FEL2017 - List of Authors (Huang, Z.)

Paper	Title	Page
MOP013	Hundred-Gigawatt X-Ray Self-Seeded High-Gain Harmonic Generation	53
	L. Zeng, S. Huang, K.X. Liu, W. Qin, G. Zhao PKU, Beijing, People's Republic of China Y. Ding, Z. Huang SLAC, Menlo Park, California, USA
	Self-seeded high-gain harmonic generation is a possible way to extend the wavelength of a soft x-ray free-electron laser (FEL). We have carried out simulation study on harmonic generation within the photon energy range from 2 keV to 4.5 keV, which is difficult to achieve due to a lack of monochromator materials. In this work, we demonstrate the third harmonic FEL with the fundamental wavelength at 1.52 nm. Our results shows that, by using undulator tapering technique, sub-terawatt narrow-bandwidth FEL output can be obtained.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP013
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MOP014	Harmonic Lasing Towards Shorter Wavelengths in Soft X-Ray Self-Seeding FELs	57
	L. Zeng, S. Huang, K.X. Liu, W. Qin, G. Zhao PKU, Beijing, People's Republic of China Y. Ding, Z. Huang SLAC, Menlo Park, California, USA
	In this paper, we study a simple harmonic lasing scheme to extend the wavelength of X-ray self-seeding FELs. The self-seeding amplifier is comprised of two stages. In the first stage, the fundamental radiation is amplified but well restricted below saturation, and simultaneously harmonic radiation is generated. In the second stage, the fundamental radiation is suppressed while the harmonic radiation is amplified to saturation. We performed a start-to-end simulation to demonstrate third harmonic lasing in a soft x-ray self-seeding FEL at the fundamental wavelength of 1.52 nm. Our simulations show that a stable narrow-band FEL at GW levels can be obtained.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP014
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MOP061	X-ray Regenerative Amplifier Free-Electron Laser Concepts for LCLS-II	192
	G. Marcus, Y. Ding, J.P. Duris, Y. Feng, Z. Huang, J. Krzywinski, T.J. Maxwell, D.F. Ratner, T.O. Raubenheimer SLAC, Menlo Park, California, USA K.-J. Kim, R.R. Lindberg, Yu. Shvyd'ko ANL, Argonne, Illinois, USA D.C. Nguyen LANL, Los Alamos, New Mexico, USA
	High-brightness electron beams that will drive the next generation of high-repetition rate X-ray FELs allow for the possibility of optical cavity-based feedback. One such cavity-based FEL concept is the Regenerative Amplifier Free-Electron Laser (RAFEL). This paper examines the design and performance of possible RAFEL configurations for LCLS-II. The results are primarily based on high-fidelity numerical particle simulations that show the production of high brightness, high average power, fully coherent, and stable X-ray pulses at LCLS-II using both the fundamental and harmonic FEL interactions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP061
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TUA03	Generation of High Power, Short X-Ray FEL Pulses
	M.W. Guetg, F.-J. Decker, Y. Ding, Z. Huang, A.A. Lutman, T.J. Maxwell SLAC, Menlo Park, California, USA
	X-ray Free Electron Lasers combine high pulse power, short pulse length, narrow bandwidth and a high degree of transverse coherence. Increasing the photon pulse power, while shortening the pulse length, is of key importance on the way to single molecule imaging. This letter shows experimental results at the Linac Coherent Light Source improving its power to more than 300 GW, while reducing the photon pulse length to 10fs. This was achieved by removing residual transverse-longitudinal centroid beam offsets and correction of dispersion when operating over 6 kA peak current.
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TUA05	Generating Subfemtosecond Hard X-Ray Pulses with Optimized Nonlinear Bunch Compression
	S. Huang PKU, Beijing, People's Republic of China Y. Ding, Y. Feng, E. Hemsing, Z. Huang, J. Krzywinski, A.A. Lutman, A. Marinelli, T.J. Maxwell, D. Zhu SLAC, Menlo Park, California, USA
	Funding: This work is supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515 and the National Key Research and Development Program of China (Grant No. 2016YFA0401904). A simple method for generating single-spike hard x-ray pulses in free-electron lasers (FELs) has been developed at the Linac Coherent Light Source (LCLS). By optimizing the electron bunch compression in experiments, we have obtained half of the hard x-ray FEL shots containing single-spike spectrum. At 5.6-keV photon energy, the single-spike shots have a mean pulse energy of about 10 J with 70% intensity fluctuation and the pulse width (full width at half maximum) is evaluated to be at 200-attosecond level.
	Slides TUA05 [3.854 MB]
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TUB01	Seeding Experiments and Seeding Options for LCLS II	219
