rhic: the first polarized proton collider

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JINR, Prague, July 27, 2005 RHIC: RHIC: the first the first polarized proton polarized proton collider collider Mei Bai Collider Accelerator Department Brookhaven National Laboratory

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RHIC: the first polarized proton collider. Mei Bai Collider Accelerator Department Brookhaven National Laboratory. Outline. General introduction of accelerator physics spin dynamics RHIC: the polarized proton collider Brief history of RHIC pp development achieved performance of RHIC pp - PowerPoint PPT Presentation

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Page 1: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

RHIC: RHIC: the first polarized the first polarized proton colliderproton collider

Mei Bai

Collider Accelerator DepartmentBrookhaven National Laboratory

Page 2: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Outline

General introduction of accelerator physics spin dynamics

RHIC: the polarized proton colliderBrief history of RHIC pp development achieved performance of RHIC pp highlights of RHIC pp developments

Summary

Page 3: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Synchrotron

The acceleration comes from the electric field with an oscillating frequency synchronized with the particle’s revolution frequency

Alternating gradient A proper combination of focusing and de-

focusing quadrupoles yields a net focusing/defocusing force in both horizontal and vertical planes

FODO cell: most popular building block for synchrotrons

EB

QF QD QF

L L

Rf cavity

12'1

2

101

10

11

101

10

11

2

101

'

x

x

f

L

f

L

fx

x

Page 4: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Particle motions in a synchrotron:

Longitudinal Synchrotron oscillation

Synchrotron tune

E

VhQsyn

2

E

t()

V

Page 5: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Particle motions in a synchrotron:

Transverse Betatron oscillation:

Betatron function: the envelope of the particle’s

trajectory along the machine

Beta tune: number of betatron oscillations in one

orbital revolution

0)(2

2

xsKds

xdx ))(2cos(2)( xxx sQJsx

Transverse Betatron oscillation:

Betatron function: the envelope of the particle’s

trajectory along the machine

Beta tune: number of betatron oscillations in one

orbital revolution

Page 6: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Spin dynamics: Spin motion in a circular accelerator

Thomas BMT equation

Spin tuney

x

z

B

S

beam directoin

SBGBGm

eS

dt

Sd

])1()1[( //

Gf

Qrev

s

1

GQs

In the frame which moves with the particle

Page 7: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Spin dynamics: Depolarization mechanism

Imperfection resonance Coherent perturbations on the spin precession

from horizontal dipole fields due to the non-zero closed orbit.

condition: Strength: size of the closed orbit distortion

Intrinsic resonance Coherent perturbations on the spin precession

from quadrupole fields Condition: Strength: size of the betatron oscillation amplitude

High order resonance

kG

yQkPG

Page 8: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Spin dynamics: Siberian snake

Full Siberian snake Rotate spin vector by 180o

Cancels the perturbation on

on the spin motion between

snakes

spin tune in the presence of

two snakes:

2

1 Qs 21s φφ

π

1Q

Page 9: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Spin dynamics: snake depolarization resonance

Condition

even order resonance When m is an even number Disappears in the two snake

case like RHIC if the closed orbit is perfect

odd order resonance When m is an odd number Driven by the intrinsic spin

resonances

Ram

p w

orki

ng p

t.

Sto

re w

orki

ng p

t.

3/4

5/6

7/85/8

kQmQ sy

Page 10: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

RHIC pp accelerator complex

BRAHMS & PP2PP (p)

STAR (p)

PHENIX (p)

AGS

LINACBOOSTER

Pol. H- Source

Spin Rotators(longitudinal polarization)

Solenoid Partial Siberian Snake

Siberian Snakes

200 MeV Polarimeter AGS Internal Polarimeter

Rf Dipole

RHIC pC PolarimetersAbsolute Polarimeter (H jet)

AGS pC PolarimetersStrong AGS Snake

Helical Partial Siberian Snake

PHOBOS

Spin Rotators(longitudinal polarization)

