E.C. Aschenauer Varenna, July 20112 Large scientific instruments that produce and accelerate subatomic particles and ‘smashes them’ Fixed target

Lecture IRHIC

The Relativistic Heavy Ion Collider

Varenna, July 2011 2

Particle accelerators

E.C. Aschenauer

Large scientific instruments that produce and accelerate subatomic particles and ‘smashes them’

Fixed target

Collider

Particles: electrons, positrons, protons, anti-protons, ions…..(atoms stripped of electrons: nuclei)

Nuclei protons + neutrons quarks + gluons


RHIC @ Brookhaven National Lab

E.C. Aschenauer

RHIC

NSRLLINAC

Booster

AGS

Tandems

STAR6:00 o’clock

PHENIX8:00 o’clock

Jet/C-Polarimeters12:00 o’clock

RF4:00 o’clock

EBIS

ERL Test Facility

ANDY2:00 o’clock

What do we collide ?

p

Polarized light ions He3 16 - 166 GeV/u

Light ions (d,Si,Cu)Heavy ions (Au,U)5-100 GeV/u

Polarized protons24-250 GeV

1st Collisions: 13/06/2000


STAR

PHENIX

AGS

LINACBOOSTER

Pol. Proton Source500 mA, 300 ms

Spin Rotators

Partial Siberian Snake

Siberian Snakes

200 MeV Polarimeter AGS Internal Polarimeter

Rf Dipoles

RHIC pC PolarimetersAbsolute Polarimeter (H jet)

AGS pC Polarimeters

Strong AGS Snake

MP6 MP7

Tandem Van der Graaf

Stripping Au 77+ to 79+

1 MeV/u32+

9 GeV/u77+

100 GeV/u79+

The RHIC Complex

E.C. Aschenauer

ANDY


BoosterRing

AGS

Switchyard

RHIC

TandemVan de Graaff

The RHIC Accelerator System

E.C. Aschenauer

Blue Ring

Yellow Ring


What does RHIC do?

E.C. Aschenauer

RHIC accelerates gold nuclei in two

beams to about 100 GeV/nucleon each

(i.e., to kinetic energies that are over

100 times their rest mass-energy)and brings these beams into a200 GeV/nucleon collision.

RHIC accelerates polarized protonsup to 250 GeV and brings them intoup to 500 GeV collision

Three experiments, STAR,PHENIX, and ANDY study these collisions.


The RHIC project chronology

E.C. Aschenauer

1989 RHIC design 1991 construction starts 1996 commissioning AtR injection lines 1997 sextant test (1/6 of the ring) 1999 RHIC engineering/test run 2000 first collisions 2001-02 Au-Au run, polarized p run 2003 deuteron-Au run, pp 2004 Au-Au physics run and 5 weeks pp development 2005 …..RHIC is also a giant engineering challenge: magnets (3000+ industry and lab built superconducting

magnets)cryogenics (2 weeks to cool down to

4.2K) ,instrumentation, etc.


RHIC operations

The operation of RHIC and its injectors is a rather challenging endeavor….

RHIC operates for ~5-6 months/year – 24h/day 7 days/weekRHIC Shutdown 6-7 months, for machine improvements

(other programs are run by the injectors, Tandem delivering ions for industrial R&D, Booster delivering ions for NASA experiments, etc.)

CONTROL ROOM : remote access to instrumentations and controls

Accelerator physicists, shift leaders (machine initial set-up, new developments, beam experiments)

Operations group: operation coordinator, operators (“routine’ operations, shifts 1 OC + 2 operators)

Technical support (engineers and technicians on call and/or site for system diagnosis and trouble-shooting)

E.C. Aschenauer


Beamintensities

Pilotbunch

injection

accelerationpreparation

collisionsSet-up

Store(collisions)

time

Startacceleration

transition

Beta*squeeze

coggingre-bucketingcollimationsteering

collisions

inject, accelerate, collide......!

