FEL2017 - List of Authors (Raubenheimer, T.O.)

Paper	Title	Page
MOP017	Echo-Enabled Harmonic Generation Results with Energy Chirp	64
	B.W. Garcia, M.P. Dunning, C. Hast, E. Hemsing, T.O. Raubenheimer, G. Stupakov SLAC, Menlo Park, California, USA D. Xiang Shanghai Jiao Tong University, Shanghai, People's Republic of China
	We report here on several experimental results from the NLCTA at SLAC involving chirped Echo-Enabled Harmonic Generation (EEHG) beams. We directly observe the sensitivity of the different n EEHG modes to a linear beam chirp. This differential sensitivity results in a multi-color EEHG signal which can be fine tuned through the EEHG parameters and beam chirp. We also generate a beam which, due to a timing delay between the two seed lasers, contains both regions of EEHG and High-Gain Harmonic Generation (HGHG) bunching. The two regions are clearly separated on the resulting radiation spectrum due to a linear energy chirp, and one can simultaneously monitor their sensitivities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP017
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MOP018	Distributed Self-Seeding Scheme for LCLS-II	68
	C. Yang, Y. Feng, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou SLAC, Menlo Park, California, USA B. Yang University of Texas at Arlington, Arlington, USA
	Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164. Self-seeding is a successful approach for generating high-brightness x-ray free electron laser (XFEL). A single-crystal monochromator in-between the undulator sections to generate a coherent seed is adopted in LCLS. However, for a high-repetition rate machine like LCLS-II, the crystal monochromator in current setup cannot sustain the high average power; hence a distributed self-seeding scheme utilizing multi-stages is necessary. Based on the criteria set on the crystal, the maximum allowed x-ray energy deposited in the crystal will determine the machine configuration for such a distributed self-seeding scheme. In this paper, a distributed self-seeding configuration is optimized for LCLS-II type projects in the hard x-ray FEL energy regime. The study is carried out based on numerical simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP018
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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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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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TUB04	Recent On-Line Taper Optimization on LCLS	229
	J. Wu, X. Huang, T.O. Raubenheimer SLAC, Menlo Park, California, USA A. Scheinker LANL, Los Alamos, New Mexico, USA
	Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164. High-brightness XFELs are demanding for many users, in particular for certain types of imaging applications. Self-seeding XFELs can respond to a heavily tapered undulator more effectively, therefore seeded tapered FELs are considered as a path to high-power FELs in the terawatts level. Due to many effects, including the synchrotron motion, the optimization of the taper profile is intrinsically multi-dimensional and computationally expensive. With an operating XFEL, such as LCLS, the on-line optimization becomes more economical than numerical simulation. Here we report recent on-line taper optimization on LCLS taking full advantages of nonlinear optimizers as well as up-to-date development of artificial intelligence: deep machine learning and neural networks.
	Slides TUB04 [8.227 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUB04
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TUP024	Stochastic Effects from Classical 3D Synchrotron Radiation	292
	B.W. Garcia, T.O. Raubenheimer SLAC, Menlo Park, California, USA R.D. Ryne LBNL, Berkeley, California, USA
	In most cases, the one-dimensional coherent synchrotron radiation wakefield gives an excellent approximation to the total coherent effect due to classical synchrotron radiation in bend magnets. However, full particle Liénard-Wiechert simulations have revealed that there is non-numerical, stochastic noise which generates fluctuations about the approximate 1D solution. We present a model for this stochastic term in which this noise is due to long-range interaction with a discrete number of synchrotron radiation cones. The nature of this noise and how it depends on the 3D dimensions of the beam are explored.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP024
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TUP027	Cancellation of Coherent Synchrotron Radiation Kicks at LCLS	296
	D. Khan, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	In this paper, we look at the cancellation of Coherent Synchrotron Radiation (CSR) induced emittance growth using a phase-advance manipulation technique pioneered by R. Hajima, and extended in the Courant-Snyder formalism by S. Di Mitri. Bending systems in a linear accelerator are essential for beam transport and bunch compression. With the ever-growing demands of high-energy, short wavelength free electron laser (FEL) drivers, the CSR effect has emerged to be a detrimental factor in emittance stability. Under linear approximation, it is showed that the CSR driven dispersive kicks in successive bending magnet systems can, with proper balancing of the linac optics, cancel each other to nullify transverse emittance growth. This technique of optics balancing in the constant bunch length regime is the focus of this paper. We will present our findings for the emittance measurements generated in Elegant simulations for the current LCLS-I dogleg system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP027
