Latest results from the Swiss Light Source

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Latest results from the Swiss Light Source

• Andreas Streun
• Paul Scherrer Institut, Villigen, Switzerland
• ESLS XVI, Daresbury, Nov. 27-28, 2008

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Completion of the SLS
17 user beam lines in 2010
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(No Transcript)
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The SLS storage ring

• 2.4 GeV, 288 m circumference, 12 ? TBA (8º14º
  8º)
• 6 4 ? 4 m, 3 2½ ? 7 m, 3 2 ? 11.5 m user
  straights
• Emittances ey 5.0...6.8 nm rad, ey 3...10 pm
  rad
• Current 400 ? 1 mA (top-up), beam lifetime 5..10
  hrs

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Operation statistics
A. Lüdeke
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Main problems in 2008

• 50 kV transformer breakdown
• 1 week operation at reduced current 170 mA with
  warm 3rd harmonic s.c. cavity.
• RF cavity / coupler water leaks
• Storage ring 3 leaks water ? air.(25 hrs
  downtime)
• Booster 1 leak water ? vacuum.(92 hrs
  downtime)
• Measures
• improvement of water quality.
• reduction of water flow rate.
• planning for exchange of cavities.

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The booster water leak
3 liters of water in the cavity
Water leak
Hole ca. 50µm diameter
Cavitation and corrosion
L. Stingelin
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SLS Performance upgrade

• RF upgrade rejected
• BPM system upgrade ? 2014
• Arbitrary filling patterns done
• Low alpha operation started
• Coupling control in progress
• Lifetime improvement in progress
• Rounder beams started

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RF upgrade

• replace 4 Cu-cavities by 1 s.c. cavity
• ? one more straight for a new undulator beam line
  !

presentsituation
upgradescenario
L. Stingelin
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RF upgrade

• Problems with Cu-cavities (leaks, HOMs...) ?
  replace by 1 or 2 s.c. cavities (V2 MV)
• He-liquifier for 3HC needs upgrade anyway? big
  common liquifier for new cavity and 3rd HC
• LUCIA beam line (½7M) moved to SOLEIL (2008)?
  new BL PHOENIX (2009) ? 8S, all RF ? 7M
• concerns about reliability of s.c. cavity
• no budget for another undulator beam line
• s.c. upgrade scenario rejected
• replacement of Cu-cavities by same type (2010?)

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BPM system upgrade

• Very good performance of present system 300 nm
  rms orbit in straights, 100 Hz feedback.but gt
  s/10 for very low coupling.
• Typical system lifetime 15 years. Design
  1999.? plan for replacement now.
• New system as spin off from ongoing works for
  EUROFEL/PSI-XFEL systems.
• Factor 2-3 in performance expected 100 nm rms
  orbit in straights, 2-300 Hz feedback.
• replacement until 2014.

B. Keil, T. Schilcher, V. Schlott
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Arbitrary filling patterns

• Filling pattern feedback operational
• single bunch current measurement (APD).
• single bucket selection for injection.
• Planned FEMTO upgrade(FEMTO 150 fs FWHM X-ray
  pulses from laser beam slicing)Laser repetition
  rate 2 ? 10 kHz gtgt(damping time)-1
• avoid increased halo background. ( linear with
  rep. rate)
• alternating shots with/without laser. (?
  background subtraction)
• constant time intervals.(beam loading ? phase
  shift)
• period-3 or -5 filling.

B. Kalantari
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Low alpha operation

• SLS rms bunch length ss/c
• 40 ps at 400 mA 3HC normal operation.
• 0.06 ps at low flux (105 g/s) FEMTO.
• 16 ps at lt200 mA, 3HC off natural.
• 8 ps, 50 mA some users are interested.
• 4 ps at 5 mA tested.?

a-tuning by ? negative dispersion in TBA centre
THz power vs. beam current?
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Coupling control and lifetime improvementVersatil
e sextupoles

• 120 sextupoles in 9 families
• SF(24), SD(24), SE(24) ? chromaticities
• SSA(12), SSB(12), SMA(6), SMB(6), SLA(6), SLB(6)
  ? D.A.
• SD, SE, S?B 72 hor. vert. correctors ? orbit
  control
• S?A 24 skew quads (h0) ? betatron coupling
• SF 6 skew quads (hgt0) ? vertical
  dispersion 6 auxiliary sextupoles ? resonance
  suppression (12 still available)

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Coupling control

• High resolution beam size monitor. ?Å.
  Andersson et al., NIM A 591 (2008) 437
• Suppression of hy by hx gt 0 skew quads. ?
• Suppression of Qx?Qyby hx 0 skew quads.
• Lowest V-emittance ey2.8 (? 0.4) pm rad
  (coupling 0.05 ).
• adjust ey ? T for users.

M. Böge, Å. Andersson
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Lifetime improvements

• Modes h of the sextupole Hamiltonian
• Sextupole families
• Im (h) 0 by lattice symmetry
• optimized for Re (h) ? 0 ? h .
• Auxiliary sextupoles
• compensate parasitic Re,Im (h) ? 0.
• empirical optimization.
• 30 Lifetime increase.
• (strength 3 of main sextupoles.)

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Energy acceptance recovery

• Skew quadrupoles
• auxiliary sextupoles...
• ... off (ey/ex 0.22)
• ... optimized (ey/ex 0.14)
• (polynomial fit, unphysical)
• theory (linear lattice)
• Lattice energy acceptance ? 3 ?

T ? Ibunch / sy mA h /mm
RF voltage MV
preliminary data, Nov.25,2008
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Rounder beam

• mismatch
• flat beam (aspect ratio 130...40)
• approx. round sample ?

• by? bx? in straights
• ? brightness (16 keV, L2m)

3 / -3 Dp/p
better working point F6C ? F9C, robust
100 injection efficiency ?
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Conclusion

• Status of SLS after 7 years of operation
• delivered 35000 hrs of user beam time.
• close to final stage of extension.
• proven to be of just the right size.
• starts to feel the process of aging.
• accelerators fulfill/exceed all specs.
• still room to upgrade performance.