1. Collider Ring Optics & Related Issues
Vasiliy Morozov
for the JLab EIC Study Group

2. MEIC Layout Prebooster 0.2GeV/c  3-5 GeV/c protons Big booster
3-5GeV/c  up to 20 GeV/c
protons
3 Figure-8 rings
stacked vertically

3. Big Booster
Acceleration of protons from 3-5 GeV/c to up to 20 GeV/c for injection into ion collider ring
Big booster implementation options
Separate warm ring in collider rings’ tunnel (current baseline)
Using the electron ring
Separate cold ring in the prebooster’s tunnel
Big booster design considerations
Avoid transition energy crossing
Space charge  higher injection energy for larger ring
Matching RF systems  debunch low-frequency beam and then rebunch it at higher frequency?

4. Ion Collider Ring Layout
Geometrical matching of electron and ion rings
Spin rotators in the electron ring
Siberian snakes in the proton ring arcs
Siberian snake
Ion Ring
Electron Ring
Spin rotators

5. Modular Design Concept
Design separately and incorporate/match into the ring
Vertical chicanes for stacking the ion ring arcs on top of the electron ring
Injection section
Electron cooling section
Siberian snakes
Interaction region with horizontal crossing
Section for local chromaticity compensation

6. Adjusting quad strengths
Basic Ring Parameters
Proton beam momentum
GeV/c 60
Circumference m
Arc’s net bend
deg
240
Straights’ crossing angle
Arc length
300.5
Arc average radius
71.74
Straight section length
220.06
Lattice basic cell
FODO
Arc / straight FODO cell length
9 / 6.16
Nominal phase advance per cell x / y
90 / 90
Number of arc / straight FODO cells
54 / 68
Dispersion suppression
Adjusting quad strengths

7. Magnet Parameters Proton beam momentum GeV/c 60 Number of dipoles 108
Dipole length m 3
Bending radius
38.7
Bending angle
deg
4.4
Bending field T
5.2
Number of quads
288
Quad length
0.5
Quad strength in arc / straight FODO cells
T/m
130 / 195

8. Arc FODO Cell /2 betatron phase advance in both planes
Magnet parameters for 60 GeV/c protons:
Dipoles:
length = 3 m
bending radius = 38.7 m
bending angle = 4.4
bending field = 5.2 T
Quads:
length = 0.5 m
strength = 130 T/m

9. Dispersion Suppressor
Quads in 3 FODO cells varied to suppress dispersion while keeping -functions from growing
Maximum quad strength at 60 GeV/c = 148 T/m

10. Short Straight for Siberian Snake
Symmetric quad arrangement
Initial  values from the dispersion suppressor
Quads varied to obtain x,y = 0 in the middle at limited max
Maximum quad strength at 60 GeV/c = 130 T/m

11. Arc End with Dispersion Suppression
Indicated quads varied to suppress dispersion with limitations on max and Dmax
Maximum quad strength at 60 GeV/c = 212 T/m
Varied quads
Regular FODO
To straight section

12. Complete Arc
Length = m, net bend = 240, average radius = 72 m

13. Straight FODO Cell /2 betatron phase advance in both planes
Drift length chosen to close the ring’s geometry
Quad strength at 60 GeV/c = 195 T/m

14. Arc to Straight Matching Section
Four quads in two FODO cells adjusted to match ’s and ’s from arcs to straight’s standard FODO cell
Maximum quad strength at 60 GeV/c = 222 T/m

15. Complete Figure-8 Ring
Total length = 1041 m

16. Figure-8 Ring Layout
100 m

17. Summary of Optics Parameters
Proton beam momentum
GeV/c 60
Circumference m
Arc’s net bend
deg
240
Straights’ crossing angle
Arc length
300.5
Straight section length
220.06
Maximum horizontal / vertical  functions
20.8 / 20.8
Maximum horizontal dispersion Dx
2.01
Horizontal / vertical betatron tunes x,y
33.(03) / 33. (16)
Horizontal / vertical chromaticitiesx,y /
Momentum compaction factor 
4.7 10-3
Transition energy tr
14.58
Horizontal / vertical normalized emittance x,y
µm rad
0.35 / 0.07
At 20 GeV/c injection:
Maximum horizontal / vertical rms beam size x,y
15* horizontal / vertical beam stay clear mm
4 / 4
2 / 2
30 / 30