

400<E<900keV

Very clean Carbon event extraction!

3

AN at Coulomb Nuclear Interference (CNI) RegionAN at Coulomb Nuclear Interference (CNI) Region

AN C1 flipem *non flip

had C2non flipem * flip

had

pChad

(p 1)

st ? Reggen/Pomeron

exchange

zero hadronic spin-flip

With hadronic spin-flip (E950)

Phys.Rev.Lett.,89,052302(2002)

pC Analyzing Power

Ebeam = 21.7GeVEbeam = 21.7GeV

(High energy & small t limit)

Ebeam = 100 GeVEbeam = 100 GeV

unpublished

Run04

9%

Polarization measurements in RHIC at 100 GeV.Polarization measurements in RHIC at 100 GeV.

Polarization at 100 GeVin RHIC 60-65%.

May 3, 2011 A. Poblaguev Spin Meeting

APEX measurements

May 3, 2011 A. Poblaguev Spin Meeting 56

• Many measurements during short period of time• No collisions, rotations, etc.• Different targets in the same fill.

Blue 2Vertical Target 63 measurements

Polarization profiles, Run 2011

• Very thin target , practically non-destructive.• Very high rate.• Very good signal/noise ratio. Delayed C-ion

detection.• Single bunch measurements.

• Remaining problems :• Target alignment (Solved).• Carbon strips are not straight. Target lifetime.

P-CNI polarimeter can be an ideal wire-scanner.

P-CNI polarimeter as a wire scanner.

AGS and RHIC CNI polarimeters target mechanisms were upgraded for this Run.

Yellow, Vertical-15pi, Horiz-13 pi

AGS pol., during H-jet meas. at injection

Intensity -1.51.13

A AGS ~ A RHIC injection/ 1.11

Proton polarization measurements in AGS and RHIC at the beam energies 24-250 GeV) are based on Proton-Carbon and Proton-Proton ( H-jet polarimeter) elastic scattering in the Coulomb Nuclear Interference (CNI) region.

The CNI polarimeters are the essential tools for polarized proton acceleration setup and operation and provide polarization values for RHIC experiments.

Polarimeter operation in the scanning mode also gives polarization profile and beam intensity profile (beam emittance) measurements. Bunch by bunch emittance measurements is a very powerful tool for the machine setup.

AGS polarimeter upgrade andTune-jump system in Run2011.

RHIC: the “Polarized” Collider

STARPHENIX

AGS, 24GeVLINAC

BOOSTER, 2.5 GeV

Pol. H- ion source

Spin Rotators

20% Snake

Siberian Snakes

200 MeV polarimeter

RHIC pC “CNI” polarimeters

RHIC

Absolute H-jetpolarimeter

Design goal: P=70%, L max = 1.6 1032 s-1cm-2 50 < √s < 500 GeV

AGS pC “CNI” polarimeter

5% Snake

Polarization facilities at RHIC.Polarization facilities at RHIC.

20% snake

Tune jump system in AGS

72.7%

Polarization measurement in AGS at 24 GeV.Polarization measurement in AGS at 24 GeV.

Polarization out of AGS60-70%

Polarization at injection in RHIC with the Jump-Quads in operation.

16 February 2011 Spin Meeting

AGS CNI Polarimeter 2011

11 February 2011 RHIC Spin Collaboration Meeting 67

1,8 - Hamamatsu, slow preamplifiers

2,3,6,7 - BNL, fast preamplifiers

4,5 - Hamamatsu, fast preamplifiers

3 different detector types:

Run 2009: BNL, slow preamplifiers

Larger length (50 cm)

Regular length (30 cm)

Outer Inner

AGS Horiz. polarization profile , JQ-off time

AGS Horiz. polarization profile , JQ-on

Polarization measurements on the energy ramp in AGS.

Horizontal emittance, AGS intensity-1.5*10^11

Vertical emittance, AGS intensity-1.5*10^11

Absolute H-jet polarimeter in RHIC.

October 6-10, 2008 A.S. Belov, A. N. Zelenski, SPIN2008, USA

Spin filtering technique. Atomic Beam

Sources. Spin filtering technique. Atomic Beam

Sources. Hydrogen atoms with electron polarization: mJ=+1/2 trajectories.

Electron magnetic moment is 659 times Larger than proton : e / P ~659.Focusing strength: ~ (dB/dr) e

RF transition, polarization transfer from electrons to protons

RHIC beam crossing

Breit-Rabi polarimeter

permanent magnetsextupole - 1.7 Tgradient 5.7 T/cm

H-jet polarimeter. H-jet polarimeter.

• The H-jet polarimeter includes three major parts: polarized Atomic Beam source (ABS), scattering chamber, and Breit-Rabi polarimeter.

• The polarimeter axis is vertical and the recoil protons are detected in the horizontal plane.

• The common vacuum system is assembled from nine identical vacuum chambers, which provide nine stages of differential pumping.

• The system building block is a cylindrical vacuum chamber 50 cm in diameter and of 32 cm length with the four 20 cm (8.0”) ID pumping ports.

H-jet dissociator design.H-jet dissociator design.

65 cm

Cooling multifoil copper straps.