	E. Hemsing, R.N. Coffee, W.M. Fawley, Y. Feng, B.W. Garcia, J.B. Hastings, Z. Huang, G. Marcus, D.F. Ratner, T.O. Raubenheimer SLAC, Menlo Park, California, USA G. Penn, R.W. Schoenlein LBNL, Berkeley, California, USA
	We discuss the present status of FEL seeding experiments toward the soft x-ray regime and on-going studies on possible seeding options for the high repetition soft x-ray line at LCLS-II. The seeding schemes include self-seeding, cascaded HGHG, and EEHG to reach the 1-2 nm regime with the highest possible brightness and minimal spectral pedestal. We describe relevant figures of merit, performance expectations, and potential issues.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUB01
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TUC03	High-Flux, Fully Coherent X-Ray FEL Oscillator
	K.-J. Kim, S.P. Kearney, T. Kolodziej, R.R. Lindberg, X. Shi, D. Shu, Yu. Shvyd'ko ANL, Argonne, Illinois, USA K.L.F. Bane, Y. Ding, P. Emma, W.M. Fawley, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus, T.J. Maxwell SLAC, Menlo Park, California, USA V.D. Blank, S. Terentiev TISNCM, Troitsk, Russia W.M. Fawley Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy C. Grizolli LNLS, Campinas, Brazil W. Qin PKU, Beijing, People's Republic of China S. Stoupin Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA J. Zemella DESY, Hamburg, Germany
	Funding: The ANL part of this work is supported by the U.S. DOE Office of Science under Contract No. DE-AC02-06CH11357 and the SLAC part under contract No. DE-AC02-76SF00515. By optimizing the parameters of the accelerator, undulator, and the optical cavity, an XFELO driven by an 8-GeV superconducting linac is predicted to produce 10^zEhNZeHn photons per pulse at the important photon energies around 14.4 keV.* This is an order of magnitude larger than that in previous designs. With a BW of 3 meV (FWHM), rep rate of 1 MHz, and taking into account the full coherence, the spectral brightness is then 2×10²⁶ photons per (mm2mr2 0.1\% BW), which is higher than any other source currently operating or anticipated in the future. Experiments at APS beam lines have shown that a high-quality diamond crystal can survive the power density (~15 kW/mm2) expected at the XFELO intra-cavity crystals preserving the high reflectivity.* The compound refractive lenses can serve as the focusing element. Adding an XFELO to the suite of other FEL sources will, at a minor incremental cost but with a major scientific payoff, significantly expand the scientific capabilities at superconducting linac-based XFEL facilities, such as the European XFEL, the proposed LCLS-II High Energy upgrade and the XFEL project in Shanghai. * W. Qin et al., this conference. R.R. Lindberg et al., Phys. Rev. ST Accel. Beams, vol 14, 403 (2011). * T. Kolodziej et al., this conference.
	Slides TUC03 [4.956 MB]
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TUC05	Start-to-End Simulations for an X-Ray FEL Oscillator at the LCLS-II and LCLS-II-HE	247
	W. Qin, K.L.F. Bane, Y. Ding, Z. Huang, G. Marcus, T.J. Maxwell SLAC, Menlo Park, California, USA S. Huang, K.X. Liu PKU, Beijing, People's Republic of China K.-J. Kim, R.R. Lindberg ANL, Argonne, Illinois, USA
	The proposed high repetition-rate electron beam from the LCLS-II and LCLS-II High Energy (LCLS-II-HE) upgrade are promising sources as drivers for an X-ray FEL Oscillator (XFELO) operating at both the harmonic and fundamental frequencies. In this contribution we present start-to-end simulations for an XFELO operating at the fifth harmonic with 4 GeV LCLS-II beam and at the fundamental with 8 GeV LCLS-II-HE beam. The electron beam longitudinal phase space is optimized by shaping the photoinjector laser and adjusting various machine parameters. The XFELO simulations show that high-flux output radiation pulses with 10¹⁰ photons and 3 meV (FWHM) spectral bandwidth can be obtained with the 8 GeV configuration.
	Slides TUC05 [3.802 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUC05
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WEP048	Coherent Undulator Radiation From a Kicked Electron Beam	515
	J.P. MacArthur, Z. Huang, J. Krzywinski, A.A. Lutman SLAC, Menlo Park, California, USA
	The properties of off-axis radiation from an electron beam that has been kicked off axis are relevant to recent Delta undualtor experiments at LCLS. We calculate the coherent emission from a microbunched beam in the far-field, and compare with simulation. We also present a mechanism for microbunches to tilt toward a new direction of propagation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP048
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WEP060	Characterizing Sub-Femtosecond X-ray Pulses from the Linac Coherent Light Source	535
	S. Li, R.N. Coffee, J. Cryan, K.H. Hegazy, Z. Huang, A. Marinelli, A. Natan, T. Osipov, D. Ray SLAC, Menlo Park, California, USA G. Guo Stanford University, Stanford, California, USA
