APS Division of Nuclear Physics: 2007 Long Range Plan Joint Town Meetings on Quantum Chromodynamics

e + p/A Facilities

Lia Merminga

Center for Advanced Studies of Accelerators

Jefferson Laboratory

January 12-14, 2007

Merminga, LRP2007, Jan 12-14 2007

  

Outline

   

EIC Design Specifications Proposed EIC Designs Luminosity Concepts Machine Designs

• • •

eRHIC ELIC LHeC R&D Required Performance Summary Conclusions

Merminga, LRP2007, Jan 12-14 2007

EIC Accelerator Design Specifications

       Various Drivers:  High L for spin physics (E cm  ~ 20+ GeV): Large Reach in x (down to 10 -4 Polarized H, D, ?) for large range in A 3 He  Parton dynamics at TeV energy scale Energy Asymmetry of ~10 Needs Flexible Center-of-mass energy for L/T Separation Average Luminosity ≥ 1x10 33 cm -2 sec -1 per Interaction Point Higher is essential at lower E cm range for “super- HERMES” Many Ion species of interest  Proton and neutron: Polarized H and D, 3 He desirable    Light-medium ions not necessarily polarized Up to Calcium for “EMC Effect” Up to A = 200+ for Saturation/CGC Longitudinal polarization of both beams in the interaction region (+Transverse polarization of ions +Spin-flip of both beams) all polarizations >70% desirable, need good ion polarimetry Positron Beams desirable, but lower luminosity seems o.k.

Merminga, LRP2007, Jan 12-14 2007

Proposed EIC Designs eRHIC L = 2.6x10

33

cm

-2

s

-1

E

cm

= 140 GeV ELIC L = 7.7x10

34

cm

-2

s

-1

E

cm

= 65 GeV LHeC L = 1.1x10

33

cm

-2

s

-1

E

cm

= 1.4 TeV L = 0.47x10

33

cm

-2

s

-1

E

cm

= 100 GeV

Luminosities are for e-p collisions Merminga, LRP2007, Jan 12-14 2007

Luminosity Concepts

Assuming equal electron/ion spot sizes at the IP:

L



fN i

2

r i



y

*

i

 1 

y x

 

i

r i fN i  * i,y  y i 

y

/



x

: Ion Energy : Classical Ion Radius : Ion Current : Ion Vertical β Function : Ion Beam-Beam Tune Shift : Beam Aspect Ratio Merminga, LRP2007, Jan 12-14 2007

Luminosity Concepts (cont’d)



i N i f [MHz] I i [A]



y i



* i,y (cm)



y /



x L [cm -2 sec -1 ] eRHIC ERL 250 2x10 11 14 0.42

0.015

26 1.0

2.6x10

33 * eRHIC R-R 250 1x10 11 14 0.21

0.0075

27 1.0

0.47x10

33 ELIC 150 0.4x10

10 1500 1 0.01

0.5

0.2

7.7x10

34 LHeC 7000 1.7x10

11 40 0.54

0.00032

50 0.94

1.1x10

33

Large  e allowed by ERL, allows for large N i . Short ion bunches allow large f, small

(*dedicated electron-ion operation and one collision point)



*.

Merminga, LRP2007, Jan 12-14 2007 Large 

i

Machine Designs

Merminga, LRP2007, Jan 12-14 2007

eRHIC

• Integrated electron-nucleon luminosity of ~ 50 fb -1 over about a decade for both highly polarized nucleon and nuclear (A = 2-208) RHIC beams.

   50-250 GeV polarized protons up to 100 GeV/n gold ions up to 167 GeV/n polarized 3He ions • Two accelerator design options developed in parallel (2004 Zeroth-Order Design Report):   ERL based design (“Linac-Ring”; presently most promising design): • Superconducting energy recovery linac (ERL) for the polarized electron beam.

• Peak luminosity of 2.6 goals.  10 33 cm -2 s -1 with potential for even higher luminosities.

• R&D for a high-current polarized electron source needed to achieve the design Ring-Ring option: • Electron storage ring for polarized electron or positron beam. • Technologically more mature with peak luminosity of 0.47  10 33 cm -2 s -1 .

• Decision on polarized leptons approach will be driven by a number of considerations, among them experimental requirements, cost and timeline.

