1. CASA Collider Design Review Retreat Other Electron-Ion Colliders: eRHIC, ENC & LHeC
Yuhong Zhang
February 24, 2010

2. eRHIC: Ring-Ring Based on existing technology
5 – 10 GeV e-ring
e-cooling
(RHIC II)
5 -10GeV full energy injector
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

3. eRHIC Ring-ring: Full Energy Injection Options
Recirculating SC linac
Recirculating NC linac
Injection of polarized electrons from source
Ring optimized for maximum current
Top-off
Figure 8 booster synchrotron,
FFAG or simple booster

4. eRHIC Ring-ring: Parameters
High energy setup
Low energy setup p e
Energy, GeV
GeV
250 10 50 5
Number of bunches
165 55
Bunch spacing ns 71
Particles / bunch
1011
1.00
2.34
1.49
0.77
Beam current mA
208
483
315
353
95% normalized emittance
p mm·mrad 15
Emittance ex nm
9.5
53.0
15.6
130
Emittance ey
32.5
bx* m
1.08
0.19
1.86
0.22
by*
0.27
0.46
Beam-beam parameter xx
0.015
0.029
0.035
Beam-beam parameter xy
0.0075
0.08
0.07
Bunch length sz
0.20
0.012
0.016
Polarization % 70 80
Peak Luminosity
1033 , cm-2s-1
0.47
0.082
Average Luminosity
0.16
0.027
Luminosity Integral /week
pb-1 96 17

5. eRHIC Ring-ring: e-Ring Design
Two 180° arc sections
84 FODO cells with m length
vertical betatron phase advance fixed at 60°,
horizontal betatron phase advance tuneable between 30° to 80°
Dispersion suppressors at each end of an arc
Energy loss per turn for 10 GeV: 10.9 MeV x I (A)
Damping wiggler or super-bend for low beam energy

6. eRHIC Ring-ring: Dynamical Aperture
Momentum acceptance:
At injection: at least 0.5% of injection energy
In the ring: at lease 7 σE
Dynamical aperture: large than 10 σ
Damped energy spread
1x10-3 for 10 GeV
0.5x10-4 for 5 GeV
Dynamical aperture is sensitive to betatron tune working point
Tracking 1024 turns with natural horizontal emittance and half for vertical emittance

7. eRHIC Ring-ring: Other Studies
Beam Instabilities
Single & coupled bunch instabilities, HOM heating, ion related effects, electron cloud
Provide calculation results on inpedance budget, transverse mode coupling instability, longitudinal microwave instability threshold, longitudinal coupled bunch instability, transverse coupled bunch instability, fast beam-ion instability,
Beam-beam issue
Beam polarization
RF in electron ring
Electron cooling

8. eRHIC Ring-ring: Interaction Region
(Blue) ion ring magnets
(Red) electron beam magnets
(Yellow) ion ring magnets
Detector
Yellow ion ring makes 3m vertical excursion.
Design incorporates both normal and superconducting magnets.
Fast beam separation. Besides the interaction point no electron-ion collisions allowed.
Synchrotron radiation emitted by electrons does not hit surfaces of cold magnets

9. eRHIC Ring-ring: IR design Scheme
Distance to nearest magnet from IP
Beam separation
Magnets used
Hor/Ver beam size ratio
Ring-ring,
l*=1m 1m
Combined field quadrupoles
Warm and cold
0.5
Ring-ring, l*=3m 3m
Detector integrated dipole
Linac-ring 5m
Warm 1
No crossing angle at the IP
Linac-ring: larger electron beta*; relaxed aperture limits ; allows round beam collision geometry (the luminosity gains by a factor of 2.5).
Detector integrated dipole: dipole field superimposed on detector solenoid.

10. eRHIC Ring-ring: Interaction Region

11. eRHIC: ERL-Ring

12. eRHIC ERL-Ring: Full Energy

13. eRHIC ERL-Ring: Parameters

14. eRHIC ERL-Ring: Recent Developments
Presentations at Stony Brook EIC Meeting, Jan. 2010

15. Electron Nucleon Collider at FAIR

16. Parameters

17. ENC@FAIR: Interaction Region

18. LHeC: Ring-Ring

20. LHeC Ring-Ring: Interaction Region
foresees simultaneous
operation of pp and ep
J.Dainton et al, JINST 1 P10001 (2006)

21. LHeC: Linac-Ring