IPAC2016 - List of Authors (Ratner, D.F.)

Paper	Title	Page
TUOCA01	LCLS Bunch Compressor Configuration Study for Soft X-ray Operation	1037
	S. Li, Y. Ding, Z. Huang, A. Marinelli, T.J. Maxwell, D.F. Ratner, F. Zhou SLAC, Menlo Park, California, USA C. Behrens DESY, Hamburg, Germany
	The microbunching instability (MBI) is a well-known problem for high brightness electron beams and has been observed at accelerator facilities around the world. Free-electron lasers (FELs) are particularly susceptible to MBI, which can distort the longitudinal phase space and increase the beam's slice energy spread (SES). Past studies of MBI at the Linac Coherent Light Source (LCLS) relied on optical transition radiation to infer the existence of microbunching. With the development of the x-band transverse deflecting cavity (XTCAV), we can for the first time directly image the longitudinal phase space at the end of the accelerator and complete a comprehensive study of MBI, revealing both detailed MBI behavior as well as insights into mitigation schemes [1]. The fine time resolution of the XTCAV also provides the first LCLS measurements of the final SES, a critical parameter for many advanced FEL schemes. Detailed MBI and SES measurements can aid in understanding MBI mechanisms, benchmarking simulation codes, and designing future high-brightness accelerators.
	Slides TUOCA01 [4.436 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOCA01
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TUXB01	High Power Radiation Sources using the Steady-state Microbunching Mechanism	1048
	A. Chao, E. Granados, X. Huang, D.F. Ratner SLAC, Menlo Park, California, USA H.W. Luo NTHU, Hsinchu, Taiwan
	The mechanism of steady-state microbunching (SSMB) was proposed for providing high power coherent radiation using electron storage rings. The mechanism follows closely the RF bunching in conventional storage rings, except that the energy modulation of by an RF system at a microwave wavelength is replaced by a seeded laser in an undulator at an optical wavelength. No FEL mechanism, and thus no FEL energy heating, is invoked. The basic idea is firstly to make the beam microbunched so that its radiation becomes coherent, and secondly to make the microbunching a steady state so that the coherent radiation is maintained at every turn. The combination of the high repetition rate of a storage ring and the enhanced radiation power by a factor of N (the number of electrons in the microbunches within one coherence length) opens the possibility as well as challenges of very high power SSMB sources. To explore its potential reach, we apply SSMB to the infrared, deep ultraviolet and EUV regions and estimate their respective power levels using SPEAR3 as example. Several variants of the SSMB schemes are discussed. A proof-of-principle configuration without an identified testbed is also suggested.
	Slides TUXB01 [1.602 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUXB01
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WEPOW055	Bayesian Optimization of FEL Performance at LCLS	2972
	M.W. McIntire, T.M. Cope, D.F. Ratner SLAC, Menlo Park, California, USA S. Ermon Stanford University, Stanford, California, USA
	Funding: Research is supported by the U.S. Department of Energy under Contract No. DE-AC02-76SF00515. The LCLS free-electron laser at SLAC is tuned via a huge number of parameters such as energy and magnet settings. Much of this tuning, including quadrupole magnet settings, is typically done by hand by the LCLS operators. In this paper we introduce an automated tuning system using Bayesian optimization, and describe its application to the optimization of noisy objectives such as FEL performance. We demonstrate with preliminary results from our implementation at LCLS that this system can improve both the speed of tuning procedures as well as the quality of the resulting solution.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW055
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WEPOY036	Progress in Automatic Software-based Optimization of Accelerator Performance	3064
	S.I. Tomin, G. Geloni XFEL. EU, Hamburg, Germany I.V. Agapov, I. Zagorodnov DESY, Hamburg, Germany W.S. Colocho, T.M. Cope, A.B. Egger, D.F. Ratner SLAC, Menlo Park, California, USA Y.A. Fomin, Y.V. Krylov, A.G. Valentinov NRC, Moscow, Russia
	Funding: partial support from Ioffe Roentgen Institute grant EDYN EMRAD For modern linac- and storage-ring-based light sources certain amount of empirical tuning is used to reach ultimate performance. The possibility to perform such empirical tuning by automatic methods has now been demonstrated by several authors (e.g. I.Agapov et al. in proc IPAC 2015). In this paper we present the progress in development of our automatic optimisation software based on OCELOT and its applications to SASE FEL optimization at FLASH and LCLS, and its potential for storage ring optimization.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY036
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Paper