E.C. Aschenauer


A day in the life of RHIC…

E.C. Aschenauer


designluminosity

Week 9 Feb to 17 Feb [66% of calendar time in store]

enhancedluminosity

60x109Auintensity

Beam

exp

eri

men

ts

A week in the life of RHIC…

E.C. Aschenauer


A few years in the life of RHIC…

E.C. Aschenauer

Polarized proton runs

Operated modes (beam energies):Au–Au 3.8/4.6/5.8/10/14/32/65/100 GeV/nd–Au* 100 GeV/n Cu–Cu 11/31/100 GeV/np–p 11/31/100, 250 GeV Planned or possible future modes:Au – Au 2.5 GeV/n (~ SPS cm energy)U – U 100 GeV/np – Au* 100 GeV/nCu – Au* 100 GeV/n (*asymmetric rigidity)

Achieved peak luminosities (100 GeV, nucl.-pair):Au–Au 1951030 cm-2 s -1

p–p 601030 cm-2 s -1

Other large hadron colliders (scaled to 100 GeV):Tevatron (p – pbar) 431030 cm-2 s -1

LHC (p – p) 371030 cm-2 s -1

13

AnDY in Run-11 (250 GeV pp)

E.C. Aschenauer Varenna, July 2011

Beam envelope function b* = 3.0 m at IP2 Reduced IP2 crossing angle from initially 2.0 mrad to zero Added 3rd collision with following criteria (last instruction):

1. Nb ≤ 1.5x1011

2. Beam loss rate <15%/h in both beams3. Not before first polarization measurement 3h into store

PHENIX

STAR

AnDY

small impact visible impact,few percent loss to STAR/PHENIX

loss rates

x/IP = 0.004

x/IP = 0.005


ANDY an getting Lumi

~2mr crossing angle

~1.6mr crossing angle

~0mr crossing angle

systematically increased thresholds

for IP2 collisions

ANDY got ~ 6.5/pb

in run11 with b*=3m

E.C. Aschenauer

15

Future operation of AnDY

E.C. Aschenauer Varenna, July 2011

Can reduce b* at IP2have run with b* = 2.0 m previously for BRAHMSb* = 1.5 m probably ok, needs to be tested

Longer stores 10h instead of 8h in Run-11 (depends on luminosity lifetime and

store-to-store time) Collide earlier in store when conditions are met

needs coordination with polarization measurement, PHENIX and STAR

Electron lenses (see later) if AnDY runs beyond Run-13 increases max beam-beam tune spread, currently DQmax,bb ≈ 0.015 can be used for to increase x~Nb/e and/or number of collisions

Run-11 luminosity at AnDY: max ~0.5 pb-1/store

With improvements: ~3x increase, ~10 pb-1/week (max)

pp in Run-4 (100 GeV)

Varenna, July 2011 16E.C. Aschenauer

Polarized proton beamsOr

How to do magic with an accelerator


What is Spin? From Google…

revolve quickly and repeatedly around one's own axis, "The dervishes whirl around and around without getting dizzy”

twist and turn so as to give an intended interpretation, "The President's spokesmen had to spin the story to make it less embarrassing”

a distinctive interpretation (especially as used by politicians to sway public opinion), "the campaign put a favorable spin on the story"

E.C. Aschenauer


What is Spin?

Classical definition the body rotation around its own axis

Particle spin: an intrinsic property, like mass and charge a quantum degree freedom associated with the intrinsic

magnetic moment.

G: anomalous gyromagnetic factor, describes the particle internal structure. For particles:

point-like: G=0 electron: G=0.00115965219 muon: G=0.001165923 proton: G=1.7928474

m: particle mass

q: electrical charge of particle

μ

s=(1 + G)

q

mS

E.C. Aschenauer


Spin: single particle pure spin state aligned along a quantization axis

Spin vector S: a collection of particles the average of each particles spin expectation value

along a given direction

spin vector and spin-orbit interaction

BμdtSd

s

S

N

Spin orbit interaction

N

I IAμ

S

BμdtJd

E.C. Aschenauer


Figure of merit of polarized proton collider

Luminosity: number of particles per unit area per unit

time. The higher the luminosity, the higher the collision

rates

beam polarization Statistical average of all the spin vectors.

zero polarization: spin vectors point to all directions. 100% polarization: beam is fully polarized if all spin

vectors point to the same directions.

)(

)(

4

1)(

2

2

0 t

tnNftL

rms

Transverse beam size

# of particles in one bunch

# of bunches

E.C. Aschenauer


Basics of circular accelerator

bending dipole Constant magnetic field Keeps particles circulating around the ring

quadrupole Magnetic field proportional to the distance from the

center of the magnet. Keeps particles focused

radio frequency cavities Electric field for acceleration and keeping beam

bunched longitudinally

E.C. Aschenauer


Closed orbit in a machine with dipole errors

Closed orbit ina perfect machine:center of quadrupoles

Closed orbit: particle comes back to the same position after one orbital revolution