Merminga, LRP2007, Jan 12-14 2007

ERL-based eRHIC Design

e cooling PHENIX

Main ERL (3.9 GeV per pass)

STAR

Four e-beam passes

e + storage ring 5 GeV 1/4 RHIC circumference

        Electron energy range from 3 to 20 GeV Peak luminosity of 2.6  10 33 cm -2 s -1 in electron-hadron collisions; high electron beam polarization (~80%); full polarization transparency at all energies for the electron beam; multiple electron-hadron interaction points (IPs) and detectors;  5 meter “element-free” straight section(s) for detector(s); ability to take full advantage of electron cooling of the hadron beams; easy variation of the electron bunch frequency to match it with the ion bunch frequency at different ion energies.

Merminga, LRP2007, Jan 12-14 2007

ERL-based eRHIC Parameters

Energy, GeV Number of bunches Bunch spacing, ns Bunch intensity, 10 11 (10 9 for Au) Beam current, mA 95% normalized emittance, πμm Rms emittance, nm  *, x/y, cm Beam-beam parameters, x/y Rms bunch length, cm Polarization, %

Peak Luminosity/n, 1.e33 cm -2 s -1 Aver.Luminosity/n, 1.e33 cm -2 s -1 Luminosity integral /week, pb -1

Electron-Proton Collisions High energy setup p e 250 20 Low energy setup p e 50 3 166 166 71 2 420 6 71 1.2

260 115 3.8

26 0.5

200 0.015

20 70

2.6

0.87

530

2.3

0.7

80 71 2.0

420 6 71 1.2

260 115 19 26 3.3

150 0.015

20 70

0.53

0.18

105

2.3

1.8

80 Electron-Au Collisions High energy setup Au e 100 20 Low energy setup Au e 50 3 166 166 71 1.1

180 2.4

71 1.2

260 115 3.7

26 0.5

200 0.015

20 0

2.9

1.0

580

1.0

0.7

0 71 1.1

180 2.4

71 1.2

260 115 7.5

26 3.3

60 0.015

20 0

1.5

0.5

290

1.0

1.8

0 Merminga, LRP2007, Jan 12-14 2007

Ring-Ring eRHIC Design

5 – 10 GeV e-ring 5 -10GeV Injector RHIC e-cooling

     Based on existing technology Collisions at 12 o’clock interaction region 10 GeV, 0.5 A e-ring with 1/3 of RHIC circumference (similar to PEP II HER) Inject at full energy 5 – 10 GeV Polarized electrons and positrons Merminga, LRP2007, Jan 12-14 2007

eRHIC R-R: Full Energy Injection Options

Polarized Electron Source 200 MeV 8 GeV 4 GeV Copper Linac, SLAC type cavities 200 MeV Positron Source 4 GeV

0 10 50 100 150 200

10 GeV 2 GeV 2 GeV 6 GeV

250 275 m

Polarized Electron Source 200 MeV SC Linac, Tesla type cavities 6.7 GeV 3.3 GeV 1.7 GeV 5 GeV 200 MeV 10 GeV Positron Source 3.3 GeV 8.3 GeV

0 10 50 100 150 200 250 275 m

Recirculating NC linac Recirculating SC linac • Injection of polarized electrons from source • Ring optimized for maximum current • Top-off Extraction 5 - 10 GeV

0 10 50

Injection 0.5 GeV Positron Source Polarized Electron Source, 20 MeV

100 150 m

Figure 8 booster synchrotron, FFAG or simple booster Merminga, LRP2007, Jan 12-14 2007

Ring-Ring eRHIC Parameters

Energy, GeV Number of bunches Bunch spacing Particles / bunch Beam current 95% normalized emittance Emittance e x Emittance e y  x*  y* Beam-beam parameter  x Beam-beam parameter  y Bunch length  z Polarization

Peak Luminosity Average Luminosity Luminosity Integral /week

GeV ns 10 11 mA p mm·mrad nm nm m m m %

10 33 , cm -2 s -1 10 33 , cm -2 s -1 pb -1

High energy setup p 250 165 e 10 55 71 1.00

208 71 2.34

483 15 9.5

9.5

1.08

0.27

53.0

9.5

0.19

0.27

0.015

0.0075

0.20

70

0.47 0.16

96

0.029

0.08

0.012

80 Low energy setup p 50 165 e 5 55 71 1.49

315 71 0.77

353 5 15.6

15.6

1.86

0.46

130 32.5

0.22

0.22

0.015

0.0075

0.20

70

0.082 0.027

17

0.035

0.07

0.016

80 Merminga, LRP2007, Jan 12-14 2007

eRHIC Ion Beam

• RHIC is the world’s only existing facility for high-energy heavy ion and polarized proton beams.

