IPAC2021 - List of Keywords (free-electron-laser)

Paper	Title	Other Keywords	Page
MOPAB099	Intensity Fluctuations Reduction in the Double-Bunch FEL at LCLS	FEL, electron, laser, undulator	369
	G. Zhou, A. Halavanau, C. Pellegrini SLAC, Menlo Park, California, USA
	In this paper we explore the possibility of reducing the intensity fluctuations of a hard X-ray double-bunch free-electron laser (DBFEL) by using an ultra-short, high peak current electron bunch to generate the seed signal, as studied recently for soft X-ray single bunch self-seeding. The ultra-short, nearly single-spike, SASE pulse is amplified to saturation, where a four-crystal monochromator selects a narrow bandwidth seed for the second bunch. Start-to-end simulation results for 7 keV photon energy are presented here for a DBFEL already studied for LCLS using the HXR undulator. We show that using this enhanced DBFEL (EDBFEL) system; the seed signal intensity fluctuations can be reduced from 85% to about 30%, and the second bunch intensity fluctuation at saturation to about 15%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB099
About •	paper received ※ 24 May 2021 paper accepted ※ 16 July 2021 issue date ※ 31 August 2021
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MOPAB150	Optimization of the Gain Medium Delivery System for an X-Ray Laser Oscillator	laser, electron, target, FEL	524
	M. Yadav, N. Majernik, P. Manwani, B. Naranjo, C. Pellegrini, J.B. Rosenzweig UCLA, Los Angeles, California, USA E.C. Galtier, A. Halavanau, C. Pellegrini SLAC, Menlo Park, California, USA A. Malinouski ASC HMTI, Minsk, Belarus
	Funding: This work was supported by DE-SC0009914. X-ray laser oscillator, dubbed XLO, is a recently proposed project at SLAC to build the first population inversion X-ray laser. XLO utilizes a train of XFEL SASE pulses to pump atomic core-states. The resulting amplified spontaneous emission radiation is recirculated in a backscattering Bragg cavity and subsequently amplified. XLO could provide fully coherent, transform-limited X-ray pulses with 50 meV bandwidth and 1e10 photons. Currently, XLO is being considered for operation at the copper K-alpha line at 8048 eV. In this work, we focus on the optimization of gain medium delivery in the XLO cavity. We consider a fast, subsonic jet of copper nitrate solution, moving through a cylindrical nozzle. We focus on the nozzle geometry optimization and possible diagnostics of the jet-XFEL interaction point.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB150
About •	paper received ※ 24 May 2021 paper accepted ※ 18 June 2021 issue date ※ 27 August 2021
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TUPAB072	The Status of a Grating Monochromator for Soft X-Ray Self-Seeding Experiment at SHINE	electron, laser, FEL, cavity	1532
	K.Q. Zhang SSRF, Shanghai, People’s Republic of China H.X. Deng, C. Feng, B. Liu, T. Liu SARI-CAS, Pudong, Shanghai, People’s Republic of China
	The research status of a grating monochromator for soft X-ray self-seeding experiment at SHINE has been presented in this paper. The monochromator system includes the vacuum cavity, optical elements, and mechanical movement devices. Until now, the vacuum cavity has finished the manufactured process completely, the optical mirrors have finished machining and measured by the longitudinal trace profiler (LTP) and atomic force microscope (AFM). To make sure the monochromator system can achieve an optical resolution of 1/10000 at the photon energy of 700-1300eV, the system has been integrated and tested recently. In this year, the previous online experiment will be performed in the shanghai soft X-ray free-electron laser (FEL) user facility.
	Poster TUPAB072 [0.717 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB072
About •	paper received ※ 11 May 2021 paper accepted ※ 09 June 2021 issue date ※ 01 September 2021
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TUPAB084	An Empirically-Derived ABCD Matrix for Transverse Dynamics Studies in Seeded Free-Electron Lasers	FEL, radiation, electron, laser	1573
	R. Robles Stanford University, Stanford, California, USA Z. Huang, G. Marcus SLAC, Menlo Park, California, USA
	Funding: DOE Contract DE-AC02-76SF00515. We present a simple empirical method for deriving an ABCD matrix for studying the transverse dynamics of the radiation field in seeded, high-gain free-electron lasers before saturation. In spite of the inherently nonlinear nature of FEL optical guiding, the ABCD matrix we find is able to predict the evolution of the FEL mode size and centroid to a high degree of accuracy across a large range of input mode characteristics. This scheme enables extremely fast simulation of transverse dynamics, which in turn greatly simplifies numerical studies of seeded FEL systems. Of particular interest in that regard is the x-ray regenerative amplifier free-electron laser, in which the x-ray beam propagates through an optical cavity many hundreds of times, thereby making traditional simulation methods cumbersome and time consuming.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB084
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 11 August 2021
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TUPAB111	Layout of the Laser Heater for FLASH2020+	electron, laser, undulator, FEL	1647
	C. Gerth, E. Allaria, A. Choudhuri, L. Schaper, E. Schneidmiller, S. Schreiber, M. Tischer, P. Vagin, M. Vogt, L. Winkelmann, M.V. Yurkov, J. Zemella DESY, Hamburg, Germany
