XFEL Photo Injector Simulations

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XFEL Photo Injector Simulations

• M.Krasilnikov, PITZ

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XFEL Photo Injector Layout
Superconducting TESLA module (ACC1)
RF gun

• Injector parameters to be optimized
• Cathode laser XYrms, (Trms)
• RF-Gun launch RF phase
• Solenoid position, peak field (current)
• Booster position, gradient, RF phase

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XFEL Photo Injector Simulations
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XFEL Photo Injector Simulations
Beam transverse rms size and normalized emittance
proj.emittance 0.87 mm mrad
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XFEL Photo Injector Simulations
Beam energy and rms energy spread
Longitudinal emittance and bunch rms length
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XFEL Photo Injector Simulations
Influence of thermal emittance from the photo
cathode
Normalized transverse emittance after XFEL
injector as function of the initial kinetic
energy of the photo emitted electrons
Slice emittance _at_z18m
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Dependence on Gun Gradient (PITZ case)
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Solenoid Position
z0.276m
z0.41m
New solenoid position requires modification of
the input coupler (increased length of coaxial
part).
What can be achieved with actual solenoid
position?
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Change the Optimization Procedure
Cathode laser (XYrms, Trms) gun parameters
(RF Phase, Imain, sol.pos)
Emittance
0 step. tune the bunch charge
Qbunch-gtQ1nC(_at_z5cm) Emission effects (SC,
Schottky)
Xrms,Xemit
1 step. Run ASTRA till z5m
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Re-Optimization (Actual Solenoid Position)
Also the current solenoid z-position is OK
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Cathode Laser Ellipsoid Vs. Cylinder
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XFEL Injector Simulations Outlook

• Studies of tolerances for cathode laser
  parameters FWHM, rise/fall time, flat-top
  modulation
• Influence of the vacuum components (like a vacuum
  mirror, diagnostic cross etc) on the beam quality
• Impact of photo injector imperfections
  (misalignment)