• 100 GeV proton beams with 65% polarization operational • First test at 250 GeV reached 45% polarization • First high energy stochastic cooling demonstrated in RHIC • Electron cooling under development for RHIC II (x10 luminosity). Also needed/beneficial for eRHIC • Presently RHIC operates with 111 bunches. eRHIC design is 166 bunches. Further increase to 333 bunches requires considerable R&D (injection kicker, electron clouds) but will double luminosity for both design options • Development under way for polarized 3 He beams from the new RHIC ion source EBIS Merminga, LRP2007, Jan 12-14 2007

ELIC

Green-field design of ion complex directly aimed at full exploitation of science program.

Electron Cooling IR

30-150 GeV light ions

IR Snake Snake

polarized source unpolarized source Transverse emittance

3-7 GeV electrons 3-7 GeV positrons

Positron source in 12 GeV CEBAF injector

- polarized source is off - dipoles are turned on Merminga, LRP2007, Jan 12-14 2007

Achieving Luminosity of ELIC

For 150 GeV protons on 7 GeV electrons, L~ 7.7 x 10 34 cm -2 sec -1 compatible with realistic Interaction Region design.

Beam Physics Concepts  Beam – beam interaction between electron and ion beams (  i/e ~ 0.01/.086 per IP; 0.025 largest achieved presently in Tevatron, and ~.1 for electrons )   High energy electron cooling Interaction Region • • • • High bunch collision frequency (f = 1.5 GHz) Short ion bunches (  z Very strong focus (  * ~ 5 mm) Crab crossing ~ 5 mm) Merminga, LRP2007, Jan 12-14 2007

Crab Crossing

Short bunches make Crab Crossing feasible.

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

SRF dipole F Final lens F Parasitic collisions are avoided without loss of luminosity.

Merminga, LRP2007, Jan 12-14 2007

Achieving Polarization in ELIC

Protons and 3 He

collision point collision point

• Polarization of ions

collision point collision point

Protons, 3 He: Two snakes to ensure 4 IP’s with longitudinal spin Deuterons: 2 IP’s with longitudinal spin - no snakes.

Solenoid to stabilize spin. • Polarization of electrons

i i

collision point collision point

- Spin injected vertical in arcs. - Self-polarization in arcs to maintain injected polarization.

collision point

So len oid

collision point

i i

- Spin rotators complementary to vertical bends of IPs for spin matching at IP.

4 IP’s with longitudinal spin • Polarization of positrons Sokolov-Ternov polarization for positrons Polarization time 2 hrs at 7 GeV 4 IP’s with longitudinal spin. Merminga, LRP2007, Jan 12-14 2007

ELIC Parameters

Parameter

Beam energy Bunch collision rate Number of particles/bunch Beam current Cooling beam energy Cooling beam current Energy spread, rms Bunch length, rms Beta-star Horizontal emittance, norm Vertical emittance, norm Beam-beam tune shift (vertical) per IP Laslett tune shift (p-beam) Luminosity per IP, 10 34 Number of interaction points Core & luminosity IBS lifetime

Unit

GeV GHz 10 10 A MeV A 10 -4 mm mm



m



m cm -2 s -1 h 150/7 1.5 .4/ 1.0

1/2.4 75 2 3/3 5/5 5/5 1/86 Ring-Ring 100/5 .4/1.1 1/2.7 50 2 .7/70 30/3 .12/1.7 .3/4.1 15 .6 .2/43 .04/3.4 .01

/ .086

.06/6 .01

/.073 .2/43 .01

/.007 .015 7.7 4 24 .03 5.6 24 .06 .8



24

Merminga, LRP2007, Jan 12-14 2007

ELIC Luminosity for Ions

Ion Max Energy (GeV/nucleon) *Luminosity at 7 GeV x E i,max *Luminosity at 3 GeV x E i,max /5 Proton Deuteron 3 H +1 3 He +2 4 He +2 12 C +6 40 Ca +20 *Luminosity per ion 150 75 50 100 75 75 75 7.8 × 10 34 7.8 × 10 34 7.8 × 10 34 3.9 × 10 34 3.9 × 10 34 1.3 × 10 34 3.9 × 10 33 6.7 × 10 33 6.7 × 10 33 6.7 × 10 33 3.3 × 10 33 3.3 × 10 33 1.1 × 10 33 3.3 × 10 32 Merminga, LRP2007, Jan 12-14 2007

Design Features of ELIC

 

Directly aimed at addressing the science program

:   “Figure-8” ion and lepton storage rings to ensure spin preservation and ease of spin manipulation. No spin sensitivity to energy for all species. Short ion bunches, low β*, and high rep rate (crab crossing) to reach unprecedented luminosity.

