Beam Dynamics Justification of RF Gun Modifications C.Limborg-Deprey

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Beam Dynamics Justification of RF Gun
Modifications C.Limborg-Deprey

• Dual Feed Racetrack
• Dual Feed
• Racetrack shape
• Beam Dynamics (from PARMELA) for 4 cases
• 2D gt no ports
• Reference case compared with superfish
• 3D gt coupling port but original cylindrical cell
  shape
• Exhibits head-tail quadrupole mode
• 3D gt with racetrack shape in full cell
• Corrects for quadrupole mode effect
• 3D gt with laser ports in ½ cell and racetrack
  shape
• Laser ports do not deteriorate emittance

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Dual Feed
Racetrack shape
Laser ports
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Beam Dynamics, Nominal tuning 1nC, 10ps
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Dual Power Feed

• Symmetrization of field see D.Palmer, R.Miller
  et al. SLAC PUB 95-6799
• ?? Corrects for amplitude term but not for phase
  term

• Assumption head-tail kick from phase term

• ?twiss 7 m
• on 3.10-6 m.rad
• ? 12

• Can be corrected partially by using the
  transverse wakefield in L01
• But, not convenient since
• Charge, bunch length dependent
• Offset in GunToLinac introduces other
  transverse wakefields

• Will be confirmed with Computations (upgrades of
  Omega3P)

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Suppression of quadrupole head-tail with the
racetrack shape of the full cell
No coupling ports
With coupling ports
Slice emittance along the bunch (100 slices) at
the end of L02
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• Retuning the beamline for the full map
• ( map including racetrack plus laser ports)
• Egun field close to optimum
• Solenoid field reduced by 1
• ??RF decreased by 2degrees

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Full Map Including, laser ports in ½ cell
racetrack in full shape ?x,80 0.908
mm.mrad ?y,80 0.915 mm.mrad
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Conclusion

• Dual Power Feed
• perfect symmetry
• still to be justified with numerics
• Racetrack shape
• importance demonstrated
• Laser ports
• Do not affect dynamics