IPAC2016 - List of Authors (Emma, P.)

Paper	Title	Page
MOPOW045	Measurement of Advanced Dispersion-based Beam-tilt Correction	813
	M.W. Guetg, F.-J. Decker, Y. Ding, P. Emma, Z. Huang, T.J. Maxwell SLAC, Menlo Park, California, USA
	Funding: DOE contract \#DE-AC02-76SF00515 Free electron lasers in the X-ray regime require a good slice alignment along the electron bunch to achieve their best performance. A transverse beam slice shift reduces this alignment and spoils projected emittance and optics matching. Coherent synchrotron radiation, specifically for over-compression going through full compression, and transverse wakefields are major contributors to this. In the case of the large-bandwidth operation, with a strong energy chirp on the bunch, this misalignments furthermore reduce the spectral bandwidth of the FEL pulse. Well-defined manipulation of dispersion allows to compensate for this slice centroid shifts, therefore enhancing lasing power and in case of the large bandwidth mode, spectral bandwidth. This work shows the first application of this correction on an X-ray FEL resulting in increase in beam-power and bandwidth.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW045
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MOPOW048	Development of the LCLS-II Optics Design	820
	Y. Nosochkov, P. Emma, T.O. Raubenheimer, M. Woodley SLAC, Menlo Park, California, USA
	Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515. The LCLS-II is a high repetition rate, high average brightness free-electron laser (FEL) under construction at the SLAC National Accelerator Laboratory. The LCLS-II will include new major components: a high repetition-rate injector, a superconducting, CW (continuous wave), 4-GeV linac with a bunch compressor system, a 3-way beam spreader, with independent hard X-ray (HXR) and soft X-ray (SXR) FEL undulators. The design is based on the existing SLAC facilities, including the LCLS linac and beam transport lines. The new SXR line will utilize a variable-gap undulator sharing the same tunnel with the new HXR horizontal-gap vertically polarizing undulator that will replace the existing LCLS undulator. We describe the current state of the electron optics design and the latest developments.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW048
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TUPOR018	Design Optimization of Compensation Chicanes in the LCLS-II Transport Lines	1695
	J. Qiang, C.E. Mitchell, M. Venturini LBNL, Berkeley, California, USA Y. Ding, P. Emma, Z. Huang, G. Marcus, Y. Nosochkov, T.O. Raubenheimer, L. Wang, M. Woodley SLAC, Menlo Park, California, USA
	LCLS-II is a 4th-generation high-repetition rate Free Electron Laser (FEL) based x-ray light source to be built at the SLAC National Accelerator Laboratory. To mitigate the microbunching instability, the transport lines from the exit of the Linac to the undulators will include a number of weak compensation chicanes with the purpose of cancelling the momentum compaction generated by the main bend magnets of the transport lines. In this paper, we will report on our design optimization study of these compensation chicanes in the presence of both longitudinal and transverse space-charge effects.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR018
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TUPOR019	RF Injector Beam Dynamics Optimization and Injected Beam Energy Constraints for LCLS-II	1699
	C.E. Mitchell, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini LBNL, Berkeley, California, USA P. Emma, T.O. Raubenheimer, J.F. Schmerge, F. Zhou SLAC, Menlo Park, California, USA
	Funding: Work supported by the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231. LCLS-II is a proposed high-repetition rate (>1 MHz) Free Electron Laser (FEL) X-ray light source, based on a CW, superconducting linac, to be built at SLAC National Accelerator Laboratory. The injector technology is based on a high-repetition rate RF photoinjector gun developed as part of the Advanced Photoinjector Experiment (APEX) at Lawrence Berkeley National Laboratory. Exploration of the injector design settings is performed using a multiobjective genetic optimizer to optimize the beam quality at the injector exit (~100 MeV). In this paper, we describe the current status of LCLS-II injector design optimization, with a focus on the sensitivity of the optimized solutions to the beam energy at the injector exit, which is constrained by the requirements of the downstream laser heater system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR019
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TUPOW030	A CW Normal Conducting RF Cavity for Fast Chirp Control in the LCLS-II	1817
	M.H. Nasr, P. Emma, S.G. Tantawi SLAC, Menlo Park, California, USA
	The LCLS-II is a high repetition-rate Free-Electron Laser (FEL) facility under construction at SLAC. A new 4-GeV continuous wave (CW) superconducting (SC) L-band linac is being built to provide an electron bunch rate of up to 1 MHz, with bunches rapidly switched between two FEL undulators. It is desirable to provide peak current (i.e., pulse length) control in each FEL independently by varying the RF phase (chirp) prior to the first bunch compressor. However, the high-Q, SCRF, with its 1-ms fill-time, cannot be changed within one bunch spacing (1 us). So to provide a small chirp adjustment from bunch to bunch, we propose a short CW copper RF accelerating cavity, located just after the injector, with < 250-ns fill-time designed to adjust the beam chirp at zero-crossing phase. We examined RF cavity designs spanning RF frequencies from L-band to X-band. We considered both SW and TW structures. We found an optimal solution with 2 cm iris diameter, SW RF cavity, operating at C-band with input power of only 10 kW. If one can afford to operate with smaller diameter, from a wakefield point of view, then similar structure at X-band may require only 500 W with 5 mm iris diameter.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW030
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THPMY043	Collimation System Design for LCLS-II	3755
	M.W. Guetg, P. Emma, M. Santana-Leitner, J.J. Welch, F. Zhou SLAC, Menlo Park, California, USA
	Funding: DOE contract \#DE-AC02-76SF00515 The planned LCLS-II FEL has an average beam power of up to 1.2 MW and a repetition rate of up to 1 MHz, both of which entail serious challenges for beam halo collimation. This paper summarizes the efforts to assess the proposed collimation system. The undulator section is specifically focused on due to its high loss sensitivity (maximal 12 mW). This proceedings concentrate on field emissions of the gun. Different dark current distribution, linac configurations and simulation programs were used to increase assurance of the results. Filled phase-space tracking further supplemented an independent prove of the collimation system effectiveness and expands to include beam-halo originating from different sources than the gun.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY043
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Paper

