FEL2017 - List of Authors (Garcia, B.W.)

Paper	Title	Page
MOP010	Constraints on Pulse Duration Produced by Echo-Enabled Harmonic Generation	46
	G. Penn LBNL, Berkeley, California, USA B.W. Garcia, E. Hemsing, G. Marcus SLAC, Menlo Park, California, USA
	Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract Nos. DE-AC02-05CH11231 and DE-AC02-76SF00515. Echo-enabled harmonic generation (EEHG) is well-suited for producing long, coherent pulses at high harmonics of seeding lasers. There have also been schemes proposed to adapt EEHG to output extremely short, sub-fs pulses by beam manipulations or through extremely short seed lasers, but the photon flux is generally lower than that produced by other schemes. For the standard EEHG layout, it is still interesting to consider different parameter regimes and evaluate how short a pulse can be generated. EEHG at high harmonics uses a large dispersive chicane which can change the relative distance of electrons by substantial distances, even longer than a typical FEL coherence length. We evaluate the ability to produce short pulses (in the femtosecond to 10-fs range) using a combination of theory and simulations.
	Poster MOP010 [0.451 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP010
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MOP016	Comparing FEL Codes for Advanced Configurations	60
	B.W. Garcia, G. Marcus SLAC, Menlo Park, California, USA L.T. Campbell STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom S. Reiche PSI, Villigen PSI, Switzerland
	Various FEL codes employ different approximations and strategies to model the FEL radiation generation process. Many codes perform averaging procedures over various length scales in order to simplify the underlying dynamics. As FELs are developed in more advanced configurations beyond simple SASE, the assumptions of some codes may be called into question. We compare the unaveraged code Puffin to averaged FEL codes including a new version of GENESIS in a variety of situations. In particular, we study a harmonic lasing setup, a High-Gain Harmonic Generation (HGHG) configuration modeled after the FERMI setup, and a potential Echo-Enabled Harmonic Generation (EEHG) configuration also at FERMI. We find the codes are in good agreement, although small discrepancies do exist.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP016
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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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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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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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Paper

Title

Page

Constraints on Pulse Duration Produced by Echo-Enabled Harmonic Generation

46

G. Penn
LBNL, Berkeley, California, USA
B.W. Garcia, E. Hemsing, G. Marcus
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract Nos. DE-AC02-05CH11231 and DE-AC02-76SF00515.
Echo-enabled harmonic generation (EEHG) is well-suited for producing long, coherent pulses at high harmonics of seeding lasers. There have also been schemes proposed to adapt EEHG to output extremely short, sub-fs pulses by beam manipulations or through extremely short seed lasers, but the photon flux is generally lower than that produced by other schemes. For the standard EEHG layout, it is still interesting to consider different parameter regimes and evaluate how short a pulse can be generated. EEHG at high harmonics uses a large dispersive chicane which can change the relative distance of electrons by substantial distances, even longer than a typical FEL coherence length. We evaluate the ability to produce short pulses (in the femtosecond to 10-fs range) using a combination of theory and simulations.

Poster MOP010 [0.451 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP010

Export •

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

MOP016

Comparing FEL Codes for Advanced Configurations

60

B.W. Garcia, G. Marcus
SLAC, Menlo Park, California, USA
L.T. Campbell
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
S. Reiche
PSI, Villigen PSI, Switzerland

Various FEL codes employ different approximations and strategies to model the FEL radiation generation process. Many codes perform averaging procedures over various length scales in order to simplify the underlying dynamics. As FELs are developed in more advanced configurations beyond simple SASE, the assumptions of some codes may be called into question. We compare the unaveraged code Puffin to averaged FEL codes including a new version of GENESIS in a variety of situations. In particular, we study a harmonic lasing setup, a High-Gain Harmonic Generation (HGHG) configuration modeled after the FERMI setup, and a potential Echo-Enabled Harmonic Generation (EEHG) configuration also at FERMI. We find the codes are in good agreement, although small discrepancies do exist.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP016

Export •

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

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

Export •

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

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)

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

Export •

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