William M. Fawley

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William M. Fawley Lawrence Berkeley National
Laboratory Presented to LCLS Undulator Parameter
Workshop24 October 2003
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Outline of GINGER Study

• First determine best K for peak gain for
  monochromatic cases at l1.5, 0.15, and 0.1 nm
• Examine taper performance for SASE runs at
  0.15-nm, 11.47 GeV base case
• SASE performance at 0.1 nm with E14.04 GeV
• Study of taper sensitivity for 1.5 nm case
• No wake effects examined --- need ELEGANT
  time-dependent beam parameters
• Some additional S2E SASE results for ICFA03 study
  envelope reconstruction looks surprisingly good

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Study Parameters/Bottom-Line Results
SASE results best taper for 0.15, 1.5 nm
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Effects of Linear K Taper on LCLS SASE Output
Power at ?0.15nm

• GINGER SASE runs
• New drift space/undulator configuration
• Quadrupole strengths Twiss parameters from
  H.-D. Nuhn
• Taper begins at z75 m simple linear decrease
  with z (including drift spaces)
• Max power obtained around 0.3 to 0.4 taper
  excessively large tapers appear to lead to rapid
  debunching with z and thus reduced gain

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Bunching and Inverse Bandwidth vs Z0.15-nm LCLS
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SASE Results at 0.1-nm Wavelength

• No taper
• 1st saturation at 110 m
• Output power 6 GW
• No obvious anomalies ---but little margin for any
  beam degradation

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1.5-nm Taper Results

• 1.5 nm option is a cake-walk for LCLS
  parameters
• 1st saturation at 30 m simple linear tapering
  begins at z25 m
• Tapering increases power over 6-fold to gt 80 GW
• 60 m of undulator gives most of output power
• More intelligent tapers probably could increase
  power to gt100 GW

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New GINGER Results for ICFA03 2nd-Order
Simulation Study

• Extension of results for ICFA03-Zeuthen S2E study
  for LCLS
• Full SASE simulation extended over full beam head
  region- results low-pass filtered in time
  (original res-olution 12 attoseconds)
• In regions where 5D distribution is simple,
  full SASE and envelope reconstruction agree
  surprisingly well
• Similar runs underway for wake case

(CSR but no wake fields)
Output P for SASE peak P(z) for no slippage
cases
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Where might we go from here?

• Need ELEGANT runs with/without CSR effects to
  produce time-dependent 5D distributions at
  undulator entrance
• Examine temporal sensitivity of P(z) to taper
• Examine
  to wakes
• One optimization criterion is maximizing product
  of power times the inverse bandwidth (at least
  for experiments in which monochromatization will
  be done)
• See if results with taper are more sensitive to
  undulator errors, beam offset/pointing errors
• Perhaps greater sensitivity to phase jitter but
  does deeper ponderomotive well help?
• Develop taper algorithm for undulator with drift
  spaces consider effects of spiky SASE P(t)