The Accumulator/Pre-Booster
Bela Erdelyi
Department of Physics, Northern Illinois University,
and Physics Division, Argonne National Laboratory
Workshop 01/2011
Page 1
Acknowledgements
• Joint Work with
• Shashikant Manikonda (ANL)
• Peter Ostroumov (ANL)
• Sumana Abeyratne (NIU student)
• With assistance from JLab staff (Y. Derbenev, Y. Zhang, G.
Krafft, etc.)
Workshop 01/2011
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ELIC Conceptual Layout
Three compact rings:
• 3 to 11 GeV electron
• Up to 12 GeV/c proton (warm)
• Up to 60 GeV/c proton (cold)
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Accumulator/Pre-Booster Concept
•
•
Purpose:
• Inject from linac
• Accumulate ions
• Accelerate them
• Extract and send to large booster
Concepts:
• Figure-8 shape for ease of spin transport, manipulation and
preservation
• Modular design, with (quasi)independent module design
optimization
• FODO arcs for simplicity and ease of implementation of optics
correction schemes
• No dispersion suppressors
• Matched injection insertion
• Triplet straights for long dispersion-less drifts and round beam
• Matching/tuning modules in between
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Constraints
•
•
•
•
•
•
•
•
•
Figure-8 shaped; circumference 200-300 m
Maximum bending field: 1.5 T
Maximum quadrupole gradient: 20 T/m
Momentum compaction smaller than 1/25
Maximum beta functions less than 35 m
Maximum full beam size less than 2.5 cm, and 1 cm vertically in
dipoles
5m m long dispersion-less sections for RF cavities, electron cooling,
collimation, extraction, and possibly decoupling
Sizable (normalized) dispersion for/at injection
Working point chosen such that tune footprint does not cross low
order resonances (tunability)
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Injection
• Protons (and possibly light ions)
• Stripping injection
• Heavy ions
• Repeated multi-turn injection
• Transverse (horizontal and possibly also vertical)
and longitudinal painting
• Electron cooling for stacking/accumulation
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Heavy-Ion Injection and Accumulation
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Electron Cooling
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Accumulated Beam
• Intensities needed to achieve design luminosity, with
some safety factors included for possible losses
during
• Stripping
• Capturing, re-capturing
• Transfers
• Proton current: ~ 1A (6x1012 total particles in the
ring)
• Heavy-ion current: ~0.5 A (1x1011 total particles in
the ring) => ~10 linac pulses of ~ 250 μs length
(subject to optimization)
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Acceleration
• h=1
• RF swing necessary is [0.4,2] MHz
• 4 kV per cavity
• 50kV/turn => 12-13 cavities
• Synchronous phase ~ -30˚
• 65000 turns for 200MeV -> 3 GeV
• ~100 ms acceleration time
• Allows acceleration with h=2 with the same cavities,
if needed
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LEIR-Type Cavities
•
•
•
•
Finemet cavities
0.5 m long
4kV/cavity
[0.35,5] MHz
frequency swing
• Practically no
maintenance needed
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Extraction and stripping
• Conventional single-turn fast extraction
• To minimize heavy-ion loss, strip once in linac and
once after the pre-booster to maximize fully stripped
fraction
• Advantages:
• Less beam-loss to reach fully stripped state
• Less severe space charge in pre-booster
• Drawback: lose some energy gain
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Layout
To Large Booster
ARC 1
Injection Insertion
section
ARC 3
ARC 2
Beam from LINAC
RF Cavities
Solenoids for Electron Cooling and Decoupling
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Circumference
Total length of the long drifts in the straights = 20m
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Arc 2
Straight 2
Arc 3
Straight 1
Arc 1
Injection
Linear Optics
Optical modules
ARC1&2 FODO
STRAIGHT TRIPLET
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ARC3 FODO
INJECTION INSERT
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Matching/Tuning modules
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Tunability
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Main Parameters
1
2
3
4
5
6
7
8
9
Units
m
deg
10
11
12
12
Circumference
Angle at crossing
Number of dispersive FODO cells (Type I)
Number of dispersive FODO cells (Type II)
Number of triplet cells
Number of matching cells (2 types)
Minimum drift length between magnets
cm
Drift length in the injection insertion
m
Drift lengths between triplets (for RF, extraction, collimation and electron m
cooling)
Beta maximum in X
m
Beta maximum in Y
m
Maximum beam size
cm
Maximum vertical beam size in the dipole magnets
cm
13
14
15
16
17
18
19
Maximum dispersion (x|delta_KE)
Normalized dispersion value at injection insert
Tune in X
Tune in Y
Gamma of particle
Gamma at transition energy
Momentum compaction
Workshop 01/2011
m
m½
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Value
302
44
6
8
18
4
50
5.0
5.3
33
36
2.3
0.6
3.3
2.1
7.92
7.24
4.22
5.6
3.2E-2
Magnets
1
2
3
Quadrupole Magnets
Dipole Magnets (Type I)
Dipole Magnets (Type II)
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Quantit
y
113
Parameters
Units
Value
Length
Half aperture
Maximum pole tip field
Minimum pole tip field
cm
cm
T
T
40
5
1.5
0.15
Strength
Radius
Vertical aperture
Angle
Length
T
m
cm
deg
m
1.41
9.0
3.0
11.6
1.83
Strength
Radius
Vertical aperture
Angle
Length
T
m
cm
deg
m
1.41
9.0
3.0
14.0
2.19
16
18
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20
Beam Parameters at the End of the Pre-Booster Cycle
Proton
Lead
Beam energy
GeV
3
1.18
Particles number
1012
6
0.1
Beam Current
A
1
0.5
Polarization
%
>90% (est.)