Title

Page

Measurement of Advanced Dispersion-based Beam-tilt Correction

813

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

Funding: DOE contract \#DE-AC02-76SF00515
Free electron lasers in the X-ray regime require a good slice alignment along the electron bunch to achieve their best performance. A transverse beam slice shift reduces this alignment and spoils projected emittance and optics matching. Coherent synchrotron radiation, specifically for over-compression going through full compression, and transverse wakefields are major contributors to this. In the case of the large-bandwidth operation, with a strong energy chirp on the bunch, this misalignments furthermore reduce the spectral bandwidth of the FEL pulse. Well-defined manipulation of dispersion allows to compensate for this slice centroid shifts, therefore enhancing lasing power and in case of the large bandwidth mode, spectral bandwidth. This work shows the first application of this correction on an X-ray FEL resulting in increase in beam-power and bandwidth.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW045

Export •

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

MOPOW048

Development of the LCLS-II Optics Design

820

Y. Nosochkov, P. Emma, T.O. Raubenheimer, M. Woodley
SLAC, Menlo Park, California, USA

Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515.
The LCLS-II is a high repetition rate, high average brightness free-electron laser (FEL) under construction at the SLAC National Accelerator Laboratory. The LCLS-II will include new major components: a high repetition-rate injector, a superconducting, CW (continuous wave), 4-GeV linac with a bunch compressor system, a 3-way beam spreader, with independent hard X-ray (HXR) and soft X-ray (SXR) FEL undulators. The design is based on the existing SLAC facilities, including the LCLS linac and beam transport lines. The new SXR line will utilize a variable-gap undulator sharing the same tunnel with the new HXR horizontal-gap vertically polarizing undulator that will replace the existing LCLS undulator. We describe the current state of the electron optics design and the latest developments.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW048