	The development of sub-femtosecond x-ray capabilities at the Linac Coherent Light Source requires the implementation of time-domain diagnostics with attosecond (as) time resolution. Photoelectrons created by attosecond duration x-ray pulses in the presence of a strong-laser field are known to suffer an energy spread which depends on the relative phase of the strong-laser field at the time of ionization. This phenomenon can be exploited to measure the duration of these ultrashort x-ray pulses. We present an implementation which employs a circularly polarized infrared laser pulse and novel velocity map imaging design which maps the phase dependent momentum of the photoelectron onto a 2-D detector. In this paper, we present the novel co-linear VMI design, simulation of the photoelectron momentum distribution, and the reconstruction algorithm.
	Poster WEP060 [1.260 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP060
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THB03	High-Power, Narrow-Bandwidth THz Generation Using Laser-Electron Interaction in a Compact Accelerator
	Z. Huang, G. Marcus SLAC, Menlo Park, California, USA K. Kan ISIR, Osaka, Japan Z. Zhang TUB, Beijing, People's Republic of China
	We propose a method based on the slice energy-spread modulation to generate strong subpicosecond density bunching in high-intensity relativistic electron beams.* A laser pulse with periodic intensity envelope is used to modulate the slice energy spread of the electron beam, which can then be converted into density modulation after a dispersive section. In this paper, we study this method in a compact accelerator with electron energy on the order of 50 MeV. To interact with an infra-red laser, the modulation undulator is resonant with the laser at a harmonic frequency. We show the flexibility of this method to generate powerful, narrow-bandwidth radiation between 1-20 THz. The THz radiation can be generated at a very high-repetition rate that matches a high-repetition rate X-ray free-electron laser for pump-probe studies of novel materials. * Z. Zhang et al., Phys. Rev. Accel. Beams 20, 050701 (2017).
	Slides THB03 [3.539 MB]
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FRA01	Fresh-Slice X-Ray Free Electron Laser Schemes for Advanced X-Ray Applications
	A.A. Lutman, R.N. Coffee, Y. Ding, J.P. Duris, M.W. Guetg, Z. Huang, J. Krzywinski, J.P. MacArthur, A. Marinelli, T.J. Maxwell, S.P. Moeller, J. Zemella SLAC, Menlo Park, California, USA N. Berrah University of Connecticut, Storrs, Connecticut, USA C. Emma UCLA, Los Angeles, USA
	Funding: This work was supported by Department of Energy contract nos DE-AC02-76SF00515 and DE-SC0012376 The novel fresh-slice XFEL scheme grants control on the temporal slice of the electron bunch lasing in each undulator section. The technique relies on a time-dependent electron bunch trajectory impressed by the transverse wakefield of a corrugated structure and subsequent orbit manipulation in the undulator section. Fully saturated double pulses are produced in two different undulator sections. The wavelength of each pulse is controlled by the undulator magnetic strength and the delay between the pulses can be scanned from a few femtosecond advance of the pulse generated on the bunch head in the second section to a picosecond delay provided by the magnetic chicane. Three-color saturated pulses are demonstrated by using three undulator sections and the polarization of the pulse generated in the last section can be controlled by the variable polarization Delta undulator. In this work we also show the early results for the first multi-stage amplification scheme, producing ultra-short single-pulses with a 100-GW power level in the soft X-rays. The multi-stage amplification is also demonstrated to improve the performance in power and pulse duration control for the two-color FEL scheme.
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FRB01	Time-Domain Analysis of Attosecond Pulse Generation in an X-Ray Free-Electron Laser	569
	P. Baxevanis, Z. Huang, A. Marinelli SLAC, Menlo Park, California, USA
	The method of enhanced self-amplified spontaneous emission (eSASE) is one of the strongest candidates for the generation of sub-femtosecond X-ray pulses in a free-electron laser. The optimization of an eSASE experiment involves many independent parameters, which makes the exploration of the parameter space with 3-D simulations computationally intensive. Therefore, a robust theoretical analysis of this problem is extremely desirable. We provide a self-consistent, analytical treatment of such a configuration using a one-dimensional, time-dependent FEL model that includes the key effects of linear e-beam chirp and linear undulator taper. Verified via comparison with numerical simulation, our formalism is also utilized in parameter studies that seek to determine the optimum setup of the FEL.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB01
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Paper

