FEL2019 - List of Authors (Yang, X.)

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MOD04

Post-Saturation Dynamics and Superluminal Propagation of a Super-Radiant Spike in a Free-Electrons Laser Amplifier

X. Yang
BNL, Upton, New York, USA
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
L. Giannessi, N.S. Mirian
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The generation of a single X-ray isolated spike of radiation with peak power at multi-GW level and femtosecond temporal duration represents a unique opportunity in time resolved diffraction imaging of isolated molecules or non-periodic structures for acquiring single shot images before the Coulomb explosion of the sample takes place. Such a condition is met by an FEL operating in superradiant regime for the possibility of simultaneously reducing the pulse duration while increasing the peak power and the pulse energy. We study the dynamics of an isolated spike of radiation in superradiant regime. We show that conditions exist where the pulse moves with a group velocity larger than one and is followed by a pedestal resulting from a complex post-saturation dynamic. The tail is constituted by a train of sub-pulses with both transverse and longitudinal coherence and decaying amplitudes. We analyze the dynamical conditions leading to the formation of the main pulse and the tail. We study the correlation of the tail structure with the longitudinal phase space of the electrons and provide a recipe to partially suppress this tail.

Slides MOD04 [7.203 MB]

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TUB04

Generation and Measurement of Intense Few-Femtosecond Superradiant Soft X-Ray Free Electron Laser Pulses

S. Spampinati, E. Allaria, L. Badano, C. Callegari, G. De Ninno, M. Di Fraia, S. Di Mitri, L. Giannessi, N. Mahne, M. Manfredda, N.S. Mirian, G. Penco, O. Plekan, K.C. Prince, L. Raimondi, P. Rebernik Ribič, C. Spezzani, M. Trovò, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
R. Feifel, R. Squibb
Uppsala University, Uppsala, Sweden
T. Mazza
EuXFEL, Hamburg, Germany
X. Yang
BNL, Upton, New York, USA

Intense FEL VUV and soft X-ray pulses with a time duration of few fs allows to probe ultrafast, out-of equilibrium dynamics or to pump the sample driving new phase transitions in regimes where uniform heating is not depleted by secondary energy decay channels, such as Auger effect [Principi]. Most of the methods proposed to reduce the FEL pulse duration are based on a manipulation of longitudinal electron beam properties such as emittance, beam current, energy spread, trajectory or optical functions. We present an attractive alternative based on the exploitation of the FEL dynamic process itself, driving the FEL amplifier in saturation and superradiance in a cascade of undulators resonant at higher harmonics of an initial seed. At FERMI we have implemented for the first time a multistage superradiant cascade reaching EUV-soft X-ray wavelengths and producing high-power, stable, FEL pulses with a duration of about 5 fs. We report here the analysis of the configuration used and of the characterization of the radiation produced in this regime.

Slides TUB04 [3.300 MB]

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Paper	Title	Page
MOD04	Post-Saturation Dynamics and Superluminal Propagation of a Super-Radiant Spike in a Free-Electrons Laser Amplifier
	X. Yang BNL, Upton, New York, USA L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy L. Giannessi, N.S. Mirian Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	The generation of a single X-ray isolated spike of radiation with peak power at multi-GW level and femtosecond temporal duration represents a unique opportunity in time resolved diffraction imaging of isolated molecules or non-periodic structures for acquiring single shot images before the Coulomb explosion of the sample takes place. Such a condition is met by an FEL operating in superradiant regime for the possibility of simultaneously reducing the pulse duration while increasing the peak power and the pulse energy. We study the dynamics of an isolated spike of radiation in superradiant regime. We show that conditions exist where the pulse moves with a group velocity larger than one and is followed by a pedestal resulting from a complex post-saturation dynamic. The tail is constituted by a train of sub-pulses with both transverse and longitudinal coherence and decaying amplitudes. We analyze the dynamical conditions leading to the formation of the main pulse and the tail. We study the correlation of the tail structure with the longitudinal phase space of the electrons and provide a recipe to partially suppress this tail.
	Slides MOD04 [7.203 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUB04	Generation and Measurement of Intense Few-Femtosecond Superradiant Soft X-Ray Free Electron Laser Pulses
	S. Spampinati, E. Allaria, L. Badano, C. Callegari, G. De Ninno, M. Di Fraia, S. Di Mitri, L. Giannessi, N. Mahne, M. Manfredda, N.S. Mirian, G. Penco, O. Plekan, K.C. Prince, L. Raimondi, P. Rebernik Ribič, C. Spezzani, M. Trovò, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy R. Feifel, R. Squibb Uppsala University, Uppsala, Sweden T. Mazza EuXFEL, Hamburg, Germany X. Yang BNL, Upton, New York, USA
	Intense FEL VUV and soft X-ray pulses with a time duration of few fs allows to probe ultrafast, out-of equilibrium dynamics or to pump the sample driving new phase transitions in regimes where uniform heating is not depleted by secondary energy decay channels, such as Auger effect [Principi]. Most of the methods proposed to reduce the FEL pulse duration are based on a manipulation of longitudinal electron beam properties such as emittance, beam current, energy spread, trajectory or optical functions. We present an attractive alternative based on the exploitation of the FEL dynamic process itself, driving the FEL amplifier in saturation and superradiance in a cascade of undulators resonant at higher harmonics of an initial seed. At FERMI we have implemented for the first time a multistage superradiant cascade reaching EUV-soft X-ray wavelengths and producing high-power, stable, FEL pulses with a duration of about 5 fs. We report here the analysis of the configuration used and of the characterization of the radiation produced in this regime.
	Slides TUB04 [3.300 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)