The echo-enabled harmonic generation (EEHG) options for

FLASH IIHaixiao Deng, Winfried Decking, Bart FaatzHaixiao Deng, Winfried Decking, Bart Faatz

FEL division, Shanghai Institute of Applied Physics (SINAP)FEL division, Shanghai Institute of Applied Physics (SINAP)Hasylab, Deutsches Elektronen-Synchrotron (DESY)Hasylab, Deutsches Elektronen-Synchrotron (DESY)

DESY, Hamburg, Dec 06, 2010DESY, Hamburg, Dec 06, 2010

denghaixiao@sinap.ac.cndenghaixiao@sinap.ac.cn

Free Electron Laser Beam Dynamics Meeting

Contents

Introduction

EEHG options for FLASH II

Numerical modeling

Beam energy chirp & CSR effects

FEL properties & Discussions

Summary & Outlook

Acknowledgments

Introduction

Echo-enabled

harmonic generation

(EEHG)

Why EEHG ?

G. Stupakov, EEHG for seeded FEL-theory and experiment, KEK, Nov, 2010

Current status of EEHG

Works in the theoretical frame G. Stupakov., PRL, 102, 074801 (2009) D. Xiang et al., PR-ST AB, 12, 030702 (2009) D. Xiang et al., PR-ST AB, 12, 080701 (2009) Z. Huang et al., FEL09, MOPC45 D. Xiang et al., PR-ST AB, 12, 060701 (2009) G. Pen et al., NIMA, 612, 254 (2010) J. Yan et al., NIMA, 621, 97 (2010)

Experimental demonstration of the EEHG signal at SDUV-FEL & NLCTA, independently.

Z. T. Zhao et al., IPAC10, FEL10 D. Xiang et al., PRL, 105, 114801 (2010)

FERMI, Swiss-FEL, FLASH II, LCLS II/III etc.

EEHG options for FLASH II

EEHG options for FLASH II

EEHG optimization for FLASH II

EEHG theory EEHG simulation: steady-state

Main parameters

The ideal projected bunching

20th harmonic 60th harmonic 40th harmonic

Numerical modeling

Macro-particles generator(GENESIS & ASTRA )

3D laser-beam interaction in Modulator1(MATLAB program)

3D laser-beam interaction in Modulator2 & Chicane 2 *(MATLAB program)

Particle tracking in Chicane1(ELEGANT & CSRtrack)

Self-consistent FEL simulation in the main radiator(GENESIS)

* The dynamics of Chicane 2 (small R56) is just linear optics

Numerical modeling

All procedures are controlled by MATLAB scripts

Laser-beam interaction algorithm

Detuning of LCLS laser-heater CEP effects of a fs laser

• No FEL equation induced, capable for fs seed laser• Beam dynamics under field maps (Electric & magnetic)• Radiations from the electron beam are ignored

Haixiao Deng et al, Chinese Physics C, 2011, in press

Self-consistent FEL simulation• The problem in the conventional s2e simulation• Self-consistent s2e FEL simulation *• SASE start-up, fluctuation and noise propagation• 1pC, single-spike mode for SXFEL, 6M macro-particles

* Jun Yan, Meng Zhang and Haixiao Deng, NIMA 615, 249 (2010)

Beam energy chirp & CSR effects

Flash 1nC s2e results

Z. Huang et al., FEL09, MOPC45

Energy chirp effects

20th harmonic 60th harmonic 40th harmonic

The CSR-induced emittance growth

60th harmonic EEHG for FLASH II, 2.5kA peak current case

10% growth of the projected emittance

CSR effects on EEHG microbunching

Without CSR 2.5kA, with CSR 1.25kA, with CSR

20th harmonic EEHG for FLASH II

CSR effects on EEHG microbunching

Without CSR 2.5kA, with CSR 1.25kA, with CSR

40th harmonic EEHG for FLASH II

CSR effects on EEHG microbunching

Without CSR 2.5kA, with CSR 1.25kA, with CSR

60th harmonic EEHG for FLASH II

How CSR induces degradation ?