Closed orbit in a circular accelerator

E.C. Aschenauer


))(2cos(2)( yyy sQJsy Beta function

Betatron tune: number of oscillations in one orbital revolution

Betatron oscillation in a circular accelerator

E.C. Aschenauer


Spin motion in circular accelerator: Thomas BMT Equation

In a perfect accelerator, spin vector precesses around the bending dipole field direction: vertical

Spin tune Qs: number of precessions in one orbital revolution. In general,

SBGBGm

eS

dt

Sd

])1([ //

€

Qs = Gγ

Spin vector in particle’s rest frame

B

beam

E.C. Aschenauer


polarized proton acceleration challenges:

preserve beam polarization Depolarization (polarization loss) mechanism

Come from the horizontal magnetic field which kicks the spin vector away from its vertical direction

Spin depolarizing resonance : coherent build-up of perturbations on the spin vector when the spin vector gets kicked at the same frequency as its precession frequency

xB

x

y

z

beam

Initial

xB

x

y

z

beam

1st full betatron Oscillation period

xB

x

y

z

beam

2nd full betatron Oscillation period E.C.

Aschenauer


spin depolarizing resonance

Imperfection resonance Source: dipole

errors, quadrupole mis-alignments

Resonance location:

G = k k is an integer

Intrinsic resonance Source: horizontal

focusing field from betatron oscillation

Resonance location:

G = kP±QyP is the periodicity of the

accelerator, Qy is the vertical betatron

tune

E.C. Aschenauer


Intr

insi

c sp

in r

eso

nan

ceQ

x=

28

.73

, Q

y=

29

.72

, em

it=

10

Spin depolarization resonance in RHIC

E.C. Aschenauer

For protons, imperfection spin resonances are spaced

by 523 MeV

the higher energy, the stronger the depolarizing resonance


First invented by Derbenev and Kondratenko from Novosibirsk in 1970s

A group of dipole magnets with alternating horizontal and vertical dipole fields

rotates spin vector by 180o

Innovative polarized proton acceleration techniques: Siberian

snake

E.C. Aschenauer


Particle trajectory in a snake:

E.C. Aschenauer


Use one or a group of snakes to make the spin tune to be 1/2

How to preserve polarization using Siberian snake(s)

xB

y

z

beam

xB

y

z

beam

Break the coherent build-up of the perturbations on the spin vector

E.C. Aschenauer


Accelerate polarized protons in RHIC

PHENIX (p)

AGSAlternating Gradient Synchrotron

LINACBOOSTER

Pol. H- Source

Solenoid Partial Siberian Snake

200 MeV Polarimeter

Helical Partial Siberian Snake

Spin Rotators(longitudinal polarization)

Siberian Snakes

Spin Rotators(longitudinal polarization)

Strong AGS Snake

RHIC pC PolarimetersAbsolute Polarimeter (H jet)

STAR (p)

AGS Polarimeters

Spin flipper

E.C. Aschenauer 32Varenna, July 2011

ANDY(p)


Polarized proton acceleration setup in RHIC

Energy: 23.8 GeV ~ 250 GeV (maximum store energy) A total of 146 imperfection resonances and

about 10 strong intrinsic resonances from injection to 100 GeV.Two full Siberian snakes

2

1 Qs

21s φφπ

1Q

E.C. Aschenauer


How do we know the protons are polarized


What is beam polarization?

Simple example: spin-1/2 particles (proton, electron)Can have only two spin states relative to certain axis Z: Sz=+1/2 and Sz =-1/2

2/12/1

2/12/1

ZZ

ZZ

SS

SS

NN

NNP

022

22

P

5.013

13

P

104

04

P

|P|<1

E.C. Aschenauer


How to measure proton beam polarization

There are several established physics processes sensitive to the spin direction of the transversely polarized protons

Scattering to the right

Scattering to the left

AN – the Analyzing Power (|AN|<1)(left-right asymmetry for 100% polarized protons)

NAP

Once AN is known:

=N

lef t−N

right

Nlef t

+ Nright

=ANP

E.C. Aschenauer


Polarization Measurements

RightLeft

RightLeft

NN NN

NN

AAP

1

AN depends on the process and kinematic range of the measurements

pC elastic scattering

NAP

N

11)( Precision of

the measurements

N=NLeft+NRight

For (P)=0.01 and AN~0.01 N~108 !Requirements:

Large AN or/and high rate (N)Good control of kinematic range

-t=2MCEkin

E.C. Aschenauer


RHIC and Polarimetry

E.C. Aschenauer

STAR (p)PHENIX (p)