Spin flipper

Siberian Snakes

Installed and commissioned during FY04 run

installed and commissioned during FY05 run

Page 11: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

PHENIX (p)

AGS

LINACBOOSTER

Pol. H- Source

Solenoid Partial Siberian Snake

200 MeV Polarimeter

Helical Partial Siberian Snake

Spin Rotators(longitudinal polarization)

Siberian Snakes

Page 12: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Polarized proton collisions in RHIC

Page 13: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Design parameters for RHIC pp

Parameter Unit p-p

relativistic g, injection … 25.9

 relativistic g, store … 266.5

no of bunches, nb … 112

ions per bunch, Nb 1011 2.0

emittance eN x,y 95% mm-mrad 20

luminosity 1030 cm-2s-1 150

polarization,store % 70

Page 14: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Milestones of RHIC pp development

2000

New polarized proton source (OPPIS) commissionedOne snake was installed in the sector 9 in Blue ring By slowly turning on this snake after the pp was injected, a radial polarization was measured and demonstrated that the snake was working as expected

CNI polarimeter in Blue installed and commissioned

2002All snakes for both rings installed and commissionedCNI polarimeter in Yellow installed and commissioned

2003Spin rotators installed and commissioned provided longitudinal polarizations at STAR and PHENIX for physics data taking

2004RHIC absolute polarimeter using H Jet target installed and commissionedAGS 5% helical warm snake installed and commissioned

2005

New super-conducting solenoid was installed in the OPPIS sourcePolarized protons in RHIC were accelerated to 205 GeV with a measured polarization of 30% AGS 25% super-conducting helical snake installed and commission started

Page 15: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

RHIC pp achieved performance

Parameter Unit 2002 2003 2004 20052005

No. of bunches … 55 55 56 106106

 bunch intensity 1011 0.7 0.7 0.7 0.90.9

store energy GeV 100.2 100.2 100.2 100.2 100.2 

* m 1 1 1 1 1 

peak luminosity 1030cm-2s-1 2 6 6 1010

average luminosity 1030cm-2s-1 1.5 3 4 6 6 

Time in store % 30 41 38 5656

average polarization, store

% 15 35 46 4747  

Page 16: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

RHIC pp performance: delivered luminosity

Page 17: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Run5 RHIC p^p^ Delivered Integrated Luminosity

0.0

3.0

6.0

9.0

12.0

15.0

18.0

21.0

16-Ap

r

23-Ap

r

30-Ap

r

7-May

14-May

21-May

28-May

4-Jun

11-Jun

18-Jun

25-Jun

date

Inte

gra

ted

Lu

min

os

ity

[p

b^

-1]

BRAHMS

STAR

PHENIX

min

max

RHIC pp performance in 2005: delivered luminosity

Provided a total of 12.6pb-1 luminosity with longitudinal polarization at STAR and PHENIX

Page 18: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

49.5%

44.5%

RHIC pp performance in 2005: average polarization at store

Page 19: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

1.5

1.7

0.8

1.71.7

1.3

1.1

0.7

0.3

1.9

1.4

2.1

0.7

1.61.6

1.2

1.00.9

0.3

1.679

96

76

89

101 101 104107

80

71

0.0

0.5

1.0

1.5

2.0

2.5

4/16 to 4/22

4/23 to 4/29

4/30 to 5/06

5/07 to 5/13

5/14 to 5/20

5/21 to 5/27

5/28 to 6/03

6/04 to 6/10

6/11 to 6/17

6/18 to 6/24

period

inte

gra

ted

lu

mn

iosi

ty [

pb

^-1

] (l

on

git

ud

inal

p

ola

riza

tio

n)

0

20

40

60

80

100

120

Run 5 (p^p^) -- Integrated Luminosity by week

ho

urs

per

wee

k at

sto

re

Phenix STAR hours at store

Total hours in store: 904Total calendar hours: 1680Total hour for 205 GeV: 72

s =

41

0

GeV

develo

pm

en

t

RHIC pp performance in 2005: weekly luminosity

Page 20: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

RHIC pp performance in 2005: a typical week

Page 21: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

•106x106 bunches•Bunch intensity at injection: • Blue=0.99x1011, yellow=1.07x1011

