Accelerator and Interaction Region

Accelerator and Interaction Region

Alex Bogacz

Center for Advanced Studies of Accelerators

EIC Detector Workshop at Jefferson LabJune 4-5, 2010

EIC Efforts at JLab

For over a year…

We have explored a staged approach to EIC, focusing on science cases and accelerator designs for a low-to-medium energy EIC with similar design features (high luminosity (>1034), polarization (>80%), multiple detectors)

We have developed a conceptual design of a low-to-medium energy EIC based on CEBAF, and have therefore reduced the detector and accelerator technology R&D significantly, yielding a large cost saving compared to the full energy collider.

We are now engaged in accelerator design, optimizations and staged R&D for enabling technologies.

Design Goals

Energy

Electrons: 3 to 11 GeV

Ions: 20-60+ GeV protons, ~30 GeV/A ions

Luminosity

a few1034 cm-2 s-1 per interaction point over a wide range of s values

Multiple interaction points

Ion Species

Polarized H, D, 3He, possibly Li

Up to A = 208, all fully stripped

Polarization

Longitudinal at the IP for both beams, transverse for ions

Spin-flip for the electron beam:

All polarizations >80% desirable

Positron Beam desirable

Collider Parameters

Proton Electron

Beam energy GeV 60 5

Collision frequency GHz 1.5 1.5

Particles / bunch 1010

0.416 1.25

Beam current A 1 3

Polarization % >70 ~80

Energy spread 10-4

~3 7.1

RMS bunch length mm 10 7.5

Horizontal and vertical β* cm 10/2 10/2

Hori. & Vert. emittance, normalized μm 0.35/0.07 54/11

Vert. beam-beam tune shift per IP 0.007 0.03

Laslett tune shift 0.07 small

Luminosity per IP, 1033

cm-2

s-1

30 30

Design Features

High luminosity at medium energy range

Enabled by short ion bunches, low β*, high rep. rate

Require crab crossing colliding beams

Electron cooling is an essential part of MEIC

Multiple IPs (detectors)

“Figure-8” electron and ion collider rings

Ensure spin preservation & ease spin manipulations

No spin sensitivity to energy for all species.

12 GeV CEBAF injector meets storage-ring polarized beam

requirements, can serve as a full energy injector

Conceptual Layout

Three compact rings:• 3 to 11 GeV electron• Up to 12 GeV/c proton (warm)• Up to 60 GeV/c proton (cold)

Collider Rings with ‘Relaxed’ IR Optics

Larger Figure-8 Rings (~1000 m circumference)

5 Tesla bends for ions at 60 GeV

Additional straights to accommodate spin rotators and RF

Horizontal IR crossing, dispersion free straights

‘Relaxed’ IR Design:

Chromaticity Compensating Optics

Uncompensated dispersion in the straights

Anti-symmetric dispersion pattern across the IR

Dedicated Symmetric Inserts around the IR

Electron Collider Ring based on emittance preserving Optics

max 32.5 10 m *

*

10

2

x

y

cm

cm

Figure-8 Collider Ring

Collider Ring design is a compromise between:

Minimizing synchrotron radiation effects prefers a large size ring

Space charge effect of ion beam prefers a compact ring

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Figure-8 Collider Ring - Footprint

total ring circumference: 1000 m

64 deg. crossing

Arc quadrupoles:

$Lb=40 cm

$G= 14.4 kGauss/cm

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PH

AS

E_

X&

Y

Q_X Q_Y

Ion Ring – 900 FODO Cell

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&Y

[m]

DIS

P_

X&

Y[m

]BETA_X BETA_Y DISP_X DISP_Y

phase adv/cell: x,y= 900

Arc dipoles:

$Lb=180 cm

$B=60.0 kGauss

$ang=3.09 deg.

$rho = 33.4 meter

beta chromaticity perturbation wave propagates with twice the betatron frequency – intrinsic cell-to-cell cancellation of chromatic terms (after two cells)

Arc quadrupoles

$Lb=40 cm

$G= 10.1kG/cm

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&Y

[m]

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BETA_X BETA_Y DISP_X DISP_Y

Ion Ring - Arc Optics

Straight – 20 meter Arc – 120 meter

248 deg. Arc

Arc – 120 meter

1350 FODO

Arc dipoles, 9 GeV:

$Lb=100 cm

$B=16.2 kGauss

$ang=3.09 deg.

