Berkeley Lab Generic Presentation

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Optics for ELIC - Collider Rings and Interaction
Region Design
Alex Bogacz Center for Advanced Studies of
Accelerators
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ELIC Ring-Ring Collider - Design Choices

• Figure-8 Collider Ring Topology
• Ensures spin preservation and ease of spin
  manipulation (spin rotators)
• Removes spin sensitivity to energy for all ion
  species
• Arc Optics Features
• Minimized emittance dilution due to quantum
  excitations (leptons)
• Limited synchrotron radiated power (leptons)
• Small momentum compaction to alleviate bunch
  lengthening (both species)
• Aggressive Interaction Region (IR)
• Vertically crossing rings - crab crossing
• Ultra small beta Interaction Point (IP)
• Dipole second IR configuration (D 0, D ? 0)

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ELIC Interaction Region Challenges

• Unprecedented high Luminosity 7.81034 cm-2
  s-1 (peak luminosity per IP)
• Enabled by short ion bunches (sz 5 mm), low
  beta ß 5 mm), high rep. rate (1.5 GHz)
• Crab Crossing required to alleviate luminosity
  reduction and to avoid parasitic beam-beam
  interaction due to high repetition rate
• Multiple IRs (4)
• Chromatic compensation with sextupoles necessary

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Figure-8 Rings - Vertical Stacking
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Figure-8 Rings - Vertical Stacking
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Figure-8 Rings - Vertical Stacking
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Figure-8 Ring with 800 crossing
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Figure-8 Ion Ring (half) - Lattice at 225 GeV
8 empty cells
8 empty cells
3 transition cells
3 transition cells
30 full cells
Arc dipoles Lb210 cm B80.6 kG Arc
quadrupoles Lb100 cm G 7.6 kG/cm
phase adv./cell (Dfx 600, Dfy600)
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Figure-8 Ion Ring (half) - Lattice at 225 GeV
phase adv./cell (Dfx 600, Dfy600)
8 empty cells
8 empty cells
3 transition cells
3 transition cells
30 full cells

• Minimum dispersion lattice (periodic)
• Dispersion suppression via missing dipoles
  (geometrical)
• Uniform periodicity of Twiss functions (chromatic
  cancellations)
• Dispersion pattern tailored to chromaticity
  compensation with sextupole families
• One family every third cell (3 600 1800)

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Figure-8 Electron Ring (half) - Lattice at 9 GeV
22 empty cells
22 empty cells
28 superperiods (3 cells/superperiod)
Arc dipoles Lb300 cm B2.7 kG Arc
quadrupoles Lb30 cm G 4.3 kG/cm
phase adv./cell (Dfx 1200, Dfy1200)
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Figure-8 Electron Ring (half) - Lattice at 9 GeV
phase adv./cell (Dfx 1200, Dfy1200)
22 empty cells
22 empty cells
28 superperiods (3 cells/superperiod)

• Minimized emittance dilution due to quantum
  excitations (emittance disp. inv. H)
• Limited (manageable) synchrotron radiated power

Equilibrium Emittance (1200 FODO)
Synchrotron Radiated Power 14.3MW (total)
10.4kW/m _at_ 1.85A
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Figure-8 Electron Ring (half) - Lattice at 9 GeV
phase adv./cell (Dfx 1200, Dfy1200)
22 empty cells
22 empty cells
28 superperiods (3 cells/superperiod)
Momentum Compaction

• Quasi isochronous arc to alleviate bunch
  lengthening
• Dispersion pattern tailored to chromaticity
  compensation with sextupole families
• One family every third quad (3/2 1200 1800)

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Figure-8 Rings - Vertical Stacking
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Figure-8 Straights with two IPs
Note dimension of the drawing not to scale
Minimizing crossing angle reduces crab cavity
challenges and required RD

• 85 m free space to accommodate e/p
  injection/ejection, SRF cavity, electron cooling,
  and electron polarimeter

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IR design with interleaved FF quads
0.2m
0.5m 3.2kG/cm
22.2 mrad 1.27 deg
3.8m
0.6m 2.55kG/cm
10cm
8.4cm
IP
1.8m 20.8kG/cm
3m 12KG/cm
22.9cm
Vertical intercept
Vertical intercept
16.2cm
14.4cm
4.5m
Vertical intercept
electron
4mm
5mm
ion
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Lambertson quad for the final focus
B-Field in coil and force collar
following talk by Paul Brindza
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Crab Crossing - Multi-cell SRF cavities
K. Oide
Crab Cavity requirement for 22 mrad
crossing Electron 1.2 MV (KEK, single
cell, 1.4 MV) Ion 24 MV (multi-cell
cavity, RD raquired)
KEK B-Factory Crab Cavity - Squashed cell
cavity _at_ TM110 B field
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Final Focus Optics - Beam envelopes
Eelectron 9 GeV b 5/5 mm eN 90/3.6 mm
rad
bmax 3.1/32 km
smax 4.0/2.4 mm
Quads Lcm GkG/cm 50 3.2 60 -2.6 80 3.9 80
3.9
350 cm
350 cm
380 cm
220 cm
100 cm
380 cm
220 cm
100 cm
Eion 225 GeV b 5/5 mm eN 1.3/0.06 mm rad
smax 5.0/3.8 mm
bmax 4.8/54 km
Quads Lcm GkG/cm 180 20.8 300 -12.0 200
23.0 200 -22.0
350 cm
350 cm
450 cm
450 cm
100 cm
50 cm
100 cm
50 cm
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IR - Matching to the Ring
Eele 9 GeV
bx,ymax 3.1/32 km
bx,y 5 mm
3.8 m
FF doublet
FF doublet
matching singlet-doublet
FODO
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IR - Matching to the Ring
Eele 9 GeV
bx,ymax 3.1/32 km
bx,y 5 mm
3.8 m
FF doublet
FF doublet
matching singlet-doublet
FODO
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IR - Matching to the Ring
Eele 9 GeV
bx,ymax 3.1/32 km
bx,y 5 mm
3.8 m
FF doublet
FF doublet
matching singlet-doublet
FODO
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IR - Matching to the Ring
Eele 9 GeV
bx,ymax 3.1/32 km
bx,y 5 mm
3.8 m
FF doublet
FF doublet
matching singlet-doublet
FODO
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IR Beta Chromaticity
IR Ions
IR elactrons
Dp/p 0, 0.0001,.., 0.0005
following talk by Hisham Sayed
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Spin rotators - Electron Ring at 9 GeV
empty straight cells
full bending cells
Solenoid magnet Lb300 cm B100 kG
following talk by Pavel Chevtsov
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Spin rotators - Electron Ring at 9 GeV
empty straight cells
full bending cells
Skew Quads Lb90 cm G0.18 kG/cm
decoupled spin rotator module
EIC Collaboration Meeting, Hampton University,
May 19-23, 2008
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Conclusions

• Compelling case for High Luminosity ELIC
• Based on present assumptions 1035 cm-2 s-1
  luminosity collider is feasible more studies
  needed
• Optics - Conceptual lattice design of major
  sub-systems
• Interleaved Interaction Regions for both species
• Figure-8 Arc lattices
• Matching between sections
• Compact Spin rotator Optics
• Still to come.
• Chromatic compensations, higher order effects
• Complete spin matching Optics (IR-to-IR)