An Electron-Ion Collider for JLab · 2007. 4. 24. · An Electron-Ion Collider for JLab Ya. Derbenev, B. Yunn, A. Bogacz, G. A. Krafft, L. Merminga, Y. Zhang. Center for Advanced

Thomas Jefferson National Accelerator Facility Page 1

L. Merminga Users Group Meeting, June 12-14 2006

An ElectronAn Electron--Ion Collider Ion Collider for JLabfor JLab

Ya. Derbenev, B. Yunn, A. Bogacz, G. A. Krafft, L. Merminga, Y. Zhang

Center for Advanced Studies of Accelerators

“The Expanding Physics of Jefferson Lab”Users Group Workshop and Annual Meeting

Jefferson Lab June 12-14, 2006



OutlineOutlineNuclear Physics Motivation / Requirements

ELIC: An Electron-Light Ion Collider at CEBAF

Achieving the Luminosity of ELIC

Achieving Polarization in ELIC

ELIC Parameters

Advantages/Features of the ELIC Design

R&D Required

Summary



Nuclear Physics MotivationNuclear Physics Motivation

A high luminosity polarized electron – light ion colliderhas been proposed as a powerful new microscope to probe the partonic structure of matter.

Over the past two decades we have learned a great amount about the hadronic structure.

Some crucial questions remain open …



CEBAF II/ELIC Upgrade CEBAF II/ELIC Upgrade -- ScienceScienceScience addressed by the second Upgrade:

• How do quarks and gluons provide the binding and spin of the nucleons?

• How do quarks and gluons evolve into hadrons?

• How does nuclear binding originate from quarks and gluons?

From A. W. Thomas at NSAC LRP implementation review (2005)

12 GeVELIC

g (x 0.01)

Glue ÷100



The features of the facility necessary to address these questions:

• Center-of-mass energy between 20 GeV and 65 GeV

with energy asymmetry of ~10, which yields

Ee ~ 3 GeV on Ei ~ 30 GeV up to Ee ~ 7 GeV on Ei ~ 150 GeV

• CW Luminosity from 1033 to 1035 cm-2 sec-1

• Longitudinal polarization of both beams in the interaction region ≥

50% –80% required for the study of generalized parton distributions and transversity

• Transverse polarization of ions extremely desirable

• Spin-flip of both beams extremely desirable

Nuclear Physics RequirementsNuclear Physics Requirements

Presenter�

Presentation Notes�

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Ion Linac and pre-booster

IR IR

Beam Dump

Snake

CEBAF with Energy Recovery

3-7 GeV electrons 30- 150 GeV light ions

Solenoid


IR IR

Beam Dump

Snake


3-7 GeV electrons 30- 150 GeV light ions

Solenoid


IR IR

Beam Dump

Snake


3 -7 GeV electrons 30 -150 GeV light ions

Solenoid

Electron Injector

Electron Cooling

ERLERL--based ELIC Designbased ELIC Design



Polarized electron current of 10’s of mA is required for ERL-based ELIC with circulator ring. Present state of art ~0.3 mA.

A fast kicker with sub-nanosecond rise/fall time is required to fill the circulator ring. Present state of art is ~10 nsecs.

Substantial upgrades of CEBAF and the CHL (beyond the 12 GeV Upgrade) are required. Integration with the 12 GeV CEBAF accelerator is challenging.

Exclusion of physics experiments with positron beam.

Electron cooling of the high energy ion beam is required.

Challenges of ERLChallenges of ERL--based ELICbased ELIC

Presenter�


�



Electron Cooling

Snake

Snake

3-7 GeV electrons

30-150 GeV light ions

IR

IR

A New Concept for ELICA New Concept for ELIC



Polarized Electron Injection & StackingPolarized Electron Injection & Stacking

J Storage ring

t

J

t

3000 pulses5μs

Injector

4ms*1 mA

*4 ms is the radiation damping time at 7 GeV

Presenter�


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Low emittance e- storage ring at 7 GeV

footprint

-16000

-8000

0

8000

16000

0 10000 20000 30000

z [cm]

x [cm]