AGS

LINAC BOOSTER


Spin RotatorsSolenoid Snake

Siberian Snakes

200 MeV Polarimeter

AGS pC CNI PolarimeterAC Dipole

RHIC pC Polarimeters

Absolute Polarimeter (H jet)

RHIC

Siberian Snakes

Cold Snake

Warm Snake

ANDY (p)


RHIC Polarimetry

Polarized hydrogen Jet Polarimeter (HJet)Source of absolute polarization (normalization to other polarimeters)Slow (low rates needs lo-o-ong time to get precise measurements)

Proton-Carbon Polarimeter (pC)Very fast main polarization monitoring toolMeasures polarization profile (polarization is higher in beam center)Needs to be normalized to HJet

Local Polarimeters (in PHENIX and STAR experiments)Defines spin direction in experimental areaNeeds to be normalized to HJet

All of these systems are necessary for the proton beam polarization measurements and

monitoringE.C. Aschenauer


Beam and target are both protons

Polarized H-Jet Polarimeter

beam

beam

target

target

PPtAN

target

target beam

beam PP

RHIC proton beam

Forward scatteredproton

H-jet target

recoil proton 02 inout ppt

Ptarget is provided by Breit Rabi Polarimeter

Left-right asymmetry in elastic scattering due to spin-orbit interaction: interaction between (electric or strong) field of one proton and magnetic moment associated with the spin of the other proton

E.C. Aschenauer

AN

=N

L−N

R

NL+ N

R

=

N

P


H-jet system

RHIC proton beam

Recoil proton

Height: 3.5 m

Weight: 3000 kg

Entire system moves along x-axis 10 ~ +10 mm to adjust collision point with RHIC beam.

IP12zy

x

target

E.C. Aschenauer


　 RF transitions (WFT or SFT)

|1> |2> |3> |4>

Separating Magnet (Sextuples)

H2 desociater

Holding magnet

2nd RF-transitions for calibration

P+ OR P

H = p+ + e

Atomic Beam Source

Scattering chamber

Breit-Rabi Polarimeter

Separating magnet

Ion gauge

|1> |3> |2> |4>

|1> |2>

|1> |2>

Ion gauge

Hyperfine structure

HJet target system

E.C. Aschenauer


HJet: Identification of Elastic Events

proton beam

Forward scatteredproton

proton target recoil proton

BLUE mode

YELLOW mode

Energy vs Channel #

ToF vs Energy

E.C. Aschenauer

Array of Si detectors measures TR & ToF of recoil proton. Channel # corresponds to recoil angle R.Correlations (TR & ToF ) and (TR & R ) the elastic process


HJet: Ptarget

1 day

Breit-Rabi Polarimeter:

Separation of particles with different spin states in the inhomogeneous magnetic field (ala Stern-Gerlach experiment)

Nuclear polarization

Very stable for entire run period !Polarization cycle

(+/ 0/ ) = (500/50/500) s

Source of normalization for polarization measurements at RHIC

Nuclear polarization of the atoms:

95.8% 0.1%

After background correction:

Ptarget = 92.4% 1.8%

E.C. Aschenauer


HJet:

Provides statistical precision (P)/P ~ 0.10 in a store (6-8 hours)

target

target beam

beam PP Example from Run-2006

εbeam

εtarget

t=-2MpEkin

Use the same statistics (with exactly the same experimental cuts) to measure beam and target

(selecting proper spin states either for beam or for target)

Many systematic effects cancel out in the ratio

Ekin (MeV)Ekin (MeV)

target

beam

HJet Provides very clean and stable polarization measurements but with limited stat. precision

Need faster polarimeter! E.C. Aschenauer


P-Carbon Polarimeter:

Ultra thin Carbon ribbon Target(5 mg/cm2)

1

34

5

6

2

Si strip detectors(TOF, EC)

18cm

Polarized proton

Recoil carbon

Carbon target

LL NN or

RR NN or

or

Left-right asymmetry in elastic scattering due to spin-orbit interaction: interaction between (electric or strong) field of Carbon and magnetic moment associated with the spin of the proton

Pbeam N

ANpC

N NL NR

NL NR

Target Scan mode (20-30 sec per measurement)

Stat. precision 2-3%

Polarization profile, both vertical and horizontal

Normalized to H-Jet measurements over many fills (with precision <3%)

E.C. Aschenauer


pC: AN

zero hadronic spin-flip

With hadronic spin-flip (E950)

