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Fluctuations Study Update. A. Lutman. Model description. Undulator section II 1D FEL code Keeps electron slice bunch energy, slice energy spread, or averages Uses as seed the forward Bragg diffracted beam Tapered / untapered operation. Undulator section I 1D FEL code - PowerPoint PPT Presentation
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Fluctuations Study Update
A. Lutman
Magnetic chicaneUndulator section IIUndulaor section I
Crystal
Model description
Undulator section I
• 1D FEL code• Bunch shape: flat top
Short Bunch
Long Bunch
length 20 fs 50 fs
current 2 kA 2 kA
Central energy
13695 13695
Central energy deviation
rho(5x10^-4)
rho(5x10^-4)
Uncorr. en. spread
0.2 rho 0.2 rho
Undulator section II
• 1D FEL code
• Keeps electron slice bunch energy, slice energy spread, or averages
• Uses as seed the forward Bragg diffracted beam
• Tapered / untapered operation
Crystal
• Uses Yuri Shvid’ko time-domain formula for transmitted bragg radiation (Spatiotemporal response of crystals in x-ray Bragg diffraction P.R. ST AB 2012)
• Crystal thickness 104 um
• 004, symmetric Bragg @8333 eV
Undulator section I simulation
s [um]
intensity
Relative slice energy(units of rho)
slice uncorrelated energy spread(units of rho)
s [um]
s [um]
Undulator section I simulation
z [m]
Average Power (logscale)
z [m]
Uncorrelated average energy spread
Diamond = chicane and crystal location
Monochromatic Wake After Crystal
s [um] s [um]
forward Bragg diffraction point response function
Convolution with seed and electron bunch
delayed
Monochromatic Wake After Crystal
s [um]
Some single shotsAverages around different energies
s [um]
W W
Monochromatic Wake After Crystal
W
P(W)
W
Beam energy [MeV]
Monochromatic Wake After Crystal (Long Bunch)
s [um] s [um]
phaseW
AverageSingle shot
Untapered Radiator – Short Bunch case
z [m] z [m]
W W
Single-Shot growth curve average growth curve
All photon energies1 eV bandwidth
Untapered Radiator – Short Bunch case
Time domain (horizontal axis s [um],vertical axis power [W])
10m 20m 30m
40m 50m 60m
Untapered Radiator – Short Bunch case – single shot spectra
eV
eV
eV
eV
Untapered Radiator – Short Bunch case – in 1 eV photon energy
Horizontal: ebeam energy, vertical intensity
10m 20m 30m
40m 50m 60m
All-energies All-energies All-energies
Untapered Radiator - in 1 eV – Short Bunch (fixed e beam energy)
@ 0 m
@ 0 m @ 0 m
@ 0 m
@ 10 m @ 30 m
@ 50 m @ 70 m
Untapered Radiator – Short Bunch case – in 1 eV
10 MeV beam energy
z [m]
Tapered Radiator
1 eVAll ph.en.
z [m]
Average Power (logscale)
3-single shot spectra
eV
eV
eV
Tapered Radiator – Short Bunch case
20m 30m 40m
50m 60m 70m
1 eVHorizontal: ebeam energy, vertical intensity
Tapered Radiator – Short Bunch case
Relative energy rms 7.2 x 10-4
Experimental DataKmono measurement 05/15/2012
Fluctuations 72%
Simulation
Relative energy rms 5 x 10-4 Fluctuations 67%
Rho = 5 x 10-4
Fit rms3.5 x 10-4
Rho = ~7 x 10-4
Tapered Radiator - fluctuations
z [m]
std/avg
Conclusions
Agenda
• Long bunch case (delay ?)• 111 Asymmetric Laue reflection• Changing chicane position
• Seed intensity is not gamma distributed for narrow electron beam energy filtering
• Position of bumps dependent on single shot realizations• Simulation represents well spectral substructures in self-seeded
spikes• Starting with higher seed intensity does not mean reaching
higher intensity: beam energy, uncorrelated energy spread, “bumps” position matter more
• Simulation shows lower fluctuation than experiment (different rho? different chicane position? Starting energy spread? Different taper?)
Thanks toZ. Huang, J. Wu, J. Welch, Y. DingJ.Krzywinski, Y. Feng, Y. Shvyd’koS. Spampinati