$rho = 18.4 meter

<H> minimum

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[m]

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Electron Ring – 1350 FODO Cell

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0P

HA

SE

_X

&Y

Q_X Q_Y

Synchrotron radiation power per meter less than 20 kW/m

emittance preserving optics

Quadrupoles

$Lq=50 cm

$G= ±4.5 kG/cm

phase adv/cell: x,y= 1350

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&Y

[m]

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Electron Ring - Arc Optics

Straight – 20 meter Arc – 120 meter

248 deg. Arc

Arc – 120 meter

IR Detector Layout

solenoid

electron FFQs100 mrad

0 mrad

ion dipole w/ detectors

(approximately to scale)

electrons

I P

detectors

2+3 m 2 m 2 m

IR Optics (electrons)

2 1

* *IR

f f

f

Natural Chromaticity:

x = -47 y = -66

190

800

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


*

*

10

2

x

y

cm

cm

l * = 3.5m

IP

FF doublets

f

*2 2

* 223.5

6 102 10

ff m

2*

*( )

max0FFg

IR Optics (electrons at 5 GeV)6

6

22 10

4.4 10

xN

yN

m

m

*

*

10

2

x

y

cm

cm

Q4 Q3 Q2 Q1 Q1 G[kG/cm] = -2.8Q2 G[kG/cm] = 3.1Q3 G[kG/cm] = -2.0Q4 G[kG/cm] = 2.0

* 6

* 6

15 10

3 10

x

y

m

m

190

0.15

0

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e_X

[cm

]

Siz

e_Y

[cm

]

Ax_bet Ay_bet Ax_disp Ay_disp

IP

*( ) N

IP

190

800

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


IR Optics (ions)

2 1

* *IR

f f

f

Natural Chromaticity: x = -88 y = -141

500

3000

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


l * = 7m

IP

FF triplet : Q3 Q2 Q1

f

*3

*2 2

2

7

2 12.

05 10ff m

2

**

( )

*

*

10

2

x

y

cm

cm

max

0FFg

500

0.25

0

0.25

0

Siz

e_X

[cm

]

Siz

e_Y

[cm

]

Ax_bet Ay_bet Ax_disp Ay_disp

IR Optics (ions) at 60 GeV

IP

6

6

0.15 10

0.03 10

xN

yN

m

m

*

*

10

2

x

y

cm

cm

Q1 G[kG/cm] = -9.7Q2 G[kG/cm] = 6.9Q3 G[kG/cm] = -6.8

* 6

* 6

15 10

3 10

x

y

m

m

*( ) N

FF triplet : Q3 Q2 Q1

IP

500

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0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


Chromaticity Compensationuncompensated dispersion from the Arc

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[m]

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x

y

xPairs of sextupoles ‘minus identity’ apart – cancelation of spherical aberrations

Cancelation of higher order chromatic terms due to symmetry imposed correlations

IR Chromaticity Compensation

Chromaticity Compensation with four families of sextupoles

393.6255

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5-5

BE

TA

_X

&Y

[m]

DIS

P_

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]


x

x

x,y y

IP

Arc end

ions

Chromaticity Compensation

Chromaticity Compensation with four families of sextupoles

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[m]

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x

x,y

IP

Arc end x

electrons

Collider Ring – Tune DiagramWorking point above half integer a la KEKB: Qx=36.506 Qy=31.531

3736

3231

5 4 3 2 1

Tune Chromaticity Correction

Large momentum acceptance and dynamic aperture


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Figure-8 Collider Rings

Figure-8 Collider Rings


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Summary

MEIC EIC at JLab promises to accelerate and store a wide variety of polarized light ions and un-polarized heavy ions in collision with polarized electron or positron beam enabling a unique physics program.

The project covers a wide CM energy range (10 to 100 GeV) in a coherent way. In the immediate future, a low-to-medium energy collider (CM energy 10 to 50 GeV) is our immediate goal & R&D focus.

The collider luminosity for e-p collisions should reach ~1034 cm-2s-1 at (60x3~52 GeV2)

The project is now based on mostly proven accelerator technologies. Making a high intensity ion beam with high repetition rate, small emittance and short bunch length is a key to reaching the luminosity goals (advanced cooling techniques are required).

We have identified critical accelerator R&D topics for the project, We are currently pursuing staged accelerator design studies to validate and further optimize our design.

Accelerator and Interaction Region

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