Firstly, the electron beam radiates significant CSR filed in the chicane.

Secondly, CSR-beam interaction introduces the energy modulation. Since the longitudinal variation of the CSR field, it results different energy chirp in different part of the beam.

Thirdly, different parts of the electron beam shift to different microbunching wavelength.

Thus, the projected microbunching bandwidth is broadened and the bunching factor is degraded.

FEL performances & Discussions

20th harmonic 60th harmonic 40th harmonic

Blue: 1.25kA peak current caseRed: 2.50kA peak current case

Initial sliced bunching factor at the radiator entrance

Peak power & pulse energy

Radiation power & radiation phase

D1. benchmark with CSRtrack

Elegant results CSRtrack results

Hereafter, several interested issues are stressed, we use the 20th harmonic EEHG option of FLASH II, 2.5kA peak current case in the following discussions.

D1. benchmark with CSRtrack

Elegant results CSRtrack results

With the presence of the ‘projected’ type CSR force, the bandwidth of the projected bunching factor is broadened and the amplitude of the projected bunching factor degraded. It is reasonably agree with the ELEGANT results. Meanwhile, some differences are observed, which may be attributed by the numerical errors.

D2. sensitivity on the 2nd chicane

Microbunching wavelength .vs. R56(2)

With chirp & without CSR effects

Microbunching factor .vs. R56(2)Without chirp & with CSR effects

A stability of 1% of the R56 in the 2nd chicane is required.

D3. dependence on macro-particles

Peak power growth Pulse energy growth

Initial sliced bunching

D3. dependence on macro-particles

Saturated radiation pulse

D4. longitudinal coherence

TBP=0.5, close to FTL TBP=1,close to FTL

D4. longitudinal coherence

6 times larger bandwidth than FTL TBP=1,close to FTL

D5. EEHG fine structures

The EEHG story was preserved at each local region of the electron beam

D6. MBI in the large chicane

Z. Huang et al., SLAC-PUB 9538 (2002).

D7. issues on the seed laser noise

1% RMS amplitude noise and 1 degree RMS phase noise are introduced

D7. issues on the seed laser noise

Only 1% RMS amplitude noise of 262nm seed laser, no shot noise, no CSR

D7. issues on the seed laser noise

Electron beam shot noise is not included, we use 200 slices flat-top beam

Summary & Outlook

Robust numerical model for EEHG is developed by combining the existing well-benchmarked code. It is capable for linear energy chirp, CSR and the seed laser noise simulation.

Energy chirp induces beam modulation frequency shift.

CSR degrades the projected bunching a lot, but it has a limited effects on the sliced bunching, especially when the seed laser is under 100fs, or even shorter.

EEHG options for FLASH II was studied for the first time. From the simulation, at even 60th high harmonic case, the strong coherent harmonic generation and longitudinal coherence can be preserved in EEHG. However, we should start from the 20th harmonic EEHG case.

Summary & Outlook

Future suggestions on EEHG simulation How to preserve the noise level of a Gaussian

bunch ? Do we need a new CSR model for EEHG modulated

micro-structures ? As the energy modulation induced by a laser-

heater, can the beam shot noise damp the seed laser noise effects to some extent ?

Start2end simulation. i.e., including bunch compressor of FLASH LINAC and the extraction arc of FLASH II.

The pulse edge of the 262nm seed laser would attribute the bandwidth broadening in EEHG.

More tolerance studies, time jitter effects. Alternative Chicane parameters. CSR effects in Chicane 2, etc.

Acknowledgments

Jianhui Chen, Meng Zhang, Bo Liu, Qiang Gu, Dong Wang and Zhimin Dai from SINAP, Matthias Scholz, Igor Zagorodnov, Torsten Limberg and Martin Dohlus from DESY, Yuhui Li from European XFEL, Yuantao Ding, Juhao

Wu and Zhirong Huang from SLAC, Jun Yan from DUKE University.

Special thanks to Dong Wang, WinfriedWinfried Decking and Bart Faatz for organization and operation of such a collaboration.

Thanks for your attentions