Bunch Cleaning System

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Bunch Cleaning System
Fernando Sannibale W. Barry, W. Byrne, M. Chin,
R. Duarte, H. Nishimura, J. Oneill
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Contents
ALS Topoff Upgrade 1st Project Review November
23, 2004

• Motivation Considerations
• Proposed Bunch Cleaning System
• Storage Ring Cleaning System Upgrade
• Storage Ring Bunch Purity Monitor

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Motivation Considerations
ALS Topoff Upgrade 1st Project Review November
23, 2004

• Experiments with long relaxation time
• Top journals publications
• 4 weeks/year two bunches mode.
• (Distance between bunches 330 ns)
• Actual cleaning system exploits tune shift with
  current
• Non compatible with top-off
• Proposed system cleaning in the booster

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Bunch Cleaning System Scheme
ALS Topoff Upgrade 1st Project Review November
23, 2004
Betratron sideband frequency
Bunch selector signal (synch. with RF)

• Light sources using or testing such a scheme
• APS
• Spring 8
• ESRF
• Successful test at the ALS storage ring

N. Sereno, Proceedings of the 1999 Particle
Accelerator Conference, New York, US, 1999, p.
2322. H. Suzuki, et al., Nuclear Instruments and
Methods in Physiscs Research A 444 (2000)
515-533. T. Aoki, et al., Proceedings of the 2003
Particle Accelerator Conference, Portland, US,
May 2003, p. 2551. E. Plouviez, ESRF Machine
Technical Note 01-04/MDT.
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Bunch Cleaning System Basics
ALS Topoff Upgrade 1st Project Review November
23, 2004
H. Suzuki, et al., Nuclear Instruments and
Methods in Physiscs Research A 444 (2000) 515-533.
ALS stripline transverse kicker
Electrode length (l) 30 cm Electrode diameter (d) 70 mm
Electrode subtend angle (DF) 120 deg Characteristic impedance (ZL) 50 W
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Booster Cleaning Systems
ALS Topoff Upgrade 1st Project Review November
23, 2004
Cleaning in the Booster during energy ramping 1
ms cleaning is sufficient, 10 ms is safer
Beam energy at cleaning 300 MeV Natural vertical chromaticity - 4.61
Booster revolution period (T0) 250.2 ns Operation vertical chromaticity 0.0 0.1
RF frequency 500 MHz Vertical Tune 2.72
Harmonic number 125 Vert. excitation frequency 1.12 MHz
Long. Damp. time _at_ 300 MeV 400 ms Max tune variation at DE/E  0.5 (Dny) 5 10-4
Transv. damp. time _at_ 300 MeV (td) 800 ms Vertical kick angle (Dq) 6.3 mrad
Vertical beta function at scraper position (bSc) 10 m Kicker type stripline
Vertical beta function at the kicker position (bK) 10 m Kicker shunt impedance 9000 W
Distance vertical scraper-reference orbit (Dy) 10 mm Amplifier power (P) 200 W
Energy spread at 300 MeV (rms) (1 rms linac energy spread _at_ 50 MeV) 1.710-3 Amplifier bandwidth gt 200 MHz
SR Transverse feedback amplifiers match the
requirements
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Booster Cleaning System
ALS Topoff Upgrade 1st Project Review November
23, 2004
Vertical kicking allows leaving scraper in during
Booster injection
Kicker and scraper can be in different periods
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Storage RingCleaning System Upgrade
ALS Topoff Upgrade 1st Project Review November
23, 2004

• In some conditions, a high purity injection
  alone could not be sufficient.
• If the dynamic aperture of the storage ring is
  larger than the RF bucket size, diffusion from
  the main bunches to the near ones can happen.
• In such a case, a periodic cleaning in the
  storage ring will be required as well.
• We propose to include in the storage ring a
  cleaning system similar to the one in the
  Booster.
• The more expensive system components are already
  present in existing subsystems in the ring.
• The system will use the existing transverse
  feedback system amplifiers and kickers jointly
  with the existing vertical scraper.
• An additional arbitrary function generator is
  required

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Storage RingBunch Purity Monitor
ALS Topoff Upgrade 1st Project Review November
23, 2004

• Visible and x-ray Options
• Visible gated MCP PMT, max resolution 10-4
• Easier to implement - cheaper
• X-rays APD, max resolution 10-7
• New port is required - more expensive