FEL2014 - List of Keywords (optics)

Paper	Title	Other Keywords	Page
MOP033	Design, Fabrication, and Performance Tests of Dipole and Quadrupole Magnets for PAL-XFEL	quadrupole, dipole, multipole, undulator	90
	H.S. Suh, M.-H. Cho, S.-H. Jeong, Y.-G. Jung, H.-S. Kang, D.E. Kim, I.S. Ko, H.-G. Lee, S.B. Lee, B.G. Oh, K.-H. Park PAL, Pohang, Kyungbuk, Republic of Korea
	PAL-XFEL is now being constructed in Pohang, Korea. This facility will consist of a 10 GeV linac and five undulator beamlines. As the first phase we will construct one hard X-ray and one soft X-ray beamlines which require 7 different families of dipole magnets, and 11 families of quadrupole magnets. We are designing these magnets with considering the efficient manufacturing and the proper power supplies. In this presentation, we describe the design features of the magnets, the manufacturing, and the thermal analysis with the test results.

MOP090	Soft X-ray Self-seeding Simulation Methods and their Application for LCLS	undulator, radiation, simulation, FEL	264
	S. Serkez DESY, Hamburg, Germany Y. Ding, Z. Huang, J. Krzywinski SLAC, Menlo Park, California, USA
	Self-seeding is a promising approach to significantly narrow the SASE bandwidth of XFELs to produce nearly transform-limited pulses. We study radiation propagation through the grating monochromator installed at LCLS. The monochromator design is based on a toroidal variable line spacing grating working at a fixed incidence angle mounting without an entrance slit. It covers the spectral range from 500eV to 1000eV. The optical system was studied using wave optics method to evaluate the performance of the self-seeding scheme. Our wave optics analysis takes into account the finite size of the coherent source, third-order aberrations and height error of the optical elements. Wave optics is the only method available, in combination with FEL simulations, to simulate performance of the monochromator without exit slit. Two approaches for time-dependent simulations are presented, compared and discussed. Also pulse-front tilt phenomenon effect is illustrated.

TUP049	Storage Ring XFEL with Longitudinal Focusing	FEL, undulator, storage-ring, insertion	492
	I.V. Agapov, G. Geloni XFEL. EU, Hamburg, Germany
	In present work we investigate the possibility of running a high gain FEL on a storage ring using a longitudinally focusing insertion to compress bunches passing an undulator. If integrated into a storage ring similar to PETRA III such device could potentially produce continuous ∼1ps pulses of photons in the nm range with peak pulse powers of tens of GW. Even without operating in FEL saturation mode the longitudinal focusing can provide means to increase the brightness and shorten the photon pulse length

TUP069	Cavity Length Change vs. Mirror Steering in a Ring Confocal Resonator	cavity, wiggler, FEL, operation	516
	S.V. Benson JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-84-ER40150, the Office of Naval Research, and the Joint Technology Office. In principle, a ring confocal resonator allows for the use of a short Rayleigh length without the extreme sensi-tivity to mirror steering typical in a near-concentric reso-nator [1]. One possible weakness of such a resonator is that the cavity length is no longer independent of the mirror steering. This is one of the strengths of a linear resonator. In this presentation, it is shown that, in a simple 2-dimensional corner cube type ring confocal resonator, the cavity length is, in fact, not dependent on the mirror steering to first order in the mirror angles. Thus the ring-confocal resonator might be a very easy-to-operate and stable resonator for short Rayleigh range operation in FEL oscillators [1] Stephen Benson, George Neil, Michelle Shinn, Laser and Beam Control Technologies, Santanu Basu, James Riker, Editors, Proceedings of SPIE Vol. 4632 (2002).

