# Presentation: 518528

## Injection System with a Booster in Separate Tunnel 

- T. Shaftan
- for the NSLS-II team

## 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

## 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 <1 %
- Time between top-off injections >1 min
- Bunch-to-bunch variations of charge <20%
- 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)

- Ī

- t

- Ī

- t

- QI

- t

- Ib

- bunch #

## Injection straight-section

- 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

- Septum
- “knife”

- I

- 3inj

- 4 mm

- 10stor+
- +2 mm COE

- 3 mm

- Closed bump design

- Injection geometry near septum

- stored
- beam

- t

- 1st turn

- 2nd turn

- 3rd turn

- kicker

- with I. Pinayev, R. Heese

## Simulations of injection into the ring 

- Courtesy of L.H. Yu and I. Pinayev

-  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

## 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

## 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

| Measured value | LPM | SPM |
| --- | --- | --- |
| Pulses | 100 | 4 |
| Pulse length, ns | 286 | 1.3 |
| Energy, MeV | 108 | 110 |
| Charge, nC | 9.3 | 2.15 |
| Emittance X/Y, μm (4’)   | 47/52 | 67/78 |
| Energy spread, % | 0.5 | 0.82 |

- Measured beam trains in LPM (SOLEIL)

- from: HELIOS, THE LINAC INJECTOR OF SOLEIL:
- INSTALLATION AND FIRST RESULTS, PAC-2005

- J. Rose

## 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

- 1⁄2 of booster lattice

- with W. Guo, J . Skaritka, R. Maier

## 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

- 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

- Injector tunnel

## 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

## 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

## 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.