IPAC2017 - List of Authors (Ferrari, E.)

Paper	Title	Page
WEZA2	Polarization Control in High Gain Free Electron Lasers
	E. Ferrari Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Funding: Italian-Slovenian Crossborder Programme, Slovenian Research Agency, Volkswagen Foundation, LOEWE-Focus ELCH, Triangle de la Physique, Italian Ministry of University and Research. Methods for the control of polarization of the radiation emitted in high gain free electron lasers (FELs) are recalled. The first demonstration of full polarization control in the extreme ultra-violet at FERMI FEL is presented, and the polarization characterized by three independent instruments and methods. The measured radiation polarization is consistently > 90%; observed effects of photon beam transport from the undulator to the radiation detectors is discussed. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.* * E. Allaria et al., PRX 4, 041040 (2014)
	Slides WEZA2 [41.915 MB]
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THYA1	New Scenarios of Microbunching Instability Control in Electron Linacs and Free Electron Lasers	3642
	E. Roussel, E. Allaria, M.B. Danailov, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. We demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL. *E. Roussel et al., Phys. Rev. Lett. 115, 214801 (2015)
	Slides THYA1 [14.837 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THYA1
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WEPAB034	Control of Seeded FEL Pulse Duration Using Laser Heater Pulse Shaping	2654
	V. Grattoni Università degli Studi di Trieste, Trieste, Italy E. Allaria, L. Badano, M.B. Danailov, A.A. Demidovich, S. Di Mitri, L. Giannessi, G. Penco, E. Roussel, P. Sigalotti, S. Spampinati, M. Trovò, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy E. Ferrari PSI, Villigen PSI, Switzerland
	New Free-Electron Laser facilities deliver VUV and X-ray radiation with pulse length in the range of hundreds and tens of fs. A further reduction of the FEL pulse length is desired by those experiments aiming at probing ultrafast phenomena. Unlike SASE FEL, where the pulse duration is mainly driven by the electron bunch duration, in a seeded FEL the pulse duration can be determined by the seed laser properties. The use of techniques able to locally deteriorate the electron beam properties such as emittance or energy spread have been used in SASE FELs to reduce the region of the electron beam that is able to produce FEL radiation and hence reduce the FEL pulse length. The temporal shaping of the laser heater can be used to create an electron beam characterized by a very large energy spread all along the bunch except for a small region. We report measurements of the effect of the laser heater shaping on the electron beam phase-space performed at FERMI. Impact on the final FEL pulse properties are predicted with a series of numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB034
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WEPVA020	Dual-Grating Dielectric Accelerators Driven by A Pulse-Front-Tilted Laser	3299
	Y. Wei, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom M.M. Dehler, E. Ferrari, N. Hiller, R. Ischebeck PSI, Villigen PSI, Switzerland J.D.A. Smith TXUK, Warrington, United Kingdom C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom G.X. Xia UMAN, Manchester, United Kingdom
	Dual-grating Dielectric Laser-driven Accelerators (DLAs) are considered to be one of the most promising technologies to miniaturize future particle accelerators. Accelerating gradients in the GV/m range seem accessible and 690 MV/m has been demonstrated in fused silica structures. However, the increase in beam energy is limited by the short interaction length between the laser pulses and the electron bunch. In this contribution, a pulse-front-tilt operation for a laser beam is studied to extend the interaction length, resulting in a greater energy gain for a dual-grating DLA. The VSIM code is used to compare this new scheme with the commonly used approach of a normally incident laser beam and advantages are summarized. [1]T. Plettner, et al., Phys. Rev. ST Accel. Beams 9, 111301 (2006) [2]K. P. Wootton, et al., Opt. Lett., 41, 2696 (2016). [3]E. A. Peralta, et al., Nature 503, 91 (2013)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA020
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Paper

Title

Page

WEZA2

Polarization Control in High Gain Free Electron Lasers

E. Ferrari
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Funding: Italian-Slovenian Crossborder Programme, Slovenian Research Agency, Volkswagen Foundation, LOEWE-Focus ELCH, Triangle de la Physique, Italian Ministry of University and Research.
Methods for the control of polarization of the radiation emitted in high gain free electron lasers (FELs) are recalled. The first demonstration of full polarization control in the extreme ultra-violet at FERMI FEL is presented, and the polarization characterized by three independent instruments and methods. The measured radiation polarization is consistently > 90%; observed effects of photon beam transport from the undulator to the radiation detectors is discussed. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.*
* E. Allaria et al., PRX 4, 041040 (2014)

Slides WEZA2 [41.915 MB]

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYA1

New Scenarios of Microbunching Instability Control in Electron Linacs and Free Electron Lasers

3642

E. Roussel, E. Allaria, M.B. Danailov, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. We demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL.
*E. Roussel et al., Phys. Rev. Lett. 115, 214801 (2015)

Slides THYA1 [14.837 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THYA1

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WEPAB034

Control of Seeded FEL Pulse Duration Using Laser Heater Pulse Shaping

2654

V. Grattoni
Università degli Studi di Trieste, Trieste, Italy
E. Allaria, L. Badano, M.B. Danailov, A.A. Demidovich, S. Di Mitri, L. Giannessi, G. Penco, E. Roussel, P. Sigalotti, S. Spampinati, M. Trovò, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
E. Ferrari
PSI, Villigen PSI, Switzerland

New Free-Electron Laser facilities deliver VUV and X-ray radiation with pulse length in the range of hundreds and tens of fs. A further reduction of the FEL pulse length is desired by those experiments aiming at probing ultrafast phenomena. Unlike SASE FEL, where the pulse duration is mainly driven by the electron bunch duration, in a seeded FEL the pulse duration can be determined by the seed laser properties. The use of techniques able to locally deteriorate the electron beam properties such as emittance or energy spread have been used in SASE FELs to reduce the region of the electron beam that is able to produce FEL radiation and hence reduce the FEL pulse length. The temporal shaping of the laser heater can be used to create an electron beam characterized by a very large energy spread all along the bunch except for a small region. We report measurements of the effect of the laser heater shaping on the electron beam phase-space performed at FERMI. Impact on the final FEL pulse properties are predicted with a series of numerical simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB034

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WEPVA020

Dual-Grating Dielectric Accelerators Driven by A Pulse-Front-Tilted Laser

3299

Y. Wei, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
M.M. Dehler, E. Ferrari, N. Hiller, R. Ischebeck
PSI, Villigen PSI, Switzerland
J.D.A. Smith
TXUK, Warrington, United Kingdom
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
G.X. Xia
UMAN, Manchester, United Kingdom

Dual-grating Dielectric Laser-driven Accelerators (DLAs) are considered to be one of the most promising technologies to miniaturize future particle accelerators. Accelerating gradients in the GV/m range seem accessible and 690 MV/m has been demonstrated in fused silica structures. However, the increase in beam energy is limited by the short interaction length between the laser pulses and the electron bunch. In this contribution, a pulse-front-tilt operation for a laser beam is studied to extend the interaction length, resulting in a greater energy gain for a dual-grating DLA. The VSIM code is used to compare this new scheme with the commonly used approach of a normally incident laser beam and advantages are summarized.
[1]T. Plettner, et al., Phys. Rev. ST Accel. Beams 9, 111301 (2006)
[2]K. P. Wootton, et al., Opt. Lett., 41, 2696 (2016).
[3]E. A. Peralta, et al., Nature 503, 91 (2013)

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA020

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