	The major upgrade FLASH2020+ of the FEL user facility FLASH includes an improved injector layout for the generation of the high-brightness electron beam as well as an externally seeded FEL beamline. Microbunching gain of initial modulations or shot-noise fluctuations degrade the electron beam quality, which is in particular harmful to the external seed process. To minimize the microbunching gain by a controlled increase of the uncorrelated energy spread, the installation of a laser heater is foreseen directly upstream of the first bunch compression chicane. In this paper, we present the layout of the laser heater section, which follows the original proposal published almost 20 years ago and differs in several aspects from the common layout implemented at many other FEL facilities. The considerations that have been made for the optimisation of the laser heater parameters are described in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB111
About •	paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 01 September 2021
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TUPAB126	Spectral Gap in the Middle Infrared FEL Oscillator of FELiCHEM	FEL, GUI, laser, electron	1685
	Y.P. Zhu, H.T. Li, Z. Zhao USTC/NSRL, Hefei, Anhui, People’s Republic of China
	A phenomenon of spectral gap is observed in the Middle Infrared FEL Oscillator of FELiCHEM: the laser power falls down at the particular wavelength. Starting with the experimental data, this paper focuses on the simulation calculation and analysis of the effect from using the partial waveguide. The relationship between waveguide and spectral gap is revealed.
	Poster TUPAB126 [1.063 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB126
About •	paper received ※ 17 May 2021 paper accepted ※ 14 June 2021 issue date ※ 21 August 2021
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WEPAB228	Modelling and Counteracting Microbunching Instability in Spreader Lines of Radiofrequency and Plasma-Based Accelerators for Free-Electron Lasers	electron, bunching, laser, scattering	3165
	G. Perosa Università degli Studi di Trieste, Trieste, Italy S. Di Mitri Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	High energy radiofrequency and plasma-driven accelerators target electron beam brightness suitable for x-ray free-electron lasers. Microbunching instability can be enhanced during beam transport through the spreader line from the accelerator to the undulator, degrading the brightness of the accelerated beam and therefore reducing the lasing efficiency. We present a semi-analytical model of the instability, benchmarked with experimental data at the FERMI free-electron laser, in the presence of intrabeam scattering and beam heating. Strategies for minimization of the instability both in conventional and plasma-based accelerators are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB228
About •	paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 02 September 2021
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THPAB313	Drive Laser System for Shanghai Soft X-Ray Free Electron Laser	laser, FEL, electron, cathode	4403
	L. Feng, C.L. Li, B. Liu, J.G. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China X. Lu ANL, Lemont, Illinois, USA X.T. Wang, W.Y. Zhang Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
	In this paper, we introduce the design and layout of the drive laser of Shanghai Soft X-ray Free Electron Laser (SXFEL). It is known that the temporal and spatial distribution of the drive laser is crucial for high-quality electron beams. The drive laser provides the laser pulse of 266nm wavelength and 8ps pulse duration for the photocathode, as well as 400nm wavelength, 2-20ps tunable pulse duration for the laser heater. For this purpose, there are mainly four parts in such system, including a third-harmonic generation device, pulse stretcher, image transmitted system, and laser optical module for laser heater. Finally, the measured results of the electron beam under this drive laser system are presented and discussed.
	Poster THPAB313 [0.691 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB313
About •	paper received ※ 20 May 2021 paper accepted ※ 15 July 2021 issue date ※ 24 August 2021
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FRXA06	Mitigation of Beam Instabilities in the Echo-Enabled Harmonic Generation Beamline for FLASH2020+	bunching, laser, electron, FEL	4514
	F. Pannek, W. Hillert, D. Samoilenko University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Ackermann, E. Allaria, P. Niknejadi, G. Paraskaki, L. Schaper DESY, Hamburg, Germany M.A. Pop MAX IV Laboratory, Lund University, Lund, Sweden
	With the FLASH2020+ upgrade, one of the beamlines of the free-electron laser FLASH at DESY will be based on the Echo-Enabled Harmonic Generation (EEHG) seeding scheme and provide high-repetition-rate, coherent radiation down to 4 nm. To reach this wavelength, it is necessary to imprint intricate structures on the longitudinal phase space of the electron bunch at a very high harmonic of the seed laser wavelength, making the scheme potentially vulnerable to beam instabilities. Part of the beamline is a strong chicane, which is necessary to create the dispersion required by EEHG. Resulting effects such as Coherent Synchrotron Radiation (CSR) can be very detrimental for the bunching process and have to be taken into account already in the design of the beamline to ensure optimum FEL performance. We investigate and propose possible mitigation solutions to such instabilities in the FLASH2020+ parameter range.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA06
About •	paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 20 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPAB099