THP002	Beam Energy Management and RF Failure Compensation Scenarios for the European XFEL	linac, klystron, operation, quadrupole	672
	B. Beutner DESY, Hamburg, Germany
	The operation of complex systems as the driver linacs for free-electron-lasers is limited by the reliability of the individual components. Failures of RF systems can therefore constrict FEL availability. Typically reserves are included in the overall linac voltage capacity to allow for redistribution of acceleration in case of an RF failure. However, such redistributions of the acceleration of the linac affects the beam dynamics of the machine. While the effects on the optics can easily be compensated by rescaling of the quadrupole magnet strength, the bunch compression set-up requires a more involved investigation. In this paper we discuss studies for an energy management system for the European XFEL.

THP032	Effects of Potential Energy Spread on Particle Dynamics in Magnetic Bending Systems	transverse-dynamics, space-charge, electron, simulation	779
	R. Li JLab, Newport News, Virginia, USA
	Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Understanding CSR effects for the generation and transport of high brightness electron beams is crucial for designs of modern FELs. Most studies of CSR effects focus on the impacts of the longitudinal CSR wakefield. In this study, we investigate the impact of the initial retarded potential energy of particles, due to bunch collective interaction, on the transverse dynamics of particles on a curved orbit. It is shown that as part of the remnants of the CSR cancellation effect when both the longitudinal and transverse CSR fores are taken into account, this initial potential energy at the entrance of a bending system acts as a pseudo kinetic energy, or pseudo energy in short, because its effect on particle optics through dispersion and momentum compaction is indistinguishable from effect of the usual kinetic energy offset from the design energy. Our estimation indicates that the resulting effect of pseudo energy spread can be measurable only when the peak current of the bunch is high enough such that the slice pseudo energy spread is appreciable compared to the slice kinetic energy spread. The implication of this study on simulations and experiments of CSR effects will be discussed.

THP073	Optics Measurements at FLASH2	extraction, undulator, linac, emittance	902
	M. Scholz, B. Faatz, M. Vogt, J. Zemella DESY, Hamburg, Germany
	FLASH2 is a newly build second beam line at FLASH, the soft X-ray FEL at DESY, Hamburg. Unlike the existing beam line FLASH1, it is equipped with variable gap undulators. This beam line is currently being commissioned. Both undulator beam lines of FLASH are driven by a common linear accelerator. Fast kickers and a septum are installed at the end of the linac to distribute the electron bunches of every train between FLASH1 and FLASH2. A specific beam optic in the extraction arc with horizontal beam waists in the bending magnets is mandatory in order to mitigate CSR effects. Here we will show first results of measurements and compare to simulations.

THP082	Measurements of Compressed Bunch Temporal Profile using Electro-Optic Monitor at SITF	laser, electron, vacuum, diagnostics	922
	Ye. Ivanisenko, V. Schlott PSI, Villigen PSI, Switzerland P. Peier DESY, Hamburg, Germany
	Funding: The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n.°290605 (PSI-FELLOW/COFUND) The SwissFEL Injector Test Facility (SITF) is an electron linear accelerator with a single bunch compression stage at Paul Scherrer Institute (PSI) in Switzerland. Electro-optic monitors (EOMs) are available for bunch temporal profile measurements before and after the bunch compressor. The profile reconstruction is based upon spectral decoding technique. This diagnostic method is non-invasive, compact and cost-effective. It does not have high resolution and wide dynamic range of an RF transverse deflecting structure (TDS), but it is free of transverse beam size influence, what makes it a perfect tool for fast compression tuning. We present results of EOM and TDS measurements with down to 150 fs long bunches after the compression stage at SITF.

THP088	Comparison of Quadrupole Scan and Multi-screen Method for the Measurement of Projected and Slice Emittance at the SwissFEL Injector Test Facility	emittance, quadrupole, diagnostics, FEL	941
	M. Yan, B. Beutner, C. Gerth DESY, Hamburg, Germany R. Ischebeck, E. Prat PSI, Villigen PSI, Switzerland
	High-brightness electron bunches with small transverse emittance are required to drive X-ray free-electron lasers (FELs). For the measurement of the transverse emittance, the quadrupole scan and multi-screen methods are the two most common procedures. By employing a transverse deflecting structure, the measurement of the slice emittance becomes feasible. The quadrupole scan is more flexible in freely choosing the data points during the scan, while the multi-screen method allows on-line emittance measurements utilising off-axis screens in combination with fast kicker magnets. The latter is especially the case for high-repetition multi-bunch FELs, such as the European XFEL, which offer the possibility of on-line diagnostics. In this paper, we present comparative measurements of projected and slice emittance applying these two methods at the SwissFEL Injector Test Facility and discuss the implementation of on-line diagnostics at the European XFEL.