Title

Page

Hundred-Gigawatt X-Ray Self-Seeded High-Gain Harmonic Generation

53

L. Zeng, S. Huang, K.X. Liu, W. Qin, G. Zhao
PKU, Beijing, People's Republic of China
Y. Ding, Z. Huang
SLAC, Menlo Park, California, USA

Self-seeded high-gain harmonic generation is a possible way to extend the wavelength of a soft x-ray free-electron laser (FEL). We have carried out simulation study on harmonic generation within the photon energy range from 2 keV to 4.5 keV, which is difficult to achieve due to a lack of monochromator materials. In this work, we demonstrate the third harmonic FEL with the fundamental wavelength at 1.52 nm. Our results shows that, by using undulator tapering technique, sub-terawatt narrow-bandwidth FEL output can be obtained.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP013

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MOP014

Harmonic Lasing Towards Shorter Wavelengths in Soft X-Ray Self-Seeding FELs

57

L. Zeng, S. Huang, K.X. Liu, W. Qin, G. Zhao
PKU, Beijing, People's Republic of China
Y. Ding, Z. Huang
SLAC, Menlo Park, California, USA

In this paper, we study a simple harmonic lasing scheme to extend the wavelength of X-ray self-seeding FELs. The self-seeding amplifier is comprised of two stages. In the first stage, the fundamental radiation is amplified but well restricted below saturation, and simultaneously harmonic radiation is generated. In the second stage, the fundamental radiation is suppressed while the harmonic radiation is amplified to saturation. We performed a start-to-end simulation to demonstrate third harmonic lasing in a soft x-ray self-seeding FEL at the fundamental wavelength of 1.52 nm. Our simulations show that a stable narrow-band FEL at GW levels can be obtained.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP014