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TUP028	Approximated Expressions for the Coherent Synchrotron Radiation Effect in Bending Magnets	300
	D. Khan, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	In this paper, we describe the development of simplified analytic expressions for the Coherent Synchrotron Radiation's (CSR) root-mean-square induced energy spread, typically found in the bending magnets of short bunch-length charged particle accelerators. The expressions are derived for a Gaussian longitudinal bunch distribution and compared with the full-rigor CSR wakefield integral expressions while entering, traversing and exiting a bending magnet. The validity of the expressions are then tested against ELEGANT with the simulation of an unchirped beam traveling across a bending magnet into a drift section, and the second stage bunch compressor (BC2) of the proposed LCLS-II beamline.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP028
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TUP030	An Emittance-Preservation Study of a Five-Bend Chicane for the LCLS-II-HE Beamline	305
	D. Khan, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	The Linac Coherent Light Source II (LCLS-II) is an upgrade intended to advance the great success of its predecessor, LCLS-I, to maintain its position at the forefront of X-ray science. The introduction of a niobium-metal superconducting linac for LCLS-II not only increases the repetition rate to the MHz level (from 120 Hz), but also boasts an average brightness many orders higher (~10,000) than that of LCLS-I. Though, these improvements do not come without a price: the peak brightness suffers by a factor of 10, owing its degradation to the impact of Coherent Synchrotron Radiation (CSR) diminishing the peak current of the beam in the second bunch compressor (BC2). In this paper, we discuss the impact of implementing a plug-compatible 5-bend chicane for BC2 on the beam's emittance dilution for a high-energy, low-emittance configuration of LCLS-II (LCLS-II-HE). The results are compared with that of a standard 4-bend chicane under various settings in Elegant and CSRTrack.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP030
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TUP057	Measurement of Short-Wavelength High-Gain FEL Temporal Coherence Length by a Phase Shifter	344
	G. Zhou IHEP, Beijing, People's Republic of China W. Liu USTC/NSRL, Hefei, Anhui, People's Republic of China W. Qin, T.O. Raubenheimer, J. Wu, C. Yang SLAC, Menlo Park, California, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA B. Yang University of Texas at Arlington, Arlington, USA M. Yoon POSTECH, Pohang, Kyungbuk, Republic of Korea
	Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164. Short-wavelength high-gain free-electron lasers (FELs) are now well established as a source of ultra-fast, ultra-brightness, longitudinally partial coherent light. Since coherence is one of the fundamental properties of light source, so continual effort is devoted to high-gain free-electron laser coherence measurements. In this work, we propose a possible approach, employing a phase shifter to induce electron beam delay to measure the temporal coherence length. Simple analysis, numerical simulation and preliminary experimental results are presented. This approach can be robust and independent of frequency.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP057
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TUP058	Slippage-Enhanced SASE FEL	348
	J. Wu, A. Brachmann, K. Fang, A. Marinelli, C. Pellegrini, T.O. Raubenheimer, C.-Y. Tsai, C. Yang, M. Yoon, G. Zhou SLAC, Menlo Park, California, USA H.-S. Kang, G. Kim, I.H. Nam PAL, Pohang, Republic of Korea B. Yang University of Texas at Arlington, Arlington, USA
	Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164. High-brightness XFEL is demanding for many users, in particular for certain types of imaging applications. Seeded FELs including self-seeding XFELs were successfully demonstrated. Alternative approaches by enhancing slippage between the x-ray pulse and the electron bunch were also demonstrated. This class of Slippage-enhanced SASE (SeSASE) schemes can be unique for FEL spectral range between 1.5 keV to 4 keV where neither grating-based soft x-ray self-seeding nor crystal-based hard x-ray self-seeding can easily access. SeSASE can provide high-brightness XFEL for high repetition rate machines not suffering from heat load on the crystal monochromator. We report start-to-end simulation results for LCLS-II project and PAL-XFEL project with study on tolerance. Performance comparison between SaSASE FEL and self-seeding FEL in the overlapping frequency range is also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP058
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THB05	Ion Effects in LCLS and LCLS-II
	T.O. Raubenheimer SLAC, Menlo Park, California, USA
	Funding: This work supported in part by the Department of Energy Contract DE-AC02-76-SF00515. The effect of ions are evaluated in LCLS and LCLS-II. X-ray FEL's require high-brightness beams, that generate very high internal beam fields which can potentially lead to tunneling ionization. The FEL performance is sensitive to betatron mismatches which can arise from the focusing due to ions. In LCLS, both collisional and tunneling ionization may have an impact on single electron bunches while LCLS-II will have the additional complication of trapped ions in the MHz-rate multi-bunch trains. Analytic and simulation results for the LCLS and LCLS-II are presented and scalings are described to estimate the effects in other X-ray FEL's.
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Paper