THP092	Transition Radiation of an Electron Bunch and Imprint of Lorentz-Covariance and Temporal-Causality	electron, radiation, diagnostics, simulation	952
	G.L. Orlandi PSI, Villigen PSI, Switzerland
	The study of Transition Radiation (TR) of a bunch of N electrons offers a precious insight into the role that Lorentz-covariance and temporal-causality play in an electromagnetic radiative mechanism of a relativistic beam. The contributions of the N single electrons to the radiation field are indeed characterized by emission phases from the metallic surface which are in a causality relation with the temporal sequence of the N particle collisions onto the radiating screen. The Lorentz-covariance characterizing the virtual quanta field of the relativistic charge is also expected to imprint the radiation field and the related energy spectrum. The main aspects of a Lorentz-covariance and temporal-causality consistent formulation of the TR energy spectrum of an electron bunch will be described.

THC03	Suppression of the CSR-induced Emittance Growth in Achromats using Two-dimensional point-kick Analysis	dipole, emittance, simulation, linear-collider	976
	Y. Jiao, X. Cui, X.Y. Huang, G. Xu IHEP, Beijing, People's Republic of China
	Coherent synchrotron radiation (CSR) effect causes transverse emittance dilution in high-brightness light sources and linear colliders. Suppression of the emittance growth induced by CSR is essential and critical to preserve the beam quality and to help improve the machine performance. To evaluate the CSR effect analytically, we propose a novel method, named “two-dimensional point-kick analysis”. In this method, the CSR-induced emittance growth in an n-dipole achromat can be evaluated with the analysis of only the motion of particle in (x, x') two-dimensional plane with n-point kicks, which can be, to a large extent, counted separately. To demonstrate the effectiveness of this method, the CSR effect in a two-diople achromat and a symmetric TBA is studied, and generic conditions of suppressing the CSR-induced emittance growth, which are independent of concrete element parameters and are robust against the variation of initial beam distribution, are found. These conditions are verified with the ELEGANT simulations and can be rather easily applied to real machines.
	Slides THC03 [1.941 MB]

FRA04	Optimization of High Average Power FEL Beam for EUV Lithography Application	FEL, laser, electron, plasma	990
	A. Endo, K. Sakaue, M. Washio Waseda University, Tokyo, Japan H. Mizoguchi Gigaphoton Inc, Hiratsuka, Kanagawa, Japan
	Extreme Ultraviolet Lithography (EUVL) is realized with 100W plasma EUV source at 13.5nm. It is recommended by the EUVL community to evaluate an alternative approach based on high repetition rate FEL, to avoid the power limit of the plasma source. Several papers discuss on the possibility to realize superconducting FEL to generate multiple kW 13.5nm light. We must notice that the present SASE FEL pulse has higher beam fluence than the resist ablation threshold, and high spatial coherence which results in speckle patterns, and random longitudinal mode beat which leads to high peak powerμspikes. An expanding mirror is installed after the undulator to reduce the beam fluence, external-seeding configuration is employed to reduce the longitudinal mode beat, and total reflection beam homogenizer is used for spatial mode mixing. Pulse repetition rate is more than 3MHz to cancel the speckle patter formation by averaging illumination. This paper discusses on the lowest risk approach to construct a prototype to demonstrate a high average power 13.5nm FEL for the best optimization in EUVL application, including the scaling to 6.7nm wavelength. J. Chalupský, L. Juha et.al, “Characteristics of focused soft X-ray free-electron laser beam determined by ablation of organic molecular solids”, OPTICS EXPRESS 15, 6036 (2007)
	Slides FRA04 [1.413 MB]

