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The Accumulator/Pre-BoosterThe Accumulator/Pre-Booster

Bela Erdelyi Department of Physics, Northern Illinois University,and Physics Division, Argonne National Laboratory

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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.)

• 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.)

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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

ARC 1

Injection Insertion section

ARC 2

Non dispersive section 1

ARC 3

Non dispersive section 2

RF Cavities

Electron Cooling

Solenoids for Electron Cooling and Decoupling

ExtractionCollimation

Beam from

LINAC

To Large Booster

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Circumference

Total length of the long drifts in the straights = 20m

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Linear Optics

Inje

ctio

n

Arc

1

Str

aig

ht

1 Arc

3

Str

aig

ht

2 Arc

2

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Optical modules

ARC1&2 FODOARC3 FODO

STRAIGHT TRIPLET INJECTION INSERT

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Matching/Tuning modules

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Tunability

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Main Parameters Units Value

1 Circumference m 3022 Angle at crossing deg 443 Number of dispersive FODO cells (Type I) 64 Number of dispersive FODO cells (Type II) 85 Number of triplet cells 186 Number of matching cells (2 types) 47 Minimum drift length between magnets cm 50 8 Drift length in the injection insertion m 5.09 Drift lengths between triplets (for RF, extraction, collimation and electron

cooling)m 5.3

10 Beta maximum in X m 3311 Beta maximum in Y m 3612 Maximum beam size cm 2.312 Maximum vertical beam size in the dipole magnets cm 0.6

13 Maximum dispersion (x|delta_KE) m 3.314 Normalized dispersion value at injection insert m½ 2.115 Tune in X 7.9216 Tune in Y 7.2417 Gamma of particle 4.2218 Gamma at transition energy 5.619 Momentum compaction 3.2E-2

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Magnets

Quantity

Parameters Units Value

1 Quadrupole Magnets 113Length cm 40

Half aperture cm 5Maximum pole tip field T 1.5

Minimum pole tip field T 0.152 Dipole Magnets (Type I) 16

Strength T 1.41Radius m 9.0

Vertical aperture cm 3.0Angle deg 11.6

Length m 1.833 Dipole Magnets (Type II) 18

Strength T 1.41Radius m 9.0

Vertical aperture cm 3.0

Angle deg 14.0Length m 2.19

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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

Laslett tune shift (after injection) 0.071 0.015

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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

• 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) Q (3) Q (4)• 0 4% 70% 22% 3%

• @ extraction• Q (0) Q (1)• 80% 20%

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Shorter Version (C=250m)

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Linear Optics

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Optical Modules

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Units Value1 Total length m 2542 Angle at crossing deg 623 Number of dispersive FODO cells (Type I) 6

4 Number of dispersive FODO cells (Type II) 9

5 Number of triplet cells 106 Number of matching cells 47 Minimum drift length between magnets cm 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 Beta maximum in X m 1911 Beta maximum in Y m 3412 Maximum beam size cm 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 Tune in X 8.3316 Tune in Y 7.4317 Gamma of particle 4.2218 Gamma at Transition Energy 5.62

19 Momentum compaction factor 0.031

Main Parameters

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    Quantity Parameters Units Value1 Quadrupole Magnet 95            Length cm 40      Half aperture cm 5      Maximum pole tip

fieldT 1.5

      Minimum pole tip field

T 0.16

2 Dipole Magnet (Type I) 6            Strength T 1.41      Radius m 9      Vertical aperture cm 3

      Angle deg 14      Length m 2.193 Dipole Magnet (Type II) 12            Strength T 1.41      Radius m 9      Vertical aperture cm 3

      Angle deg 13.17      Length m 2.064 Dipole Magnet (Type III) 18            Strength T 1.41      Radius m 9      Vertical aperture cm 3

      Angle deg 13.44      Length m 2.11

Magnets

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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.