Title

Page

Echo-Enabled Harmonic Generation Results with Energy Chirp

64

B.W. Garcia, M.P. Dunning, C. Hast, E. Hemsing, T.O. Raubenheimer, G. Stupakov
SLAC, Menlo Park, California, USA
D. Xiang
Shanghai Jiao Tong University, Shanghai, People's Republic of China

We report here on several experimental results from the NLCTA at SLAC involving chirped Echo-Enabled Harmonic Generation (EEHG) beams. We directly observe the sensitivity of the different n EEHG modes to a linear beam chirp. This differential sensitivity results in a multi-color EEHG signal which can be fine tuned through the EEHG parameters and beam chirp. We also generate a beam which, due to a timing delay between the two seed lasers, contains both regions of EEHG and High-Gain Harmonic Generation (HGHG) bunching. The two regions are clearly separated on the resulting radiation spectrum due to a linear energy chirp, and one can simultaneously monitor their sensitivities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP017

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MOP018

Distributed Self-Seeding Scheme for LCLS-II

68

C. Yang, Y. Feng, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou
SLAC, Menlo Park, California, USA
B. Yang
University of Texas at Arlington, Arlington, USA

Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Self-seeding is a successful approach for generating high-brightness x-ray free electron laser (XFEL). A single-crystal monochromator in-between the undulator sections to generate a coherent seed is adopted in LCLS. However, for a high-repetition rate machine like LCLS-II, the crystal monochromator in current setup cannot sustain the high average power; hence a distributed self-seeding scheme utilizing multi-stages is necessary. Based on the criteria set on the crystal, the maximum allowed x-ray energy deposited in the crystal will determine the machine configuration for such a distributed self-seeding scheme. In this paper, a distributed self-seeding configuration is optimized for LCLS-II type projects in the hard x-ray FEL energy regime. The study is carried out based on numerical simulation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP018

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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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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

Export •

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

TUB04

Recent On-Line Taper Optimization on LCLS

229

J. Wu, X. Huang, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
A. Scheinker
LANL, Los Alamos, New Mexico, USA

Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
High-brightness XFELs are demanding for many users, in particular for certain types of imaging applications. Self-seeding XFELs can respond to a heavily tapered undulator more effectively, therefore seeded tapered FELs are considered as a path to high-power FELs in the terawatts level. Due to many effects, including the synchrotron motion, the optimization of the taper profile is intrinsically multi-dimensional and computationally expensive. With an operating XFEL, such as LCLS, the on-line optimization becomes more economical than numerical simulation. Here we report recent on-line taper optimization on LCLS taking full advantages of nonlinear optimizers as well as up-to-date development of artificial intelligence: deep machine learning and neural networks.

Slides TUB04 [8.227 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUB04

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TUP024

Stochastic Effects from Classical 3D Synchrotron Radiation

292

B.W. Garcia, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
R.D. Ryne
LBNL, Berkeley, California, USA

In most cases, the one-dimensional coherent synchrotron radiation wakefield gives an excellent approximation to the total coherent effect due to classical synchrotron radiation in bend magnets. However, full particle Liénard-Wiechert simulations have revealed that there is non-numerical, stochastic noise which generates fluctuations about the approximate 1D solution. We present a model for this stochastic term in which this noise is due to long-range interaction with a discrete number of synchrotron radiation cones. The nature of this noise and how it depends on the 3D dimensions of the beam are explored.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP024

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TUP027

Cancellation of Coherent Synchrotron Radiation Kicks at LCLS

296

D. Khan, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

In this paper, we look at the cancellation of Coherent Synchrotron Radiation (CSR) induced emittance growth using a phase-advance manipulation technique pioneered by R. Hajima, and extended in the Courant-Snyder formalism by S. Di Mitri. Bending systems in a linear accelerator are essential for beam transport and bunch compression. With the ever-growing demands of high-energy, short wavelength free electron laser (FEL) drivers, the CSR effect has emerged to be a detrimental factor in emittance stability. Under linear approximation, it is showed that the CSR driven dispersive kicks in successive bending magnet systems can, with proper balancing of the linac optics, cancel each other to nullify transverse emittance growth. This technique of optics balancing in the constant bunch length regime is the focus of this paper. We will present our findings for the emittance measurements generated in Elegant simulations for the current LCLS-I dogleg system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP027

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TUP028

Approximated Expressions for the Coherent Synchrotron Radiation Effect in Bending Magnets