Intensity Fluctuations Reduction in the Double-Bunch FEL at LCLS

FEL, electron, laser, undulator

369

G. Zhou, A. Halavanau, C. Pellegrini
SLAC, Menlo Park, California, USA

In this paper we explore the possibility of reducing the intensity fluctuations of a hard X-ray double-bunch free-electron laser (DBFEL) by using an ultra-short, high peak current electron bunch to generate the seed signal, as studied recently for soft X-ray single bunch self-seeding. The ultra-short, nearly single-spike, SASE pulse is amplified to saturation, where a four-crystal monochromator selects a narrow bandwidth seed for the second bunch. Start-to-end simulation results for 7 keV photon energy are presented here for a DBFEL already studied for LCLS using the HXR undulator. We show that using this enhanced DBFEL (EDBFEL) system; the seed signal intensity fluctuations can be reduced from 85% to about 30%, and the second bunch intensity fluctuation at saturation to about 15%.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB099

About •

paper received ※ 24 May 2021 paper accepted ※ 16 July 2021 issue date ※ 31 August 2021

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

MOPAB150

Optimization of the Gain Medium Delivery System for an X-Ray Laser Oscillator

laser, electron, target, FEL

524

M. Yadav, N. Majernik, P. Manwani, B. Naranjo, C. Pellegrini, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
E.C. Galtier, A. Halavanau, C. Pellegrini
SLAC, Menlo Park, California, USA
A. Malinouski
ASC HMTI, Minsk, Belarus