Window.

Cold head, 42 K

Fix RHIC proton beam position (diameter ~1mm).

Move H-Jet-target system for every 1.5 mm step.

Recoil detector can detect H-Jet-target !

Using RHIC-beam and Recoil detector

Using 2.0 mm diameter compression tube

Find the best collision point !

target

target

beam

beamN PP

tA

RHIC proton

beam

Forward scatteredproton

H-jet target

recoil proton

PPetargt

beametargtbeam

02 inout ppt

beam

beam

target

target

target

target

beam

beam

P

P

P

P

H-Jet polarimeter.

Ptarget is measured by Breit- Rabi Polarimeter

<5%

Elastic scattering: Interference between electromagnetic and hadronic amplitudes in the Coulumb-Nuclear Interference (CNI) region.

2*Im hadNF

emNF

hadSF

hadNF

emSFNA

RHIC proton beam

H-jet target

IP12

recoil proton

Si detectors (8cm 5cm)3 L-R sides

Strip runs along RHIC beam axis

1ch width = 4mm (400strips)

Channel # relates to recoil angle R, 5 mrad pitch.

Each channel measures kinetic energy TR and TOF.

L = 0.8 m

Ch#1

source for energy calibration 241Am(5.486 MeV)

How to identify elastic events ?

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

Ch# R, R big TR big fast protons 02 inout ppt

R

Ch#1

#16

H-jet is an ideal polarimeter !

• High (~4.5%) analyzing power in a wide energy range (23-250 GeV).

• High event rate due to high intensity (~100 mA) circulated beam current in the storage ring (~6% statistical accuracy in one

8hrs. long fill). High polarized H-jet density in RHIC ABS.• Non-destructive.• No scattering for recoil protons.• Clean elastic scattering event identification.• Straightforward calibration with Breit-Rabi polarimeter.• Most of the false asymmetries are cancelled out in the ratio:

P beam =( 1/A)Beam asym / Target asym

Problem. Polarization dilution by H2, H2O and other residual gases.Largest source of systematic error.

H-Jet polarimeter: AN in pp

2*Im hadNF

emNF

hadSF

hadNF

emSFNA

24 GeV: calculations with no hadronic spin flip amplitude contribution are not consistent with data

100 GeV: calculations with no hadronic spin flip amplitude contribution are consistent with data

More data to come: 24 GeV: take more data in Run9/1031 GeV: finalize analysis of data from Run6250 GeV: take data in Run9/10

target

target

PA pp

N

24 GeV

100 GeVPLB638, 450

Preliminary

250 GeV luminescence In H-jet

Blue vert. IPM measurement-16 pi.

Blue vertical emittance measurement by luminescence monitor in the H-jet polarimeter.

H-jet polarization measurements, Run 2011

Blue- Blue ringRed- Yellow ring

Polarization measurements in RHIC with the H-jet polarimeter.

Polarization measurements in RHIC with the H-jet polarimeter.

PTarget

APP

PB

ApC

PB – beam

polarization

Exp.asymm.(pp)

22-250 GeV beam energy.

± 5% absolute accuracy.

Analyzing power measurement

Exp.asymm.(pC)

Measured to ±1% accuracy by the BRP and background evaluation.

RHIC local polarimeter

BRAHMS

STARPHENIX

AGSLINAC

BOOSTER

Pol. H- ion source

Spin Rotators

10-20% Snake

Siberian Snakes

200 MeV polarimeter

RHIC pC “CNI” polarimeters

PHOBOS

RHIC

Absolute H-jetpolarimeter

AGS pC “CNI” polarimeter

Polarization facilities at RHIC. “Siberian Snakes”Polarization facilities at RHIC. “Siberian Snakes”

5.9% Snake

E.Courant coined the“Siberian Snake” name

PHENIX Local Polarimeter

Utilizes spin dependence of very forward neutron production (PLB650, 325):

neutronchargedparticles

ZDC (energy) + SMD (position)

SMDZDC

PHENIX local polarimeter

PHENIX Local Polarimeter

Blue Yellow

Blue Yellow

Blue Yellow

Spin Rotators OFFVertical polarization

Spin Rotators ONCorrect Current !Longitudinal polarization!

Spin Rotators ONCurrent ReversedRadial polarization

Asymmetry vs φ

Monitors spin direction in PHENIX collision region

STAR Local Polarimeter

3.3<||< 5.0 (small tiles only)

Utilizes spin dependence of hadron production at high xF:

Bunch-by-bunch (relative) polarization

Monitors spin direction in STAR collision regionCapable to precisely monitor polarization vs time in a fill, and bunch-by-bunch

Summary of RHIC polarimetry

Source, Linac, AGS-injector polarimetrs.Hjet:

Absolute polarization measurements Absolute normalization for other RHIC Polarimeters

pC: Separate for blue and yellow beamsNormalization from HJetPolarization vs. time in a fillPolarization profileFill-by-fill polarizations for experiments

PHENIX and STAR Local Polarimeters: Monitor spin direction (through transverse spin component) at collisionPolarization vs time in a fill (for trans. pol. beams)Polarization vs bunch (for trans. pol. beams)