Fluctuations Study Update
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Transcript of Fluctuations Study Update
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