Funding: This work was supported by DE-SC0009914.
X-ray laser oscillator, dubbed XLO, is a recently proposed project at SLAC to build the first population inversion X-ray laser. XLO utilizes a train of XFEL SASE pulses to pump atomic core-states. The resulting amplified spontaneous emission radiation is recirculated in a backscattering Bragg cavity and subsequently amplified. XLO could provide fully coherent, transform-limited X-ray pulses with 50 meV bandwidth and 1e10 photons. Currently, XLO is being considered for operation at the copper K-alpha line at 8048 eV. In this work, we focus on the optimization of gain medium delivery in the XLO cavity. We consider a fast, subsonic jet of copper nitrate solution, moving through a cylindrical nozzle. We focus on the nozzle geometry optimization and possible diagnostics of the jet-XFEL interaction point.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB150

About •

paper received ※ 24 May 2021 paper accepted ※ 18 June 2021 issue date ※ 27 August 2021

Export •

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

TUPAB072

The Status of a Grating Monochromator for Soft X-Ray Self-Seeding Experiment at SHINE

electron, laser, FEL, cavity

1532

K.Q. Zhang
SSRF, Shanghai, People’s Republic of China
H.X. Deng, C. Feng, B. Liu, T. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China

The research status of a grating monochromator for soft X-ray self-seeding experiment at SHINE has been presented in this paper. The monochromator system includes the vacuum cavity, optical elements, and mechanical movement devices. Until now, the vacuum cavity has finished the manufactured process completely, the optical mirrors have finished machining and measured by the longitudinal trace profiler (LTP) and atomic force microscope (AFM). To make sure the monochromator system can achieve an optical resolution of 1/10000 at the photon energy of 700-1300eV, the system has been integrated and tested recently. In this year, the previous online experiment will be performed in the shanghai soft X-ray free-electron laser (FEL) user facility.

Poster TUPAB072 [0.717 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB072

About •

paper received ※ 11 May 2021 paper accepted ※ 09 June 2021 issue date ※ 01 September 2021

Export •

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

TUPAB084

An Empirically-Derived ABCD Matrix for Transverse Dynamics Studies in Seeded Free-Electron Lasers

FEL, radiation, electron, laser

1573

R. Robles
Stanford University, Stanford, California, USA
Z. Huang, G. Marcus
SLAC, Menlo Park, California, USA

Funding: DOE Contract DE-AC02-76SF00515.
We present a simple empirical method for deriving an ABCD matrix for studying the transverse dynamics of the radiation field in seeded, high-gain free-electron lasers before saturation. In spite of the inherently nonlinear nature of FEL optical guiding, the ABCD matrix we find is able to predict the evolution of the FEL mode size and centroid to a high degree of accuracy across a large range of input mode characteristics. This scheme enables extremely fast simulation of transverse dynamics, which in turn greatly simplifies numerical studies of seeded FEL systems. Of particular interest in that regard is the x-ray regenerative amplifier free-electron laser, in which the x-ray beam propagates through an optical cavity many hundreds of times, thereby making traditional simulation methods cumbersome and time consuming.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB084

About •

paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 11 August 2021

Export •

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

TUPAB111

Layout of the Laser Heater for FLASH2020+

electron, laser, undulator, FEL

1647

C. Gerth, E. Allaria, A. Choudhuri, L. Schaper, E. Schneidmiller, S. Schreiber, M. Tischer, P. Vagin, M. Vogt, L. Winkelmann, M.V. Yurkov, J. Zemella
DESY, Hamburg, Germany

The major upgrade FLASH2020+ of the FEL user facility FLASH includes an improved injector layout for the generation of the high-brightness electron beam as well as an externally seeded FEL beamline. Microbunching gain of initial modulations or shot-noise fluctuations degrade the electron beam quality, which is in particular harmful to the external seed process. To minimize the microbunching gain by a controlled increase of the uncorrelated energy spread, the installation of a laser heater is foreseen directly upstream of the first bunch compression chicane. In this paper, we present the layout of the laser heater section, which follows the original proposal published almost 20 years ago and differs in several aspects from the common layout implemented at many other FEL facilities. The considerations that have been made for the optimisation of the laser heater parameters are described in detail.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB111

About •

paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 01 September 2021

Export •

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

TUPAB126

Spectral Gap in the Middle Infrared FEL Oscillator of FELiCHEM

FEL, GUI, laser, electron

1685

Y.P. Zhu, H.T. Li, Z. Zhao
USTC/NSRL, Hefei, Anhui, People’s Republic of China

A phenomenon of spectral gap is observed in the Middle Infrared FEL Oscillator of FELiCHEM: the laser power falls down at the particular wavelength. Starting with the experimental data, this paper focuses on the simulation calculation and analysis of the effect from using the partial waveguide. The relationship between waveguide and spectral gap is revealed.