Title

Page

LCLS Bunch Compressor Configuration Study for Soft X-ray Operation

1037

S. Li, Y. Ding, Z. Huang, A. Marinelli, T.J. Maxwell, D.F. Ratner, F. Zhou
SLAC, Menlo Park, California, USA
C. Behrens
DESY, Hamburg, Germany

The microbunching instability (MBI) is a well-known problem for high brightness electron beams and has been observed at accelerator facilities around the world. Free-electron lasers (FELs) are particularly susceptible to MBI, which can distort the longitudinal phase space and increase the beam's slice energy spread (SES). Past studies of MBI at the Linac Coherent Light Source (LCLS) relied on optical transition radiation to infer the existence of microbunching. With the development of the x-band transverse deflecting cavity (XTCAV), we can for the first time directly image the longitudinal phase space at the end of the accelerator and complete a comprehensive study of MBI, revealing both detailed MBI behavior as well as insights into mitigation schemes [1]. The fine time resolution of the XTCAV also provides the first LCLS measurements of the final SES, a critical parameter for many advanced FEL schemes. Detailed MBI and SES measurements can aid in understanding MBI mechanisms, benchmarking simulation codes, and designing future high-brightness accelerators.

Slides TUOCA01 [4.436 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOCA01

Export •

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

TUXB01

High Power Radiation Sources using the Steady-state Microbunching Mechanism

1048

A. Chao, E. Granados, X. Huang, D.F. Ratner
SLAC, Menlo Park, California, USA
H.W. Luo
NTHU, Hsinchu, Taiwan

The mechanism of steady-state microbunching (SSMB) was proposed for providing high power coherent radiation using electron storage rings. The mechanism follows closely the RF bunching in conventional storage rings, except that the energy modulation of by an RF system at a microwave wavelength is replaced by a seeded laser in an undulator at an optical wavelength. No FEL mechanism, and thus no FEL energy heating, is invoked. The basic idea is firstly to make the beam microbunched so that its radiation becomes coherent, and secondly to make the microbunching a steady state so that the coherent radiation is maintained at every turn. The combination of the high repetition rate of a storage ring and the enhanced radiation power by a factor of N (the number of electrons in the microbunches within one coherence length) opens the possibility as well as challenges of very high power SSMB sources. To explore its potential reach, we apply SSMB to the infrared, deep ultraviolet and EUV regions and estimate their respective power levels using SPEAR3 as example. Several variants of the SSMB schemes are discussed. A proof-of-principle configuration without an identified testbed is also suggested.

Slides TUXB01 [1.602 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUXB01

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WEPOW055

Bayesian Optimization of FEL Performance at LCLS

2972

M.W. McIntire, T.M. Cope, D.F. Ratner
SLAC, Menlo Park, California, USA
S. Ermon
Stanford University, Stanford, California, USA

Funding: Research is supported by the U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
The LCLS free-electron laser at SLAC is tuned via a huge number of parameters such as energy and magnet settings. Much of this tuning, including quadrupole magnet settings, is typically done by hand by the LCLS operators. In this paper we introduce an automated tuning system using Bayesian optimization, and describe its application to the optimization of noisy objectives such as FEL performance. We demonstrate with preliminary results from our implementation at LCLS that this system can improve both the speed of tuning procedures as well as the quality of the resulting solution.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW055

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WEPOY036

Progress in Automatic Software-based Optimization of Accelerator Performance

3064

S.I. Tomin, G. Geloni
XFEL. EU, Hamburg, Germany
I.V. Agapov, I. Zagorodnov
DESY, Hamburg, Germany
W.S. Colocho, T.M. Cope, A.B. Egger, D.F. Ratner
SLAC, Menlo Park, California, USA
Y.A. Fomin, Y.V. Krylov, A.G. Valentinov
NRC, Moscow, Russia

Funding: partial support from Ioffe Roentgen Institute grant EDYN EMRAD
For modern linac- and storage-ring-based light sources certain amount of empirical tuning is used to reach ultimate performance. The possibility to perform such empirical tuning by automatic methods has now been demonstrated by several authors (e.g. I.Agapov et al. in proc IPAC 2015). In this paper we present the progress in development of our automatic optimisation software based on OCELOT and its applications to SASE FEL optimization at FLASH and LCLS, and its potential for storage ring optimization.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY036

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