Paper

Title

Other Keywords

Page

MOP033

Design, Fabrication, and Performance Tests of Dipole and Quadrupole Magnets for PAL-XFEL

quadrupole, dipole, multipole, undulator

90

H.S. Suh, M.-H. Cho, S.-H. Jeong, Y.-G. Jung, H.-S. Kang, D.E. Kim, I.S. Ko, H.-G. Lee, S.B. Lee, B.G. Oh, K.-H. Park
PAL, Pohang, Kyungbuk, Republic of Korea

PAL-XFEL is now being constructed in Pohang, Korea. This facility will consist of a 10 GeV linac and five undulator beamlines. As the first phase we will construct one hard X-ray and one soft X-ray beamlines which require 7 different families of dipole magnets, and 11 families of quadrupole magnets. We are designing these magnets with considering the efficient manufacturing and the proper power supplies. In this presentation, we describe the design features of the magnets, the manufacturing, and the thermal analysis with the test results.

MOP090

Soft X-ray Self-seeding Simulation Methods and their Application for LCLS

undulator, radiation, simulation, FEL

264

S. Serkez
DESY, Hamburg, Germany
Y. Ding, Z. Huang, J. Krzywinski
SLAC, Menlo Park, California, USA

Self-seeding is a promising approach to significantly narrow the SASE bandwidth of XFELs to produce nearly transform-limited pulses. We study radiation propagation through the grating monochromator installed at LCLS. The monochromator design is based on a toroidal variable line spacing grating working at a fixed incidence angle mounting without an entrance slit. It covers the spectral range from 500eV to 1000eV. The optical system was studied using wave optics method to evaluate the performance of the self-seeding scheme. Our wave optics analysis takes into account the finite size of the coherent source, third-order aberrations and height error of the optical elements. Wave optics is the only method available, in combination with FEL simulations, to simulate performance of the monochromator without exit slit. Two approaches for time-dependent simulations are presented, compared and discussed. Also pulse-front tilt phenomenon effect is illustrated.

TUP049

Storage Ring XFEL with Longitudinal Focusing

FEL, undulator, storage-ring, insertion

492

I.V. Agapov, G. Geloni
XFEL. EU, Hamburg, Germany

In present work we investigate the possibility of running a high gain FEL on a storage ring using a longitudinally focusing insertion to compress bunches passing an undulator. If integrated into a storage ring similar to PETRA III such device could potentially produce continuous ∼1ps pulses of photons in the nm range with peak pulse powers of tens of GW. Even without operating in FEL saturation mode the longitudinal focusing can provide means to increase the brightness and shorten the photon pulse length

TUP069

Cavity Length Change vs. Mirror Steering in a Ring Confocal Resonator

cavity, wiggler, FEL, operation

516

S.V. Benson
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-84-ER40150, the Office of Naval Research, and the Joint Technology Office.
In principle, a ring confocal resonator allows for the use of a short Rayleigh length without the extreme sensi-tivity to mirror steering typical in a near-concentric reso-nator [1]. One possible weakness of such a resonator is that the cavity length is no longer independent of the mirror steering. This is one of the strengths of a linear resonator. In this presentation, it is shown that, in a simple 2-dimensional corner cube type ring confocal resonator, the cavity length is, in fact, not dependent on the mirror steering to first order in the mirror angles. Thus the ring-confocal resonator might be a very easy-to-operate and stable resonator for short Rayleigh range operation in FEL oscillators
[1] Stephen Benson, George Neil, Michelle Shinn, Laser and Beam Control Technologies, Santanu Basu, James Riker, Editors, Proceedings of SPIE Vol. 4632 (2002).

