rhic: the first polarized proton collider
DESCRIPTION
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 PresentationTRANSCRIPT
JINR, Prague, July 27, 2005
RHIC: RHIC: the first polarized the first polarized proton colliderproton collider
Mei Bai
Collider Accelerator DepartmentBrookhaven National Laboratory
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
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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
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Particle motions in a synchrotron:
Longitudinal Synchrotron oscillation
Synchrotron tune
E
VhQsyn
2
E
t()
V
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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
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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
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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
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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
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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
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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
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PHENIX (p)
AGS
LINACBOOSTER
Pol. H- Source
Solenoid Partial Siberian Snake
200 MeV Polarimeter
Helical Partial Siberian Snake
Spin Rotators(longitudinal polarization)
Siberian Snakes
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Polarized proton collisions in RHIC
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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
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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
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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
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RHIC pp performance: delivered luminosity
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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
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49.5%
44.5%
RHIC pp performance in 2005: average polarization at store
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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
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RHIC pp performance in 2005: a typical week
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•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
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Snake resonance observed in RHIC
¼ snake resonance
Coupled 3/14 snake resonance
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Snake resonance observed in RHIC
7/10 snake resonance
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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
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-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?
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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
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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
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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
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• 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
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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
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Two partial snake scenario
Vertical component of stable spinSpin tune Courtesy of T. Roser
Extraction36+ intrinsic resonanceG
Vertical betatron tune
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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
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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 …
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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
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
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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.
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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
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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
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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
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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.