Four interaction regions for high productivity.

Physics experiments with polarized positron beam are possible. Possibilities for colliding beams.

e e -

 Present JLab DC polarized electron gun meets beam current requirements for filling the storage ring.

 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.

 Collider operation appears compatible with for fixed target program.

simultaneous

12 GeV CEBAF operation Merminga, LRP2007, Jan 12-14 2007

LHeC

A Lepton-Proton Collider in the LHC In parallel with proton-proton collisions

Design goals: Luminosity L = 1 ∙10 33 cm -2 s -1 Energy E cm = 1.4 TeV Design assumptions

: Based on LHC Proton beam parameters

E

e

= 70 GeV

Energy E p = 7 TeV Particles per Bunch N p Emittance e Np = 1.67 10 11 = 3.75 µm Bunch spacing Bunch Length t b  p = 25 ns = 7.55 cm

LHeC: a ring-ring collider. Lepton ring, a LEP-size storage ring, to be installed above the LHC magnets.

Merminga, LRP2007, Jan 12-14 2007

LHeC Luminosity

●

E = 70 GeV

● ●

RF power = 50 MW = 0.86 LEP = 28% CERN site RF power = synchrotron radiation 

I

e

= 74 mA

L~ 10 33 cm -2 sec -1 for 

xp

 

yp

 1

m

Merminga, LRP2007, Jan 12-14 2007

LHeC Interaction Region

Lepton-proton collisions at one IP Separator dipole Lepton low β triplet Merminga, LRP2007, Jan 12-14 2007

LHeC Interaction Region (cont’d)

Crab RF cavity is used for

p

-bunch rotation Merminga, LRP2007, Jan 12-14 2007

LHeC Parameters

Merminga, LRP2007, Jan 12-14 2007

R&D Required for eRHIC and ELIC

Merminga, LRP2007, Jan 12-14 2007

Common R&D Topics



Polarized

3

He production

• EBIS, the new ion source under construction at BNL, will provide the ability to produce polarized 3 He beams.

• The existing RHIC Siberian Snakes can be used to preserve beam polarization during acceleration.

• R&D required on polarization preservation as well as in the pre-accelerators. 

High energy hadron cooling (electron, stochastic)

Merminga, LRP2007, Jan 12-14 2007

High Energy Hadron Cooling Stochastic cooling

 Can be used to reduce beam tails and extend beam lifetime.  Being pursued at RHIC. Can increase RHIC average store luminosity.

Electron cooling

 Electron beam cooling required to suppress IBS, reduce beam emittances, provide short ion bunches.  Very effective for heavy ions (higher cooling rate), more difficult for protons.

 Very ambitious project.

Merminga, LRP2007, Jan 12-14 2007

Bunched Beam Stochastic Cooling at RHIC

Wall Current Monitor signal of cooled bunch. The higher bunch (Blue) has been cooled for about 90 minutes. The lower trace (Red) is the bunch before cooling started.

Cooling time ~ 7 hours Achieved cooling rate barely sufficient to counteract IBS

Merminga, LRP2007, Jan 12-14 2007

Relativistic Electron Cooling at FNAL

  Fermilab made the next step in electron cooling technology Main Parameters 4.34 MeV electron beam [x20 previous experience], 0.5 A DC Magnetic field in the cooling section - 100 G Feasibility of electron cooling with bunched beams remains to be demonstrated.

Merminga, LRP2007, Jan 12-14 2007

RHIC electron cooler: 2 pass ERL layout

6 54.5 MeV

from RHIC

54.5 MeV 8 30 MeV 4’ 7 4 1

to RHIC

5 Laser 4.7 MeV 2 1. SRF Gun, 2. Injection merger line 3. SRF Linac two 5-cell cavities and 3 rd harmonic cavity 4, 4’. 180° achromatic turns 3 5, 6. Transport lines to and from RHIC, 7. Ejection line and beam dump 8. Short-cut for independent run of the ERL.