300175 m

100 m

360

Mon Jun 12 14:58:12 2006 OptiM - MAIN: - D:\ELIC\Elecrton Ring\FODO_135_152_cell.opt

100

0.05

0

BET

A_X

&Y[

m]

DIS

PX

&Y

[m]

BETA_X BETA_Y DISP_X DISP_Y 360

Mon Jun 12 14:59:53 2006 OptiM - MAIN: - D:\ELIC\Elecrton Ring\FODO_135_152_cell.opt

100

0.05

0

BE

TA_X

&Y

[m]

DI S

PX

&Y

[m]

BETA_X BETA_Y DISP_X DISP_Y

DipolesL= 50 cmB = 6.4 kG

QuadsL= 30 cmG = 16 kG/cm

Emittance = 8.5 mm-mrad(norm. rms)

1350 FODO lattice - Thanks, Andrew Hutton!

19x8 cells80 cells 80 cells

Presenter�


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“Optimum” emittance e- ring at 7 GeV

footprint

-16000

-8000

0

8000

16000

0 10000 20000 30000

z [cm]

x [cm]

300175 m

100 m

DipolesL= 100 cmB = 6.8 kG

QuadsL= 60 cmG = 4 kG/cm

Emittance = 85 mm-mrad(norm. rms)

400

Mon Jun 12 14:15:19 2006 OptiM - MAIN: - D:\ELIC\Elecrton Ring\FODO_135_72_Figure8.opt

15

0

0.2

0

BE

TA

_X

&Y

[m]

DIS

P_X

&Y

[m]


Mon Jun 12 14:18:46 2006 OptiM - MAIN: - D:\ELIC\Elecrton Ring\FODO_135_72_Figure8.opt

15

0

0.2

0

BE

TA

_X

&Y

[m]

DIS

P_X

&Y

[m]


9x8 cells40 cells 40 cells

1350 FODO lattice



Ion ComplexIon Complex

Source

120 keV 3 MeV

RFQ DTL

50 MeV

CCL

200 MeVPre-Booster

3 GeV/cC~75-100 m

Large Booster(CR)

20 GeV

Collider Ring

Source Linac 200 MeV

Pre-Booster3 GeV/c

C~75-100 mIon Large Booster 20 GeV

(Electron Storage Ring)

Ion Collider Ring

spin

“Figure-8” boosters and storage rings• Zero spin tune avoids intrinsic spin resonances.• No spin rotators required around the IR.• Ensure longitudinal polarization for deuterons at 2 IP’s simultaneously, at all energies.



footprint

-16000

-8000

0

8000

16000

0 10000 20000 30000

z [cm]

x [cm]

Figure-8 Ion Ring at 150 GeV −

Lattice

17 cells 17 cells15 cells 15 cells

1080

Wed Dec 07 12:46:56 2005 OptiM - MAIN: - D:\ELIC\Figure-8\FODO\low_emitt\spr_in.opt

30

0

2-2

BE

TA

_X

&Y

[m]

DIS

P_

X&

Y[m

]


Wed Dec 07 12:51:16 2005 OptiM - MAIN: - D:\ELIC\Figure-8\FODO\low_emitt\spr_in.opt

30

0

2-2

BE

TA

_X

&Y

[m]

DIS

P_

X&

Y[m

]


300175 m

100 m



Positrons!Positrons!Generation of positrons: (based on CESR experience)

Electron beam at 200 MeV yields unpolarized positron accumulation of ~100mA/min½ hr to accumulate 3 A of positron current

Possible applications:e+i colliding beams (longitudinally polarized)e+e- colliding beams (longitudinally polarized up to 7x7 GeV)…..