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MOP061

X-ray Regenerative Amplifier Free-Electron Laser Concepts for LCLS-II

192

G. Marcus, Y. Ding, J.P. Duris, Y. Feng, Z. Huang, J. Krzywinski, T.J. Maxwell, D.F. Ratner, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
K.-J. Kim, R.R. Lindberg, Yu. Shvyd'ko
ANL, Argonne, Illinois, USA
D.C. Nguyen
LANL, Los Alamos, New Mexico, USA

High-brightness electron beams that will drive the next generation of high-repetition rate X-ray FELs allow for the possibility of optical cavity-based feedback. One such cavity-based FEL concept is the Regenerative Amplifier Free-Electron Laser (RAFEL). This paper examines the design and performance of possible RAFEL configurations for LCLS-II. The results are primarily based on high-fidelity numerical particle simulations that show the production of high brightness, high average power, fully coherent, and stable X-ray pulses at LCLS-II using both the fundamental and harmonic FEL interactions.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP061

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TUA03

Generation of High Power, Short X-Ray FEL Pulses

M.W. Guetg, F.-J. Decker, Y. Ding, Z. Huang, A.A. Lutman, T.J. Maxwell
SLAC, Menlo Park, California, USA

X-ray Free Electron Lasers combine high pulse power, short pulse length, narrow bandwidth and a high degree of transverse coherence. Increasing the photon pulse power, while shortening the pulse length, is of key importance on the way to single molecule imaging. This letter shows experimental results at the Linac Coherent Light Source improving its power to more than 300 GW, while reducing the photon pulse length to 10fs. This was achieved by removing residual transverse-longitudinal centroid beam offsets and correction of dispersion when operating over 6 kA peak current.

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TUA05

Generating Subfemtosecond Hard X-Ray Pulses with Optimized Nonlinear Bunch Compression

S. Huang
PKU, Beijing, People's Republic of China
Y. Ding, Y. Feng, E. Hemsing, Z. Huang, J. Krzywinski, A.A. Lutman, A. Marinelli, T.J. Maxwell, D. Zhu
SLAC, Menlo Park, California, USA

Funding: This work is supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515 and the National Key Research and Development Program of China (Grant No. 2016YFA0401904).
A simple method for generating single-spike hard x-ray pulses in free-electron lasers (FELs) has been developed at the Linac Coherent Light Source (LCLS). By optimizing the electron bunch compression in experiments, we have obtained half of the hard x-ray FEL shots containing single-spike spectrum. At 5.6-keV photon energy, the single-spike shots have a mean pulse energy of about 10 J with 70% intensity fluctuation and the pulse width (full width at half maximum) is evaluated to be at 200-attosecond level.

Slides TUA05 [3.854 MB]

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TUB01

Seeding Experiments and Seeding Options for LCLS II

219

E. Hemsing, R.N. Coffee, W.M. Fawley, Y. Feng, B.W. Garcia, J.B. Hastings, Z. Huang, G. Marcus, D.F. Ratner, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
G. Penn, R.W. Schoenlein
LBNL, Berkeley, California, USA

We discuss the present status of FEL seeding experiments toward the soft x-ray regime and on-going studies on possible seeding options for the high repetition soft x-ray line at LCLS-II. The seeding schemes include self-seeding, cascaded HGHG, and EEHG to reach the 1-2 nm regime with the highest possible brightness and minimal spectral pedestal. We describe relevant figures of merit, performance expectations, and potential issues.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUB01

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TUC03

High-Flux, Fully Coherent X-Ray FEL Oscillator

K.-J. Kim, S.P. Kearney, T. Kolodziej, R.R. Lindberg, X. Shi, D. Shu, Yu. Shvyd'ko
ANL, Argonne, Illinois, USA
K.L.F. Bane, Y. Ding, P. Emma, W.M. Fawley, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus, T.J. Maxwell
SLAC, Menlo Park, California, USA
V.D. Blank, S. Terentiev
TISNCM, Troitsk, Russia
W.M. Fawley
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
C. Grizolli
LNLS, Campinas, Brazil
W. Qin
PKU, Beijing, People's Republic of China
S. Stoupin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J. Zemella
DESY, Hamburg, Germany