N/A
Energy spread
10-4
?
?
Bunch length
m
63
63
Horizontal acceptance, normalized
µm rad
55
28
Vertical acceptance, normalized
µm rad
37
12
0.071
0.015
Laslett tune shift (after injection)
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Pre-Booster Cycle Time
• Assuming 1x1011 lead ions need to be accumulated
• One 250 μs long linac pulse (subject to optimization) delivers ~
0.5 mA
• Assume ~50% injection efficiency (CERN experience)
• => 9 linac pulses
• Cooling time estimated to be ~130ms
• => Total time =
• 9x 250 μs (injection) +
• 9x130 ms (cooling) +
• 2x100 ms (acceleration and de-ramping)
• ≈ 1.4 s
• Assuming factor of 4 ratio between circumferences between
pre-booster and large booster, and acceleration with -30˚ => 16
cycling times needed to fill the large booster => 22s (~3s for p)
• Large booster starts with coasting beam
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Summary and Work in Progress
• Design of the accumulator/pre-booster is well underway
• Satisfies the constraints while providing superior performance
•
•
•
•
Fine tuning first order optics
Space charge simulations; limits on current and emittance
Spin tracking, polarization preservation studies
Dynamic aperture estimation
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BACKUP SLIDES
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Cooling times
•
Assuming:
• 3 m long cooling section
• 300 mA electron current
• 2.5 cm beam radius
• ± 5 mrad beam divergence
• ±0.004 momentum dispersion
• Cooling for 3 time constants
 Transverse cooling time: ~ 130 ms
 Longitudinal cooling time: ~ 67 ms
Cooling electron energies:
• @ injection: { 0.55394 MeV, γ=2.0840 }
• @ extraction: { 1.15511 MeV, γ=3.2605 }
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Lead Charge Distributions
• @ injection
• Q (0)
Q (1) Q (2)
•
0
4%
70%
• @ extraction
• Q (0)
Q (1)
•
80%
20%
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Q (3)
22%
Q (4)
3%
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Shorter Version (C=250m)
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Linear Optics
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Optical Modules
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Main Parameters
Units
m
deg
Value
254
62
6
1
2
3
Total length
Angle at crossing
Number of dispersive FODO cells (Type I)
4
Number of dispersive FODO cells (Type II)
9
5
6
7
Number of triplet cells
Number of matching cells
Minimum drift length between magnets
cm
10
4
50
8
Drift lengths in the insertion region
m
5.0
9
Drift lengths between triplets (for RF, collimation and electron cooling)
m
5.0
10
11
12
Beta maximum in X
Beta maximum in Y
Maximum beam size
m
m
cm
19
34
2.0
12
Maximum beam size in the dipole magnets
cm
0.6
13
Maximum Dispersion (x|delta_KE)
2.5
14
Normalized dispersion value at injection (x|δ_KE)/√β
1.41
15
16
17
18
Tune in X
Tune in Y
Gamma of particle
Gamma at Transition Energy
8.33
7.43
4.22
5.62
19
Momentum compaction factor
0.031
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Magnets
1
2
3
4
Quadrupole Magnet
Dipole Magnet (Type I)
Dipole Magnet (Type II)
Dipole Magnet (Type III)
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Quantity
95
Parameters
Units
Value
Length
cm
Half aperture
cm
Maximum pole tip T
field
Minimum pole tip T
field
40
5
1.5
Strength
Radius
Vertical aperture
T
m
cm
1.41
9
3
Angle
Length
deg
m
14
2.19
Strength
Radius
Vertical aperture
T
m
cm
1.41
9
3
Angle
Length
deg
m
13.17
2.06
Strength
Radius
Vertical aperture
T
m
cm
1.41
9
3
Angle
Length
deg
m
13.44
2.11
0.16
6
12
18
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Laslett Tune Shift (protons)
•
•
•
•
•
•
•
•
Beta=0.57
Gamma=1.21
Nt(total)=5.36E+12
rc = 1.53E-18m
EN(normalized)=Beta*Gamma*9E-6 m.rad
BF=1 (Peak to average current radio)
laslett_tune_shift=-(Nt*rc*Bf)/(4*pi*EN*beta*gamma^2)
laslett_tune_shift=-0.071.
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Laslett Tune Shift (Lead)
•
•
•
•
•
•
•
•
Beta=0.37
Gamma=1.08
Nt(total)=4.33E+10
rc = 1.53E-18m
EN(normalized)=Beta*Gamma*17.5E-6 m.rad
BF=1 (Peak to average current radio)
laslett_tune_shift=-(Nt*rc*Bf*Q^2)/(4*pi*EN*M*beta*gamma^2)*
laslett_tune_shift=-0.015.
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