THP002

Beam Energy Management and RF Failure Compensation Scenarios for the European XFEL

linac, klystron, operation, quadrupole

672

B. Beutner
DESY, Hamburg, Germany

The operation of complex systems as the driver linacs for free-electron-lasers is limited by the reliability of the individual components. Failures of RF systems can therefore constrict FEL availability. Typically reserves are included in the overall linac voltage capacity to allow for redistribution of acceleration in case of an RF failure. However, such redistributions of the acceleration of the linac affects the beam dynamics of the machine. While the effects on the optics can easily be compensated by rescaling of the quadrupole magnet strength, the bunch compression set-up requires a more involved investigation. In this paper we discuss studies for an energy management system for the European XFEL.

THP032

Effects of Potential Energy Spread on Particle Dynamics in Magnetic Bending Systems

transverse-dynamics, space-charge, electron, simulation

779

R. Li
JLab, Newport News, Virginia, USA

Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Understanding CSR effects for the generation and transport of high brightness electron beams is crucial for designs of modern FELs. Most studies of CSR effects focus on the impacts of the longitudinal CSR wakefield. In this study, we investigate the impact of the initial retarded potential energy of particles, due to bunch collective interaction, on the transverse dynamics of particles on a curved orbit. It is shown that as part of the remnants of the CSR cancellation effect when both the longitudinal and transverse CSR fores are taken into account, this initial potential energy at the entrance of a bending system acts as a pseudo kinetic energy, or pseudo energy in short, because its effect on particle optics through dispersion and momentum compaction is indistinguishable from effect of the usual kinetic energy offset from the design energy. Our estimation indicates that the resulting effect of pseudo energy spread can be measurable only when the peak current of the bunch is high enough such that the slice pseudo energy spread is appreciable compared to the slice kinetic energy spread. The implication of this study on simulations and experiments of CSR effects will be discussed.

THP073

Optics Measurements at FLASH2

extraction, undulator, linac, emittance

902

M. Scholz, B. Faatz, M. Vogt, J. Zemella
DESY, Hamburg, Germany

FLASH2 is a newly build second beam line at FLASH, the soft X-ray FEL at DESY, Hamburg. Unlike the existing beam line FLASH1, it is equipped with variable gap undulators. This beam line is currently being commissioned. Both undulator beam lines of FLASH are driven by a common linear accelerator. Fast kickers and a septum are installed at the end of the linac to distribute the electron bunches of every train between FLASH1 and FLASH2. A specific beam optic in the extraction arc with horizontal beam waists in the bending magnets is mandatory in order to mitigate CSR effects. Here we will show first results of measurements and compare to simulations.

THP082

Measurements of Compressed Bunch Temporal Profile using Electro-Optic Monitor at SITF

laser, electron, vacuum, diagnostics

922

Ye. Ivanisenko, V. Schlott
PSI, Villigen PSI, Switzerland
P. Peier
DESY, Hamburg, Germany

Funding: The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n.°290605 (PSI-FELLOW/COFUND)
The SwissFEL Injector Test Facility (SITF) is an electron linear accelerator with a single bunch compression stage at Paul Scherrer Institute (PSI) in Switzerland. Electro-optic monitors (EOMs) are available for bunch temporal profile measurements before and after the bunch compressor. The profile reconstruction is based upon spectral decoding technique. This diagnostic method is non-invasive, compact and cost-effective. It does not have high resolution and wide dynamic range of an RF transverse deflecting structure (TDS), but it is free of transverse beam size influence, what makes it a perfect tool for fast compression tuning. We present results of EOM and TDS measurements with down to 150 fs long bunches after the compression stage at SITF.

THP088

Comparison of Quadrupole Scan and Multi-screen Method for the Measurement of Projected and Slice Emittance at the SwissFEL Injector Test Facility

emittance, quadrupole, diagnostics, FEL

941

M. Yan, B. Beutner, C. Gerth
DESY, Hamburg, Germany
R. Ischebeck, E. Prat
PSI, Villigen PSI, Switzerland

High-brightness electron bunches with small transverse emittance are required to drive X-ray free-electron lasers (FELs). For the measurement of the transverse emittance, the quadrupole scan and multi-screen methods are the two most common procedures. By employing a transverse deflecting structure, the measurement of the slice emittance becomes feasible. The quadrupole scan is more flexible in freely choosing the data points during the scan, while the multi-screen method allows on-line emittance measurements utilising off-axis screens in combination with fast kicker magnets. The latter is especially the case for high-repetition multi-bunch FELs, such as the European XFEL, which offer the possibility of on-line diagnostics. In this paper, we present comparative measurements of projected and slice emittance applying these two methods at the SwissFEL Injector Test Facility and discuss the implementation of on-line diagnostics at the European XFEL.