Electron Cooling

Snake

Snake

3-7 GeV electrons

30-150 GeV light ions

IR

IR

3-7 GeV positrons

ELIC for PositronsELIC for Positrons



Achieving the Luminosity of ELICAchieving the Luminosity of ELIC

For 150 GeV protons on 7 GeV electrons, L~ 7.7 x 1034 cm-2 sec-1

compatible with realistic Interaction Region design.Beam Physics Issues

Beam – beam interaction between electron and ion beams

(ξi ~ 0.01 per IP; 0.025 is presently utilized in Tevatron)

High energy electron cooling

Interaction Region

• High bunch collision frequency (f = 1.5 GHz)

• Short ion bunches (σz ~ 5 mm)

• Very strong focus (β* ~ 5 mm)

• Crab crossing

*24i e

bN NL fπσ

=



Beam cooling required to suppress IBS and reduce emittancesBunch length shortening particularly important

EC for RHIC • 55 MeV ERL at 100 mA electron beam• Use of an SRF gun• R&D in progress

EC for ELIC • 75 MeV at 2A electron beam• Use circulator ring with 100 revolutions• Staged cooling

Electron CoolingElectron Cooling



ELIC Interaction Region ConceptELIC Interaction Region Concept

Focal Points

2 m

spin detectorCrab cavity

Crab cavity

focusing triplet

focusing triplet

80 MV

focusing doublet

focusing doublet

Crab cavity

Crab cavity

spin tune solenoid

spin tune solenoid

cross bend

cross bend

α

0.1 rad

4 m

i

e

i

4 m

0.1 rad



Short bunches make Crab Crossing feasible.

SRF deflectors at 1.5 GHz can be used to create a proper bunch tilt.

SRF dipole

Final lens FF

Crab CrossingCrab Crossing

Parasitic collisions are avoided without loss of luminosity.



max quad gradient ∼ 250 Tesla/m

ELIC Interaction Region DesignELIC Interaction Region Design

38.40

Fri Sep 24 09:14:55 2004 OptiM - MAIN: - D:\Collider Ring\ELIC\IR_i\iIR.opt

6000

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


IR for ions at E = 150 GeV

BETA

X a

nd Y

[m]

600

0



ELIC Interaction Region DesignELIC Interaction Region Design

39.40

Fri Sep 24 09:10:30 2004 OptiM - MAIN: - D:\Collider Ring\ELIC\IR_i\eIR.opt

3000

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


BETA

X a

nd Y

[m]

300

0 IR for electrons at E = 7 GeV



Achieving Polarization in ELICAchieving Polarization in ELIC

Polarization of Ions (protons, deuterons, 3He)

Polarization of Electrons

Polarization of Positrons



Polarization of IonsPolarization of Ions

Protons and 3He:Two IP’s (along straight section) with simultaneous longitudinal polarization with no snakes. Two snakes are required to ensure longitudinal polarization at 4 IP’s simultaneously.Deuterons: Two IP’s with simultaneous longitudinal polarization with no snakes (can be switched between two cross-straights).Solenoid (or snake for protons) to stabilize spin near longitudinal direction for all species.

collision point

collision point

collision point

collision point

Snake

P, He3

Protons and 3He

collision point

collision point

collision point

collision point

Solenoid

d

Deuterons



Polarization of ElectronsPolarization of Electrons

Spin injected vertical in arcs (using Wien filter). Self-polarization in arcs to maintain injected polarization. Spin rotators matched with the cross bends of IPs.

spin rotator

spin rotator

spin rotator

spin rotator

collision point

spin rotator with 90º

solenoid snake

collision point

collision point

collision point


solenoid snake



Electron Spin Matching at the IRElectron Spin Matching at the IR

Rotation of spin from vertical in arcs to longitudinal at IP: - Beam crossing bend causing energy-dependent spin rotation, together with- Energy-independent orbit spin rotators [two SC solenoids with bend in the middle] in the arc and after the arc.

snake solenoid

spin rotator spin rotator

collision point collision point

Spin tune solenoid

spin tune solenoid

spin tune solenoid

spin tune solenoid

ii

ee

spin

90º 90º



Polarization for PositronsPolarization for Positrons

Sokolov-Ternov polarization for positronsVertical spin in arcs 4 IP’s with longitudinal spinPolarization time is 2 hrs at 7 GeV – varies as E-5 (can be accelerated by introduction of wigglers or polarizing at maximum energy).Quantum depolarization in spin rotators ->Equilibrium polarization ≤