The highest vacuum pressure rise was seen at• CNI polarimeter• IR10

Still below the vacuum limit at 5x10-6 Torr

RHIC pp performance in 2005: a typical store

Page 22: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Snake resonance observed in RHIC

¼ snake resonance

Coupled 3/14 snake resonance

Page 23: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Snake resonance observed in RHIC

7/10 snake resonance

Page 24: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

How to avoid snake resonance

Keep the spin tune as close to 0.5 as possible: snake current setting

Keep the betatron tunes away from snake resonance locations:Precise tune control Tune feedback

Page 25: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

-10

0

10

20

30

40

50

300 305 310 315 320 325 330 335

snake Inner Current [Amp]

po

lari

zati

on

Blue FY04 flatten orbit Yellow FY04 zero orbit Yellow FY05 Zero orbit

Blue FY05 flatten orbit Yellow FY05 flatten orbit

Snake current scan in RHICYellow:

• no difference between zero orbit and flatten orbit

Blue: • wider than FY04 and than yellow• weaker resonance?

Page 26: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Highlight of RHIC pp developments Quest for a new working point in RHIC

Operation year

*

[m]Qx, Qy

Tune width with

beam-beam

Peak luminosity

[cm-2s-1]

2002 30.235

0.2250.005 2x1030

2003 10.235

0.2250.005 6x1030

2004 10.735

0.7300.007 10x1030

2005 10.690

0.6850.007 10x1030

Page 27: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Highlight of RHIC pp developments working point exploration

good spot forpolarization aswell as for beamlifetime

a snake depolarizationresonanceMotivation for new working

point development:• good for polarization transmission efficiency• good beam lifetime under collisions• good polarization lifetime

Loss

rat

e

Cou

rtes

y of

R.

Tom

as

Working point during ramp

Page 28: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

p=217 GeVThis gives the same Brho as Cu and one can avoid an additional DX magnet training

Intr

insi

c sp

in r

eso

nance

Qx=

28.7

3,

Qy=

29.7

2,

em

it=

10

achieved

p=205 GeV is the compromise between machinepreference and PHOBOS intereston pp physics

at s=410 GeV

Highlight of RHIC pp developments s = 410 GeV development

Page 29: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

• 30% polarization was measured in both rings at 205 GeV per beam• Two polarization ramp measurements shows an increase of 1mm vertical rms in yellow decreased the polarization transmission efficiency by close to a factor of 2

Highlight of RHIC pp developments s = 410 GeV development

Page 30: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Highlight of RHIC pp developments s = 410 GeV development

• no polarization loss before 100 GeV• With yellow yrms increased by 1mm around the 1st strong at 135GeV• Blue vertical tune moved away from 0.7

Page 31: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Two partial snake scenario

Vertical component of stable spinSpin tune Courtesy of T. Roser

Extraction36+ intrinsic resonanceG

Vertical betatron tune

Page 32: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

AGS cold snake development: tune scan at 36+Qy

Prelim

inary

Prelim

inary

• 10% cold snake + 5% warm snake• experimental data agree well with spin simulation

Courtesy of H.H. Huang

Page 33: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Summary of AGS cold snake development

3 Tesla superconducting helical dipole snake installed in AGS Stable operation using four cryo-coolers Quickly reached performance of AGS without cold snake

Beam horizontal emittance is significantly smaller Maximum measured polarization:

~ 56% with 0.3x1011 protons per bunch Detailed studies show expected spin behavior Unexpected beam intensity dependence of polarization

Highest bunch intensity achieved 1.0x1011 with measured polarization of ~ 41%

Investigate various reasons• Tune spread• Insufficient correction of 9th harmonic of the vertical orbit• polarimeter saturation• Others …

Page 34: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Summary of AGS cold snake development