300

D. Khan, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

In this paper, we describe the development of simplified analytic expressions for the Coherent Synchrotron Radiation's (CSR) root-mean-square induced energy spread, typically found in the bending magnets of short bunch-length charged particle accelerators. The expressions are derived for a Gaussian longitudinal bunch distribution and compared with the full-rigor CSR wakefield integral expressions while entering, traversing and exiting a bending magnet. The validity of the expressions are then tested against ELEGANT with the simulation of an unchirped beam traveling across a bending magnet into a drift section, and the second stage bunch compressor (BC2) of the proposed LCLS-II beamline.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP028

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

TUP030

An Emittance-Preservation Study of a Five-Bend Chicane for the LCLS-II-HE Beamline

305

D. Khan, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The Linac Coherent Light Source II (LCLS-II) is an upgrade intended to advance the great success of its predecessor, LCLS-I, to maintain its position at the forefront of X-ray science. The introduction of a niobium-metal superconducting linac for LCLS-II not only increases the repetition rate to the MHz level (from 120 Hz), but also boasts an average brightness many orders higher (~10,000) than that of LCLS-I. Though, these improvements do not come without a price: the peak brightness suffers by a factor of 10, owing its degradation to the impact of Coherent Synchrotron Radiation (CSR) diminishing the peak current of the beam in the second bunch compressor (BC2). In this paper, we discuss the impact of implementing a plug-compatible 5-bend chicane for BC2 on the beam's emittance dilution for a high-energy, low-emittance configuration of LCLS-II (LCLS-II-HE). The results are compared with that of a standard 4-bend chicane under various settings in Elegant and CSRTrack.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP030

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TUP057

Measurement of Short-Wavelength High-Gain FEL Temporal Coherence Length by a Phase Shifter

344

G. Zhou
IHEP, Beijing, People's Republic of China
W. Liu
USTC/NSRL, Hefei, Anhui, People's Republic of China
W. Qin, T.O. Raubenheimer, J. Wu, C. Yang
SLAC, Menlo Park, California, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
B. Yang
University of Texas at Arlington, Arlington, USA
M. Yoon
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Short-wavelength high-gain free-electron lasers (FELs) are now well established as a source of ultra-fast, ultra-brightness, longitudinally partial coherent light. Since coherence is one of the fundamental properties of light source, so continual effort is devoted to high-gain free-electron laser coherence measurements. In this work, we propose a possible approach, employing a phase shifter to induce electron beam delay to measure the temporal coherence length. Simple analysis, numerical simulation and preliminary experimental results are presented. This approach can be robust and independent of frequency.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP057

Export •

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

TUP058

Slippage-Enhanced SASE FEL

348

J. Wu, A. Brachmann, K. Fang, A. Marinelli, C. Pellegrini, T.O. Raubenheimer, C.-Y. Tsai, C. Yang, M. Yoon, G. Zhou
SLAC, Menlo Park, California, USA
H.-S. Kang, G. Kim, I.H. Nam
PAL, Pohang, Republic of Korea
B. Yang
University of Texas at Arlington, Arlington, USA

Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
High-brightness XFEL is demanding for many users, in particular for certain types of imaging applications. Seeded FELs including self-seeding XFELs were successfully demonstrated. Alternative approaches by enhancing slippage between the x-ray pulse and the electron bunch were also demonstrated. This class of Slippage-enhanced SASE (SeSASE) schemes can be unique for FEL spectral range between 1.5 keV to 4 keV where neither grating-based soft x-ray self-seeding nor crystal-based hard x-ray self-seeding can easily access. SeSASE can provide high-brightness XFEL for high repetition rate machines not suffering from heat load on the crystal monochromator. We report start-to-end simulation results for LCLS-II project and PAL-XFEL project with study on tolerance. Performance comparison between SaSASE FEL and self-seeding FEL in the overlapping frequency range is also presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP058

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THB05

Ion Effects in LCLS and LCLS-II

T.O. Raubenheimer
SLAC, Menlo Park, California, USA

Funding: This work supported in part by the Department of Energy Contract DE-AC02-76-SF00515.
The effect of ions are evaluated in LCLS and LCLS-II. X-ray FEL's require high-brightness beams, that generate very high internal beam fields which can potentially lead to tunneling ionization. The FEL performance is sensitive to betatron mismatches which can arise from the focusing due to ions. In LCLS, both collisional and tunneling ionization may have an impact on single electron bunches while LCLS-II will have the additional complication of trapped ions in the MHz-rate multi-bunch trains. Analytic and simulation results for the LCLS and LCLS-II are presented and scalings are described to estimate the effects in other X-ray FEL's.

Export •

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