Funding: The ANL part of this work is supported by the U.S. DOE Office of Science under Contract No. DE-AC02-06CH11357 and the SLAC part under contract No. DE-AC02-76SF00515.
By optimizing the parameters of the accelerator, undulator, and the optical cavity, an XFELO driven by an 8-GeV superconducting linac is predicted to produce 10^zEhNZeHn photons per pulse at the important photon energies around 14.4 keV.* This is an order of magnitude larger than that in previous designs.** With a BW of 3 meV (FWHM), rep rate of 1 MHz, and taking into account the full coherence, the spectral brightness is then 2×10²⁶ photons per (mm2mr2 0.1\% BW), which is higher than any other source currently operating or anticipated in the future. Experiments at APS beam lines have shown that a high-quality diamond crystal can survive the power density (~15 kW/mm2) expected at the XFELO intra-cavity crystals preserving the high reflectivity.*** The compound refractive lenses can serve as the focusing element. Adding an XFELO to the suite of other FEL sources will, at a minor incremental cost but with a major scientific payoff, significantly expand the scientific capabilities at superconducting linac-based XFEL facilities, such as the European XFEL, the proposed LCLS-II High Energy upgrade and the XFEL project in Shanghai.
* W. Qin et al., this conference.
** R.R. Lindberg et al., Phys. Rev. ST Accel. Beams, vol 14, 403 (2011).
*** T. Kolodziej et al., this conference.

Slides TUC03 [4.956 MB]

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TUC05

Start-to-End Simulations for an X-Ray FEL Oscillator at the LCLS-II and LCLS-II-HE

247

W. Qin, K.L.F. Bane, Y. Ding, Z. Huang, G. Marcus, T.J. Maxwell
SLAC, Menlo Park, California, USA
S. Huang, K.X. Liu
PKU, Beijing, People's Republic of China
K.-J. Kim, R.R. Lindberg
ANL, Argonne, Illinois, USA

The proposed high repetition-rate electron beam from the LCLS-II and LCLS-II High Energy (LCLS-II-HE) upgrade are promising sources as drivers for an X-ray FEL Oscillator (XFELO) operating at both the harmonic and fundamental frequencies. In this contribution we present start-to-end simulations for an XFELO operating at the fifth harmonic with 4 GeV LCLS-II beam and at the fundamental with 8 GeV LCLS-II-HE beam. The electron beam longitudinal phase space is optimized by shaping the photoinjector laser and adjusting various machine parameters. The XFELO simulations show that high-flux output radiation pulses with 10¹⁰ photons and 3 meV (FWHM) spectral bandwidth can be obtained with the 8 GeV configuration.

Slides TUC05 [3.802 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUC05

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WEP048

Coherent Undulator Radiation From a Kicked Electron Beam

515

J.P. MacArthur, Z. Huang, J. Krzywinski, A.A. Lutman
SLAC, Menlo Park, California, USA

The properties of off-axis radiation from an electron beam that has been kicked off axis are relevant to recent Delta undualtor experiments at LCLS. We calculate the coherent emission from a microbunched beam in the far-field, and compare with simulation. We also present a mechanism for microbunches to tilt toward a new direction of propagation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP048

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WEP060

Characterizing Sub-Femtosecond X-ray Pulses from the Linac Coherent Light Source

535

S. Li, R.N. Coffee, J. Cryan, K.H. Hegazy, Z. Huang, A. Marinelli, A. Natan, T. Osipov, D. Ray
SLAC, Menlo Park, California, USA
G. Guo
Stanford University, Stanford, California, USA

The development of sub-femtosecond x-ray capabilities at the Linac Coherent Light Source requires the implementation of time-domain diagnostics with attosecond (as) time resolution. Photoelectrons created by attosecond duration x-ray pulses in the presence of a strong-laser field are known to suffer an energy spread which depends on the relative phase of the strong-laser field at the time of ionization. This phenomenon can be exploited to measure the duration of these ultrashort x-ray pulses. We present an implementation which employs a circularly polarized infrared laser pulse and novel velocity map imaging design which maps the phase dependent momentum of the photoelectron onto a 2-D detector. In this paper, we present the novel co-linear VMI design, simulation of the photoelectron momentum distribution, and the reconstruction algorithm.