90%

spin rotator

spin rotator

spin rotator

spin rotator

collision point


solenoid snake

collision point

collision point

collision point


solenoid snake



Parameter Unit Energy GeV 3 5 7 Beam cross bend at IP mrad 70 Radiation damping time ms 50 12 4 Accumulation time s 15 3.6 1 Self-polarization time* h 20 10 2 Equilibrium polarization, max** % 92 91.5 90 Beam run time h Lifetime

ee-- / e/ e++ Polarization ParametersPolarization Parameters

*One e-folding. Time can be shortened using high field wigglers.**Ideal max equilibrium polarization is 92.4%. Degradation is due

to radiation in spin rotators.



ELIC ParametersELIC Parameters Parameter Unit ERL Ring-Ring Beam energy GeV 150/7 150/7 100/5 30/3 Bunch collision rate GHz 1.5 Number of particles/bunch 1010 .4/1.0 .4/1.0 .4/1.1 .12/1.7 Beam current A 1/2.4 1/2.4 1/2.7 .3/4.1 Cooling beam energy MeV 75 75 50 15 Cooling beam current A 2 2 2 .6 Energy spread, rms 10-4 3/3 Bunch length, rms mm 5/5 Beta-star mm 5/5 Horizontal emittance, norm μm 1/86 1/86 .7/70 .2/43 Vertical emittance, norm μm .04/3.4 .04/3.4 .06/6 .2/43 Beam-beam tune shift (vertical) per IP

.01/.086 .01/.086 .01/.073 .01/.007

Laslett tune shift (p-beam) .015 .015 .03 .06 Luminosity per IP, 1034 cm-2 s-1 7.7 7.7 5.6 .8 Number of interaction points 4 Core & luminosity IBS lifetime h 24 24 24 > 24



Advantages/Features of ELICAdvantages/Features of ELICJLab DC polarized electron gun already meets beam current requirements for filling the storage ring.

A conventional kicker already in use in many storage rings would be sufficient.

The 12 GeV CEBAF accelerator can serve as an injector to the ring. RF power upgrade might be required later depending on the performance of ring.

Physics experiments with polarized positron beam are possible.

Possibilities for e+e-, e-e-, e+e+ colliding beams.

No spin sensitivity to energy and optics.

No orbit change with energy despite spin rotation.

Collider operation appears compatible with simultaneous 12 GeV CEBAF operation for fixed target program.



R&D Required for RingR&D Required for Ring--Ring ELICRing ELIC

High energy electron cooling of protons/ions.Beam dynamics issues with crab crossing.Ion space charge at stacking in pre-booster.Beam-beam interactions.



Workshop on Future Prospects in QCD at High EnergyJoint EIC2006 & Hot QCD Meeting Hosted by Brookhaven National Laboratory

Date: July 17-22, 2006Location: Brookhaven National Laboratory



SummarySummaryA compelling scientific case is developing for a high luminosity, polarized electron-light ion collider, to address fundamental questions in hadron Physics.

JLab design studies have led to an approach that promises luminosities up to nearly 1035 cm-2 sec-1, for electron-light ion collisions at a center-of-mass energy between 20 and 65 GeV.

A fundamentally new approach has led to a design that can be realized on the JLab site using CEBAF as a full energy injector into an electron storage ring and can be integrated with the 12 GeV fixed target program for physics.

This ring-ring design requires significantly less technological development compared to the ERL-based design, for the same luminosity level.

Planned R&D will address open readiness issues.



Lifetime due to Background ProcessesLifetime due to Background Processes

Proton beam lifetime from small-angle elastic ep-scattering

Courtesy: A. Afanasev, et al.Contributions from inelastic processes have smaller effect by factor of ~10

5 days

Documents

An Electron-Ion Collider for JLab · 2007. 4. 24. · An Electron-Ion Collider for JLab Ya. Derbenev, B. Yunn, A. Bogacz, G. A. Krafft, L. Merminga, Y. Zhang. Center for Advanced