THP092

Transition Radiation of an Electron Bunch and Imprint of Lorentz-Covariance and Temporal-Causality

electron, radiation, diagnostics, simulation

952

G.L. Orlandi
PSI, Villigen PSI, Switzerland

The study of Transition Radiation (TR) of a bunch of N electrons offers a precious insight into the role that Lorentz-covariance and temporal-causality play in an electromagnetic radiative mechanism of a relativistic beam. The contributions of the N single electrons to the radiation field are indeed characterized by emission phases from the metallic surface which are in a causality relation with the temporal sequence of the N particle collisions onto the radiating screen. The Lorentz-covariance characterizing the virtual quanta field of the relativistic charge is also expected to imprint the radiation field and the related energy spectrum. The main aspects of a Lorentz-covariance and temporal-causality consistent formulation of the TR energy spectrum of an electron bunch will be described.

THC03

Suppression of the CSR-induced Emittance Growth in Achromats using Two-dimensional point-kick Analysis

dipole, emittance, simulation, linear-collider

976

Y. Jiao, X. Cui, X.Y. Huang, G. Xu
IHEP, Beijing, People's Republic of China

Coherent synchrotron radiation (CSR) effect causes transverse emittance dilution in high-brightness light sources and linear colliders. Suppression of the emittance growth induced by CSR is essential and critical to preserve the beam quality and to help improve the machine performance. To evaluate the CSR effect analytically, we propose a novel method, named “two-dimensional point-kick analysis”. In this method, the CSR-induced emittance growth in an n-dipole achromat can be evaluated with the analysis of only the motion of particle in (x, x') two-dimensional plane with n-point kicks, which can be, to a large extent, counted separately. To demonstrate the effectiveness of this method, the CSR effect in a two-diople achromat and a symmetric TBA is studied, and generic conditions of suppressing the CSR-induced emittance growth, which are independent of concrete element parameters and are robust against the variation of initial beam distribution, are found. These conditions are verified with the ELEGANT simulations and can be rather easily applied to real machines.

Slides THC03 [1.941 MB]

FRA04

Optimization of High Average Power FEL Beam for EUV Lithography Application

FEL, laser, electron, plasma

990

A. Endo, K. Sakaue, M. Washio
Waseda University, Tokyo, Japan
H. Mizoguchi
Gigaphoton Inc, Hiratsuka, Kanagawa, Japan

Extreme Ultraviolet Lithography (EUVL) is realized with 100W plasma EUV source at 13.5nm. It is recommended by the EUVL community to evaluate an alternative approach based on high repetition rate FEL, to avoid the power limit of the plasma source. Several papers discuss on the possibility to realize superconducting FEL to generate multiple kW 13.5nm light. We must notice that the present SASE FEL pulse has higher beam fluence than the resist ablation threshold*, and high spatial coherence which results in speckle patterns, and random longitudinal mode beat which leads to high peak powerμspikes. An expanding mirror is installed after the undulator to reduce the beam fluence, external-seeding configuration is employed to reduce the longitudinal mode beat, and total reflection beam homogenizer is used for spatial mode mixing. Pulse repetition rate is more than 3MHz to cancel the speckle patter formation by averaging illumination. This paper discusses on the lowest risk approach to construct a prototype to demonstrate a high average power 13.5nm FEL for the best optimization in EUVL application, including the scaling to 6.7nm wavelength.
*J. Chalupský, L. Juha et.al, “Characteristics of focused soft X-ray free-electron laser beam determined by ablation of organic molecular solids”, OPTICS EXPRESS 15, 6036 (2007)

Slides FRA04 [1.413 MB]