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

pC Analyzing Power

Ebeam = 21.7GeVEbeam = 21.7GeV Ebeam = 100 GeVEbeam = 100 GeV

unpublishedRun04

hadflip

emflipnon

hadflipnon

emflipN CCA *

2

*

1

Elastic scattering: interference between electromagnetic and hadronic amplitudes in the Coulomb-Nuclear Interference

(CNI) region

E.C. Aschenauer


Polarization Profile

H-Jetp

~1 mm

6-7 mm

pC ColliderExperiments

P1,2(x,y) – polarization profile, I1,2(x,y) – intensity profile, for beam #1 and #2

x=x0),(),( 01011 yxIyxPP ),(),(),( 2111 yxIyxIyxPP ),(),( 111 yxIyxPP

If polarization changes across the beam, the average polarization seen by Polarimeters and Experiments (in

beam collision) is different

E.C. Aschenauer


Pol. Profile and Average Polarization

Carbon

Scan C target across the beamIn both X and Y directions

Target Position

Intensity

Polarizati

on

I

P

2

2

P

IR

YX

YX

YX

HJet

Exp RR

RR

RR

P

P

4

11

21

121

1

11

Run-2009:Ebeam=100 GeV: R~0.1 5% correction

Ebeam=250 GeV: R~0.35 15% correction

Ideal case: flat pol. profile (P= R=0)

E.C. Aschenauer


pC+HJet: Polarization vs Fill

Run-2009 results (Ebeam=100 GeV)

Normalized to HJetCorrected for polarization profile (by pC)

P/P < 5%

Dominant sources of syst. uncertainties:

~3% - HJet background

~3% - pC stability (rate dependencies, gain drift)

~2% - Pol. profile“Yellow” beam

“Blue” beam

E.C. Aschenauer


Need for Local Polarimeters

E.C. Aschenauer

ANDY(p)

STAR (p)PHENIX (p)

AGS

LINAC BOOSTER


Spin RotatorsSolenoid Snake

Siberian Snakes

200 MeV Polarimeter

AGS pC CNI PolarimeterAC Dipole

RHIC pC Polarimeters

Absolute Polarimeter (H jet)

RHIC

Siberian Snakes

Cold Snake

Warm Snake

Spin Rotators around experiments may change spin direction in experimental areas

Need to monitor spin direction in experimental areas


Local Polarimeter: PHENIX

Utilizes spin dependence of very forward neutron production discovered in RHIC Run-2002 (PLB650, 325)

neutronchargedparticles

Zero Degree Calorimeter

Quite unexpected asymmetryTheory can not yet explain itBut already can be used for polarimetry! PAN

E.C. Aschenauer


Monitor spin direction

Vertical f ~ ±p/2Radial f ~ 0Longitudinal no asymmetry

Measures transverse polarization PT , Separately PX and PY

Longitudinal component:P – from CNI polarimeters

22TL PPP

Vertical

Radial

Longitudinal

-/2 0 /2

Asymmetry vs

E.C. Aschenauer


STAR Local Polarimeter

3.3<|h|< 5.0 (small tiles only)

Utilizes spin dependence of hadron production at high xF:

Bunch-by-bunch (relative) polarization

E.C. Aschenauer

Monitors spin direction in STAR collision regionCapable to precisely monitor polarization vs time in a

fill, and bunch-by-bunch

Now we have the polarised proton beam and

know what the polarisation is,what is next

E.C. Aschenauer Varenna, July 2011 55

How do we measure things Detectors


BACKUP


Design parameters for RHIC pp

Parameter Unit p-p

relativistic , injection … 25.9

relativistic , store … 266.5

no of bunches, nb … 112

ions per bunch, Nb 1011 2.0

emittance eN x,y 95% mm-mrad 20

average luminosity 1030 cm-2s-1 150

polarization,store % 70

E.C. Aschenauer


Stern-Gerlach Experiment

Separation of spin states in the inhomogeneous magnetic field

E.C. Aschenauer


Summary Polarimetry is a crucial tool in RHIC Spin Program

Provides precise RHIC beam polarization measurements and monitoring

Provides crucial information for RHIC pol. beam setup, tune and development

RHIC Polarimetry consists of several independent subsystems, each of them playing their own crucial role (and based on different physics processes)

HJet: Absolute polarization measurements

pC: Polarization monitoring vs bunch and vs time in a fillPolarization profile

PHENIX and STAR Local Polarimeters: Monitor spin direction (through trans. spin component) at collision

E.C. Aschenauer

Documents

E.C. Aschenauer Varenna, July 20112 Large scientific instruments that produce and accelerate subatomic particles and ‘smashes them’ Fixed target