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TUPOR018

Design Optimization of Compensation Chicanes in the LCLS-II Transport Lines

1695

J. Qiang, C.E. Mitchell, M. Venturini
LBNL, Berkeley, California, USA
Y. Ding, P. Emma, Z. Huang, G. Marcus, Y. Nosochkov, T.O. Raubenheimer, L. Wang, M. Woodley
SLAC, Menlo Park, California, USA

LCLS-II is a 4th-generation high-repetition rate Free Electron Laser (FEL) based x-ray light source to be built at the SLAC National Accelerator Laboratory. To mitigate the microbunching instability, the transport lines from the exit of the Linac to the undulators will include a number of weak compensation chicanes with the purpose of cancelling the momentum compaction generated by the main bend magnets of the transport lines. In this paper, we will report on our design optimization study of these compensation chicanes in the presence of both longitudinal and transverse space-charge effects.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR018

Export •

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

TUPOR019

RF Injector Beam Dynamics Optimization and Injected Beam Energy Constraints for LCLS-II

1699

C.E. Mitchell, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini
LBNL, Berkeley, California, USA
P. Emma, T.O. Raubenheimer, J.F. Schmerge, F. Zhou
SLAC, Menlo Park, California, USA

Funding: Work supported by the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
LCLS-II is a proposed high-repetition rate (>1 MHz) Free Electron Laser (FEL) X-ray light source, based on a CW, superconducting linac, to be built at SLAC National Accelerator Laboratory. The injector technology is based on a high-repetition rate RF photoinjector gun developed as part of the Advanced Photoinjector Experiment (APEX) at Lawrence Berkeley National Laboratory. Exploration of the injector design settings is performed using a multiobjective genetic optimizer to optimize the beam quality at the injector exit (~100 MeV). In this paper, we describe the current status of LCLS-II injector design optimization, with a focus on the sensitivity of the optimized solutions to the beam energy at the injector exit, which is constrained by the requirements of the downstream laser heater system.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR019

Export •

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

TUPOW030

A CW Normal Conducting RF Cavity for Fast Chirp Control in the LCLS-II

1817

M.H. Nasr, P. Emma, S.G. Tantawi
SLAC, Menlo Park, California, USA

The LCLS-II is a high repetition-rate Free-Electron Laser (FEL) facility under construction at SLAC. A new 4-GeV continuous wave (CW) superconducting (SC) L-band linac is being built to provide an electron bunch rate of up to 1 MHz, with bunches rapidly switched between two FEL undulators. It is desirable to provide peak current (i.e., pulse length) control in each FEL independently by varying the RF phase (chirp) prior to the first bunch compressor. However, the high-Q, SCRF, with its 1-ms fill-time, cannot be changed within one bunch spacing (1 us). So to provide a small chirp adjustment from bunch to bunch, we propose a short CW copper RF accelerating cavity, located just after the injector, with < 250-ns fill-time designed to adjust the beam chirp at zero-crossing phase. We examined RF cavity designs spanning RF frequencies from L-band to X-band. We considered both SW and TW structures. We found an optimal solution with 2 cm iris diameter, SW RF cavity, operating at C-band with input power of only 10 kW. If one can afford to operate with smaller diameter, from a wakefield point of view, then similar structure at X-band may require only 500 W with 5 mm iris diameter.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW030

Export •

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

THPMY043

Collimation System Design for LCLS-II

3755

M.W. Guetg, P. Emma, M. Santana-Leitner, J.J. Welch, F. Zhou
SLAC, Menlo Park, California, USA

Funding: DOE contract \#DE-AC02-76SF00515
The planned LCLS-II FEL has an average beam power of up to 1.2 MW and a repetition rate of up to 1 MHz, both of which entail serious challenges for beam halo collimation. This paper summarizes the efforts to assess the proposed collimation system. The undulator section is specifically focused on due to its high loss sensitivity (maximal 12 mW). This proceedings concentrate on field emissions of the gun. Different dark current distribution, linac configurations and simulation programs were used to increase assurance of the results. Filled phase-space tracking further supplemented an independent prove of the collimation system effectiveness and expands to include beam-halo originating from different sources than the gun.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY043

Export •

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