1. Accelerator and Interaction Region
Alex Bogacz
Center for Advanced Studies of Accelerators
EIC Detector Workshop at Jefferson Lab
June 4-5, 2010

2. 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.

3. Design Goals Energy Luminosity Ion Species Polarization
Electrons: to 11 GeV
Ions: 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

4. Collider Parameters

5. 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

6. Conceptual Layout Three compact rings: 3 to 11 GeV electron
Up to 12 GeV/c proton (warm)
Up to 60 GeV/c proton (cold)

7. 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

8. Figure-8 Collider Ring Collider Ring design is a compromise between:
total ring circumference: 1000 m
64 deg. crossing
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

9. Ion Ring – 900 FODO Cell
phase adv/cell: Dfx,y= 900
Arc quadrupoles:
$Lb=40 cm
$G= 14.4 kGauss/cm
Arc dipoles:
$Lb=180 cm
$B=60.0 kGauss
$ang=3.09 deg.
$rho = 33.4 meter
Arc quadrupoles
$Lb=40 cm
$G= 10.1kG/cm
beta chromaticity perturbation wave propagates with twice the betatron frequency – intrinsic cell-to-cell cancellation of chromatic terms (after two cells)

10. Ion Ring - Arc Optics 248 deg. Arc Arc – 120 meter Arc – 120 meter
Straight – 20 meter

11. Electron Ring – 1350 FODO Cell
Synchrotron radiation power per meter less than 20 kW/m
phase adv/cell: Dfx,y= 1350
Arc dipoles, 9 GeV:
$Lb=100 cm
$B=16.2 kGauss
$ang=3.09 deg.
$rho = 18.4 meter
emittance preserving optics
Quadrupoles
$Lq=50 cm
$G= ±4.5 kG/cm
<H> minimum
1350 FODO

12. Electron Ring - Arc Optics
248 deg. Arc
Arc – 120 meter
Arc – 120 meter
Straight – 20 meter

13. IR Detector - Layout

14. IR Optics (electrons) Natural Chromaticity: x = -47 y = -66 IP f19
800 5
BETA_X&Y[m]
DISP_X&Y[m]
BETA_X
BETA_Y
DISP_X
DISP_Y
l * = 3.5m IP
FF doublets f
Natural Chromaticity: x = y = -66

15. IR Optics (electrons at 5 GeV)IP 19
800 5
BETA_X&Y[m]
DISP_X&Y[m]
BETA_X
BETA_Y
DISP_X
DISP_Y 19
0.15
Size_X[cm]
Size_Y[cm]
Ax_bet
Ay_bet
Ax_disp
Ay_disp IP
Q4 Q3 Q2 Q1
Q1 G[kG/cm] = -2.8
Q2 G[kG/cm] = 3.1
Q3 G[kG/cm] = -2.0
Q4 G[kG/cm] = 2.0

16. IR Optics (ions) Natural Chromaticity: x = -88 y = -141 IP f50
3000 5
BETA_X&Y[m]
DISP_X&Y[m]
BETA_X
BETA_Y
DISP_X
DISP_Y
l * = 7m IP
FF triplet : Q3 Q2 Q1 f
Natural Chromaticity: x = y = -141

17. IR Optics (ions) at 60 GeV IP IP FF triplet : Q3 Q2 Q150
3000 5
BETA_X&Y[m]
DISP_X&Y[m]
BETA_X
BETA_Y
DISP_X
DISP_Y 50
0.25
Size_X[cm]
Size_Y[cm]
Ax_bet
Ay_bet
Ax_disp
Ay_disp IP
FF triplet : Q3 Q2 Q1
Q1 G[kG/cm] = -9.7
Q2 G[kG/cm] = 6.9
Q3 G[kG/cm] = -6.8

18. Chromaticity Compensation
uncompensated dispersion from the Arc
Dfx = 2 Dfy
Dfx = p
Pairs of sextupoles ‘minus identity’ apart – cancelation of spherical aberrations
Cancelation of higher order chromatic terms due to symmetry imposed correlations

19. IR Chromaticity Compensation
ions
Dfx = p
Dfx,y = p
Dfy = 3p IP
Arc end
Chromaticity Compensation with four families of sextupoles

20. Chromaticity Compensation
electrons
Dfx = p
Dfx,y = p IP
Arc end
Chromaticity Compensation with four families of sextupoles

21. Collider Ring – Tune Diagram
Working point above half integer a la KEKB:
Qx= Qy=31.531 37 36 32 31 5 4 3 2 1

22. Tune Chromaticity Correction
Large momentum acceptance and dynamic aperture

23. Figure-8 Collider Rings
total ring circumference: 1000 m

24. Figure-8 Collider Rings
total ring circumference: 1000 m

25. 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.