Merminga, LRP2007, Jan 12-14 2007



R&D Required for eRHIC

R&D Required for Ion Beam – Applies to ERL and Ring-Ring eRHIC • Increase number of bunches in RHIC From 111 to 166 within reach – 333 require significant R&D  R&D Required for Electron Beam - For ERL-eRHIC only • High Current Polarized Electron Source Required average current 260 mA, 20 nC/bunch Present state of art in polarized photocathode source: 0.3 mA average current (CEBAF, ~1 mA is expected to be reached shortly), 10 nC/bunch (SLC), 50mA/cm 2 (CEBAF) CEBAF, ILC, EIC developments expected to accelerate progress. • Energy Recovery Linacs Required 10X260 mA at ~20nC/bunch Present state of art in SRF ERL: 2x10 mA at the JLab FEL at 135 pC/bunch New BNL and JLab SRF cavity designs provide Amp level stability.

 Linac ring beam-beam limits Merminga, LRP2007, Jan 12-14 2007

R&D Required for ELIC

 Beam dynamics with crab crossing Phase stability requirements Crab cavity technology Has never been implemented, KEK recently installed 500 MHz crab cavity  Ion space charge at stacking in pre-booster Present state of art: maximum space charge tuneshift in booster ~ 0.4

Required an order of magnitude higher. Conceptual solutions exist, require numerical studies, experimental verification. Merminga, LRP2007, Jan 12-14 2007

Performance Summary

E CM [GeV] eRHIC ERL 25-140 Species Polarization p,D, 3 He,e ,e + p,.., 238 U positrons YES Number of IR’s IR free space [m] L peak [cm -2 sec -1 ] Up to 4 ±5

2.6x10

33

**

eRHIC R-R 30-100 p,.., 238 U positrons YES 1 (2*) ±1

0.47x10

*Requires second ring **one IR

33 ELIC 20-65 p, .., 40 Ca positrons YES 4 ±2 (up to ±3)

7.7x10

34 LHeC 1400 p, positrons Not planned 1 1.2

1.1x10

33

Merminga, LRP2007, Jan 12-14 2007

Reports

Zero th –Order Design Report for the Electron-Light Ion Collider at CEBAF

B. Yunn, Y. Zhang A. Afanasev, A. Bogacz, A. Bruell, L. Cardman, Y. Chao, S. Chattopadhyay, E. Chudakov, P. Degtiarenko, J. Delayen, Ya. Derbenev, R. Ent, P. Evtushenko, A. Freyberger, J. Grames, A. Hutton, R. Kazimi, G. Krafft, R. Li, L. Merminga, M. Poelker, A. Thomas, C. Weiss, B. Wojtsekhowski,

Thomas Jefferson National Accelerator Facility

Newport News, Virginia, USA W. Fischer, C. Montag

Brookhaven National Laboratory

Upton, New York, USA V. Danilov

Oak Ridge National Laboratory

Oak Ridge, Tennessee, USA V. Dudnikov

Brookhaven Technology Group

New York, New York, USA P. Ostroumov

Argonne National Laboratory

Argonne, Illinois, USA V. Derenchuk

Indiana University Cyclotron Facility

Bloomington, Indiana, USA A. Belov

Institute of Nuclear Research

Moscow-Troitsk, Russia Editors: Ya. Derbenev, L. Merminga, Y. Zhang Merminga, LRP2007, Jan 12-14 2007

Summary

 In response to a developing compelling scientific case for a high luminosity, polarized electron-ion collider, to address fundamental questions in hadron Physics: Two distinct accelerator design concepts, eRHIC and ELIC, maximally and creatively utilizing existing facilities, are under development and promise to meet the required performance. An unpolarized EIC design based on LHC is under study.    eRHIC design options: • • ERL-based, presently most promising eRHIC option,

L p

eRHIC Ring-Ring, technologically more mature,

L p ~ 2.6



~ 0.47



10 33 10 33 cm cm -2 s -1 -2 .

s -1

.

ELIC uses CEBAF, a green-field design for ion complex,

L p ~ 7.7x10

34 cm -2 s -1 .

LHeC uses LHC, in parallel with proton-proton collisions,

L p ~ 1.1x10

33 cm -2 s -1 .

 Electron cooling is a critical R&D topic and prerequisite for high luminosity EIC designs. A rigorous electron cooling R&D program established at BNL. Luminosity above L p ~10 33 cm -2 s -1 requires substantial additional R&D.  Important to continue collaboration and cross-fertilization of ideas among accelerator groups and user communities in order to arrive at optimum EIC design for the science.

Merminga, LRP2007, Jan 12-14 2007