Seeded jitter studies
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Seeded jitter studies. Z. Huang, et al., November 7, 2012. Seeding MD (May 15). 150 pC , SASE vs. Seeded after Kmono E-beam energy 13.64 GeV , photon energy 8.3 keV Bragg angle 57.875 deg for 004 seeding (accurate to 0.001 deg) Kmono bandwidth ~1 eV

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Seeded jitter studies

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Seeded jitter studies

Seeded jitter studies

Z. Huang, et al.,

November 7, 2012


Seeded jitter studies

Seeding MD (May 15)

  • 150 pC, SASE vs. Seeded after Kmono

  • E-beam energy 13.64 GeV, photon energy 8.3 keV

  • Bragg angle 57.875 deg for 004 seeding (accurate to 0.001 deg)

  • Kmono bandwidth ~1 eV

  • Tune on Kmono diode signal not on gas detector

     BC2 Ipk=2 kA, L1S=-24.5 deg, L1X=-160 deg, U1-2 out

  • Gas detector shows 0.5 mJ SASE, and seeded peaks at 1 mJ


Seeded jitter studies

Seeded jitter sensitivity studies with Kmono

Seeded intensity vs. linac energy

(rms energy jitter 5e-4)

average 6.8 (rms intensity jitter 72%)

average 11.5 (rms intensity jitter 22%)

Filter out energy jitter


Seeded jitter studies

Seeded jitter sensitivity studies with Kmono

Seeded intensity vs. linac energy

(rms energy jitter 5e-4)

average 6.8 (rms intensity jitter 72%)

average 10.9 (rms intensity jitter 25%)

Reduce energy jitter to 1.8e-4


Seeded jitter studies

1D FEL Simulation

FEL parameter ρ= 5 x 10 -4

A. Lutman

Electron beam at undulator entrance

Flat current and electron energy profile

Random electron beam central energy with Gaussian Distribution

energy

Uncorrelated energy spread with

average = 0.6 ρ

rms= 0.1 ρ

Uncorrelated

energy spread

central energy

Seed Laser

Flat seed laser profile

phase

Intensity distributed as negative exponential with average 5 MW


Seeded jitter studies

Electron Beam energy vsIntensity (7 x 10-4relative energy rms)

Total Intensity

2 gl after saturation

2 gl before saturation

4 gl after saturation

Intensity in 1 eV

2 gl after saturation

2 gl before saturation

4 gl after saturation


Seeded jitter studies

Amplification Bandwidth and Fluctuations, comparison with experimental data

Experimental Data

Kmono measurement

05/15/2012

Simulated Data

2 gain lengths after saturation

Without taper

Relative energy rms 7 x 10-4

Relative energy rms7.2 x 10-4

Fluctuations (1eV) 70%

Fluctuations 72%

Relative amplification bandwidth (fit rms) 3.5 x 10-4

(relative energy)

Relative amplification bandwidth (fit rms) 3.5 x 10-4

(relative energy)


Seeded jitter studies

(111) Seeding at 5.5 keV

(004)

J. Hastings

(111)

2.0

35.26

(220)

Diamond

seed beam

With input beam perpendicular to the

Crystal the photon energy for the (111) is

5.21 keV


Seeded jitter studies

Undulator taper at 5.5 keV

Taper response

Maximum FEL intensity (>400 uJ) responses well to strong undulator taper

40 pCbunch length < 10 fs, maximum peak power > 40 GW


Seeded jitter studies

Comparison of taper result

on-energy shots

J. Wu

experiment

simulation

off-energy shots

Simulation for energy jitter: blue (on-energy), black (+0.1 %), red ( -0.1 % ), magenta (-0.2 %)


Summary

Summary

  • Seeded FEL power is very sensitive to linacenergyjitters.

  • Need to improve energy jitters to < 2e-4 (rms).

  • Seeded FEL responses to energy jitter and undulator taper appear to agree with simulations, but the relevant data set is small.


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