Injection System with a Booster in Separate Tunnel

1
Injection System with a Booster in Separate
Tunnel

• T. Shaftan
• for the NSLS-II team

2
Outline

• Summary of NSLS-II injection requirements
• Ring injection straight
• Injection simulations
• New injector layout
• 200-MeV linac
• 3.0-GeV booster
• Injector tunnel
• Challenges
• Conclusion

3
Summary of NSLS-II injection requirements

• High reliability
• Reasonable initial fill time
• Low losses
• Low power consumption
• Lifetime 3 hours (with 3rd HC)
• Top-off
• Stability of current lt1
• Time between top-off injections gt1 min
• Bunch-to-bunch variations of charge lt20
• Storage ring 7.3 nC per 1 min top-off format
  1-2 shots per 1 min
• Linac 15 nC in 1 min (50 losses), THALES linac
  9.3 nC/300 ns
• Bunch train 80 300 ns long (40 150 ring
  buckets)

I
t
I
t
QI
t
Ib
bunch
4
Injection straight-section
Closed bump design

• Closed non-interleaved bump design
• Fits into a single straight section of the ring
• 2-turn long pulsed kickers
• Optimization of the injected beam Twiss
  parameters
• Sufficient tolerances for injected and stored
  beam
• Minimization of injection transients effect on
  stored beam

Injection geometry near septum
3 mm
Septum knife
I
stored beam
?kicker
t
10?stor 2 mm COE
1st turn
2nd turn
3rd turn
3?inj
4 mm
with I. Pinayev, R. Heese
5
Simulations of injection into the ring

• 200 particles, 10000 turns
• RF is ON, synch rad is ON
• Transverse misalign. are ON
• Multipole field errors
• Realistic apertures included
• Orbit correction
• Tune correction
• Coupling correction (in TRACY-2)
• Injected beam with optimum beta-functions
• No IDs yet
• Injection tracking with emittances of 35 at 3
  GeV
• No limitations from DA (DA is larger then vacuum
  chamber size)
• Sufficient tolerances for injection into the
  ring are observed

Courtesy of L.H. Yu and I. Pinayev
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Injector layout with compact booster

• ASAC-2006 in-tunnel booster
• Lehman Review 2007 recommendation for choosing
  compact booster
• Diamond, Soleil, BESSY, APS, ALS,
  low-emittance solution ASP booster
• Reworking the ASP booster lattice headroom for
  3.6 GeV
• Minimum of modifications cost-effective solution
• Higher current (30 mA), longer bunch trains,
  injection at 200 MeV

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200-MeV linac

• 3-GHz 100-MeV linac from THALES is in operations
  at SOLEIL
• SOLEIL gun operates at 352 MHz, we need 500 MHz
• We need 15 nC in 80-300 ns at 200 MeV
• Assume 50 losses in the booster-ring bucket
• Higher energy reduces beam loading and energy
  spread, eases booster injection
• Higher energy provides with redundancy loss of a
  klystron ? booster injection at 177 MeV
• Need for flexible bunch train format

from HELIOS, THE LINAC INJECTOR OF SOLEIL
INSTALLATION AND FIRST RESULTS, PAC-2005
Measured beam trains in LPM (SOLEIL)
J. Rose
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3 GeV booster

• NSLS-II Booster parameters
• Emittance 35.2 nm (at 3 GeV)
• Circumference 143.96 m
• Tunes 10.3/3.27
• Chromaticity 10.41/13.27
• Momentum Compaction 0.0081
• Loss per turn 625 keV
• Damping times x/y/E, 5.0/4.6/2.2 ms
• Energy spread/Bunch length 0.078/14 ps
• RF Voltage 1.2 MV
• Beam current, 31 mA
• Combined-function FODO
• 32 BDs and 28 BFs

½ of booster lattice
with W. Guo, J . Skaritka, R. Maier
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Injector tunnel

• Tunnel of 150m circumference
• Same elevation as storage ring
• Earthen berm on top and sides
• Lower level accelerators
• Upper level service areas, power supplies, RF,
  vacuum supplies, controls
• Injector building may be shifted by 1 superperiod
  clockwise
• Total injection system power consumption
• 600 kW at 1 Hz
• 200 kW in top-off

Lower level
Upper level
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Challenges

• Evaluation of losses at booster injection
• Passing long bunch trains through the injector
  (flat-top of kickers)
• Hunt and peck mode of injection
• Single-bunch versus multi-bunch for complex bunch
  patterns
• Minimization of injection transients in stored
  beam
• Closing injection bump (feedback with additional
  weak kickers)
• Individual versus in-series PS for kickers for
  reduction of injection transient

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Conclusions

• Injector with compact booster is under
  development
• 200-MeV linac will provide with high charge per
  pulse in flexible bunch trains
• Low emittance booster lattice is chosen (35 nm at
  3 GeV, 49 nm at 3.6 GeV), supported by
  simulations of injection process into Storage
  Ring TRACY-2 and ELEGANT
• Linac and booster ring (w/o RF) are turn-key
  procurements with some modifications from
  original design transport lines and injection
  straight section by BNL
• Increase in injector cost (7 M) due to the
  booster building

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Future work

• Refinement of ring injection tracking (including
  IDs, 3.6 GeV, etc.),
• simulations of injection into the booster at low
  energy,
• evaluation of losses throughout injector,
• short bunch train analysis (beam loading),
• minimization of transients in the ring injection
  straight design,
• availability analysis.