Poster TUPAB126 [1.063 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB126

About •

paper received ※ 17 May 2021 paper accepted ※ 14 June 2021 issue date ※ 21 August 2021

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

WEPAB228

Modelling and Counteracting Microbunching Instability in Spreader Lines of Radiofrequency and Plasma-Based Accelerators for Free-Electron Lasers

electron, bunching, laser, scattering

3165

G. Perosa
Università degli Studi di Trieste, Trieste, Italy
S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

High energy radiofrequency and plasma-driven accelerators target electron beam brightness suitable for x-ray free-electron lasers. Microbunching instability can be enhanced during beam transport through the spreader line from the accelerator to the undulator, degrading the brightness of the accelerated beam and therefore reducing the lasing efficiency. We present a semi-analytical model of the instability, benchmarked with experimental data at the FERMI free-electron laser, in the presence of intrabeam scattering and beam heating. Strategies for minimization of the instability both in conventional and plasma-based accelerators are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB228

About •

paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 02 September 2021

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

THPAB313

Drive Laser System for Shanghai Soft X-Ray Free Electron Laser

laser, FEL, electron, cathode

4403

L. Feng, C.L. Li, B. Liu, J.G. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China
X. Lu
ANL, Lemont, Illinois, USA
X.T. Wang, W.Y. Zhang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China

In this paper, we introduce the design and layout of the drive laser of Shanghai Soft X-ray Free Electron Laser (SXFEL). It is known that the temporal and spatial distribution of the drive laser is crucial for high-quality electron beams. The drive laser provides the laser pulse of 266nm wavelength and 8ps pulse duration for the photocathode, as well as 400nm wavelength, 2-20ps tunable pulse duration for the laser heater. For this purpose, there are mainly four parts in such system, including a third-harmonic generation device, pulse stretcher, image transmitted system, and laser optical module for laser heater. Finally, the measured results of the electron beam under this drive laser system are presented and discussed.

Poster THPAB313 [0.691 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB313

About •

paper received ※ 20 May 2021 paper accepted ※ 15 July 2021 issue date ※ 24 August 2021

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

FRXA06

Mitigation of Beam Instabilities in the Echo-Enabled Harmonic Generation Beamline for FLASH2020+

bunching, laser, electron, FEL

4514

F. Pannek, W. Hillert, D. Samoilenko
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Ackermann, E. Allaria, P. Niknejadi, G. Paraskaki, L. Schaper
DESY, Hamburg, Germany
M.A. Pop
MAX IV Laboratory, Lund University, Lund, Sweden

With the FLASH2020+ upgrade, one of the beamlines of the free-electron laser FLASH at DESY will be based on the Echo-Enabled Harmonic Generation (EEHG) seeding scheme and provide high-repetition-rate, coherent radiation down to 4 nm. To reach this wavelength, it is necessary to imprint intricate structures on the longitudinal phase space of the electron bunch at a very high harmonic of the seed laser wavelength, making the scheme potentially vulnerable to beam instabilities. Part of the beamline is a strong chicane, which is necessary to create the dispersion required by EEHG. Resulting effects such as Coherent Synchrotron Radiation (CSR) can be very detrimental for the bunching process and have to be taken into account already in the design of the beamline to ensure optimum FEL performance. We investigate and propose possible mitigation solutions to such instabilities in the FLASH2020+ parameter range.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA06

About •

paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 20 August 2021

Export •

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