Poster WEP060 [1.260 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP060

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THB03

High-Power, Narrow-Bandwidth THz Generation Using Laser-Electron Interaction in a Compact Accelerator

Z. Huang, G. Marcus
SLAC, Menlo Park, California, USA
K. Kan
ISIR, Osaka, Japan
Z. Zhang
TUB, Beijing, People's Republic of China

We propose a method based on the slice energy-spread modulation to generate strong subpicosecond density bunching in high-intensity relativistic electron beams.* A laser pulse with periodic intensity envelope is used to modulate the slice energy spread of the electron beam, which can then be converted into density modulation after a dispersive section. In this paper, we study this method in a compact accelerator with electron energy on the order of 50 MeV. To interact with an infra-red laser, the modulation undulator is resonant with the laser at a harmonic frequency. We show the flexibility of this method to generate powerful, narrow-bandwidth radiation between 1-20 THz. The THz radiation can be generated at a very high-repetition rate that matches a high-repetition rate X-ray free-electron laser for pump-probe studies of novel materials.
* Z. Zhang et al., Phys. Rev. Accel. Beams 20, 050701 (2017).

Slides THB03 [3.539 MB]

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FRA01

Fresh-Slice X-Ray Free Electron Laser Schemes for Advanced X-Ray Applications

A.A. Lutman, R.N. Coffee, Y. Ding, J.P. Duris, M.W. Guetg, Z. Huang, J. Krzywinski, J.P. MacArthur, A. Marinelli, T.J. Maxwell, S.P. Moeller, J. Zemella
SLAC, Menlo Park, California, USA
N. Berrah
University of Connecticut, Storrs, Connecticut, USA
C. Emma
UCLA, Los Angeles, USA

Funding: This work was supported by Department of Energy contract nos DE-AC02-76SF00515 and DE-SC0012376
The novel fresh-slice XFEL scheme grants control on the temporal slice of the electron bunch lasing in each undulator section. The technique relies on a time-dependent electron bunch trajectory impressed by the transverse wakefield of a corrugated structure and subsequent orbit manipulation in the undulator section. Fully saturated double pulses are produced in two different undulator sections. The wavelength of each pulse is controlled by the undulator magnetic strength and the delay between the pulses can be scanned from a few femtosecond advance of the pulse generated on the bunch head in the second section to a picosecond delay provided by the magnetic chicane. Three-color saturated pulses are demonstrated by using three undulator sections and the polarization of the pulse generated in the last section can be controlled by the variable polarization Delta undulator. In this work we also show the early results for the first multi-stage amplification scheme, producing ultra-short single-pulses with a 100-GW power level in the soft X-rays. The multi-stage amplification is also demonstrated to improve the performance in power and pulse duration control for the two-color FEL scheme.

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FRB01

Time-Domain Analysis of Attosecond Pulse Generation in an X-Ray Free-Electron Laser

569

P. Baxevanis, Z. Huang, A. Marinelli
SLAC, Menlo Park, California, USA

The method of enhanced self-amplified spontaneous emission (eSASE) is one of the strongest candidates for the generation of sub-femtosecond X-ray pulses in a free-electron laser. The optimization of an eSASE experiment involves many independent parameters, which makes the exploration of the parameter space with 3-D simulations computationally intensive. Therefore, a robust theoretical analysis of this problem is extremely desirable. We provide a self-consistent, analytical treatment of such a configuration using a one-dimensional, time-dependent FEL model that includes the key effects of linear e-beam chirp and linear undulator taper. Verified via comparison with numerical simulation, our formalism is also utilized in parameter studies that seek to determine the optimum setup of the FEL.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB01

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