Several scenarios of optics correction of lattice distortions by the helical snake(s) were successfully tested. Possibly more corrections are needed to minimize the beam loss at injection which is the dominant factor in the available bunch intensity

Courtesy of H.H. Huang

Page 35: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Outlook of RHIC polarized protons

Luminosity: Goal: 150x1030 cm-2s-1 10x1030 cm-2s-1

Energy: 100 GeV 250 GeV

AGS cold snake: remove the dependence of beam polarization on bunch intensity

More NEG coated pipe: • 110 bunches with 2x1011 protons per bunch

Upgrade of RHIC pC polarimeter to avoid• the deterioration of the local vacuum pressure due to

excessive opening of vacuum pipe to replace the silicon detectors as well as C targets

Reduce the non-linearity errors from the triplets to reduce the beam-beam effect

Feedback system to combat the 10 Hz orbit jitter

Page 36: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Outlook of RHIC polarized protons

Luminosity: the 10 Hz orbit jitter has

been observed in RHIC. This effect leads to modulated beam-beam effect and blows up the beam emittance during a long store.

Page 37: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Outlook of RHIC polarized protons

Polarization Goal: 70% 50%

Snake current setting is critical to make sure the spin precession tune is very close to 0.5

• Using the pC polarimeter to measure the turn by turn spin precession at top energy to measure the spin tune

Precise tune control• Ongoing improvement of the RHIC online model• Better de-coupling technique• Tune feedback

Precise orbit control• Re-alignment of the machine• Improve the quality as well as the robustness of the BPM

system to achieve the rms value of the orbit distortion below 0.3mm

Page 38: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Closed orbit in RHIC

Flat orbit: Sum of kicks on the spin vector from quads as well as the dipole correctors = 0

Orbit through the center of bpms

• under 100 GeV, the orbit correction w.r.t. the zero orbit is sufficient for preserving the beam polarization• going beyond 100 GeV, the spin resonances are much stronger and simulation shows the spin prefers the flat orbit to the zero orbit• side effects of the flat orbit

• strong coupling of the betatron oscillation• enhance the imperfection resonance at a location of 81kG

Page 39: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Summary

Over the past 5 years, all the essential hardware and diagnostic apparatus for polarization are in place and successfully commissioned. RHIC has successfully accelerated polarized protons to 100 GeV with no polarization loss.

The RHIC pp run in 2005 is the first long pp run dedicated for physics data taking. RHIC performed well. The total delivered luminosity is well within the C-AD projection. The achieved polarization is above the projection thanks to the great performance of the polarized proton source and the injectors.

The 410 GeV development demonstrated the depolarization resonance is sensitive to the orbit distortion. Machine re-alignment will be arranged during the shutdown.

With the planned measures, we expect RHIC to achieve its design goals for polarized protons in the next couple of years

Page 40: RHIC:  the first polarized proton collider

JINR, Prague, July 27, 2005

Acknowledgement

L. Ahrens, I.G. Alekseev, J. Alessi, J. Beebe-Wang,M. Blaskiewicz, A. Bravar, J.M. Brennan, D. Bruno,G. Bunce, J. Butler, P. Cameron, R. Connolly, J. Delong,T. D’Ottavio, A. Drees, W. Fischer, G. Ganetis, C. Gardner, J. Glenn, T. Hayes, H-C. Hseuh. H. Huang, P. Ingrassia,U. Iriso-Ariz, O. Jinnouchi, J. Laster, R. Lee, A. Luccio,Y. Luo, W.W. MacKay, Y. Makdisi, G. Marr, A. Marusic,G. McIntyre, R. Michnoff, C. Montag, J. Morris, A. Nicoletti, P. Oddo, B. Oerter, J. Piacentino, F. Pilat, V. Ptitsyn,T. Roser, T. Satogata, K. Smith, D.N. Svirida, S. Tepikian,R. Tomas, D. Trbojevic, N. Tsoupas, J. Tuozzolo, K. Vetter, M. Milinski. A. Zaltsman, A. Zelinski, K. Zeno, S.Y. Zhang.